Answer
Option
Question Statistics
Leontiasis Ossea
14%
Hand-Schüller-Christian Disease
68%
McCune-Albright syndrome
4%
Cherubism
8%
Shepherds Crook deformity
5%
Explanation:
This patient has McCune-Albright syndrome
Fibrous dysplasia
This tends to be a condition of childhood-adolescence. It is otherwise rarely seen in patients older than 30. It is a
benign condition caused by abnormal osteoblasts and leading to focal replacement of normal bone with fibrous
tissue. Most cases are monostotic but polyostotic cases occur around 20% of the time. Virtually any bone can be
affected although the long bones tend to be more frequently affected in the polyostotic form. That said, fibrous
dysplasia is also a typical differential diagnosis for a rib or skull lesion.
Classically the appearances on x-ray or CT is described as 'ground glass' in matrix, and situated within the centre
of the bone (i.e. medullary), but often causing bony expansion. Since the bone is abnormal there is an increased
risk of fractures but unless there is an acute injury there should not be a periosteal reaction.
On a nuclear medicine bone scan the lesions tend to show increased uptake and this is therefore rarely useful in
diagnosing this condition.
Aside from pathological fractures, the condition can also occasionally be complicated by secondary
degeneration which would be to osteosarcoma and should be suspected if the patient complains of pain and the
growth of a soft tissue mass. This occurs more frequently in patients who have previously been exposed to
radiation.
There are a number of eponymous or descriptive terms associated with fibrous dysplasia:
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Shepherds crook deformity - coxa varus deformity of the proximal femur. This is usually used to describe the
effect of fibrous dysplasia on the proximal femur with chronic bowing and remodelling secondary to
microfractures, but the same appearance can occur with conditions such as Paget disease or osteogenesis
imperfecta, for the same reasons.
Protrusio acetabuli - fibrous dysplasia is one of a number of things which can cause protrusion of the femoral
head into the pelvis due to remodelling of the acetabulum.
Leontiasis ossea - facial involvement causing a specific appearance said to resemble that of a lion. Owing to
canal stenosis caused by bony expansion patients can exhibit cranial nerve palsies.
Cherubism - facial (maxilla and mandible) involvement causes a specific appearance said to resemble that of a
cherub. Owing to canal stenosis caused by bony expansion patients can exhibit cranial nerve palsies. Cherubism
is inherited in an autosomal dominant fashion.
McCune-Albright syndrome - this almost always only affects girls and consists of a triad of cafe-au-lait spots,
precocious puberty (or other endocrine pathology), and polyostotic fibrous dysplasia. The cafe-au-lait
pigmentation is often on the back and can commonly be seen to respect the midline.
Mazabraud syndrome - this is a very rare condition. Patients present with polyostotic fibrous dysplasia and soft
tissue tumours and are at increased risk of malignant degeneration to osteosarcoma.
Superscan
Metastatic cancer (Prostate, Breast, TCC,
lymphoma)
Renal osteodystrophy
Osteomalacia
Myelofibrosis
Mastocytosis
Paget disease
Mastocytosis
This disease is also caused by clonal proliferation of a particular cell type, however in this case it is of mast cells.
Clinically patients may experience symptoms linked to histamine release from the mast cells such as flushing,
sweating, diarrhoea and abdominal pains but only around a quarter of patients complain of bony pains. The
skeleton can be affected by either focal lesions (usually in the spine) or with diffusely increased density. Other
features such as hepatosplenomegaly, and lymph node enlargement (retroperitoneal, mesenteric, periportal)
may be present too.
Erdheim-Chester disease
Infiltration of the appendicular skeleton by histiocytes leads to fibrosis and sclerosis which can appear striking
on an x-ray. The condition is very similar to Langerhans Cell Histiocytosis (LCH) and both conditions have been
reported across a broad range of patient ages. Usually however LCH presents at around the age of 5-10 whereas
ECD peaks in incidence at around 55 years of age. Both diseases are caused by clonal proliferations of one or
more lines of histiocytes and there are different cellular markers which can help distinguish between the two
diseases pathologically. There is considerable overlap in the clinical and radiological features of both diseases.
Clinically patients with ECD present with all or any of the usual histiocytosis triad of diabetes insipidus,
exophthalmos and bone pain. Of these, the most prominent feature is usually bony pain.
X-rays show sclerosis in the metadiaphyseal regions in a bilateral symmetrical pattern but with sparing of the
epiphyses. Corticomedullary differentiation becomes blurred and there are also multiple areas of lucency
indicating the presence of lytic lesions too.
Metastases
Sclerotic metastases are typical with prostate and breast cancers among others. This should always be
considered as a pertinent differential diagnosis however there are not other features in this question to suggest
it is correct in this case.
Sclerotic metastases:
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Prostate (most common)
Breast (mixed lytic and sclerotic)
Transitional Cell Carcinoma
Lymphoma
Mucinous adenocarcinomas (colon, gastric, ovary)
Medulloblastoma
Neuroblastoma
Carcinoid
Paget disease
Paget disease is seldom found in patients below the age of 50 but is one of the more common musculoskeletal
abnormalities thereafter. It consists of polyostotic, asymmetric disordered bone remodelling where intensive
osteoclastic activity leads to multiple lytic lesions before osteoblastic activity results in the formation of sclerotic
bone. A variety of imaging findings can be seen with x-ray.

Lytic phase: During the lytic phase, radiolucency with a ‘flame’ or ‘blade of grass’ shape extends along the
diaphysis and osteoporosis circumscripta (large lucent areas of skull) can be found in the skull.
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Mixed phase: lytic and sclerotic phenomena
Sclerotic phase: densely sclerotic bone such as the classical ‘ivory vertebra’ can be found.
Clinically it can be an incidental asymptomatic diagnosis or can present as all or any of:
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Elevated ALP with a normal calcium and phosphate
A pathological fracture – although it may be sclerotic, the bone structure is disordered and therefore weaker
than normal bone.
Cranial nerve palsies – due to compression at neural foramina
Enlarging head / hat size – due to widening of the diploic spaces (referred to as the Tam O’Shanter sign,
whereby the skull takes on the appearance of a the Scottish hat called the Tam O’Shanter)
High output cardiac failure – this is a rare presentation caused by markedly increased bony perfusion
Pain – in the absence of a fracture, it is usually not a painful condition per se but can co-exist with other
conditions such as osteoarthritis which may be the cause of the patient’s pain
Radiologically the hallmarks are bony expansion with coarsening of the trabeculae and cortices. On a bone scan
active lesions will show increased uptake due to their increased blood flow.
Sarcomatous degeneration of the affected sites into either an osteosarcoma, malignant fibrous histiocytoma or
chondrosarcoma carries a poor prognosis and careful study should be made of any known lesions at each
imaging opportunity. New soft tissue component formation or new lysis of previously sclerotic bone should raise
suspicion.
Of note, in an adult the avulsion of the lesser trochanter suggests a metastasis, not a musculoskeletal injury.
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ASIS
Apophyseal injuries
Sartorius
AIIS
Rectus femoris (straight head)
Pubic ramus
Adductors, gracilis
Lesser trochanter
Iliopsoas
Ischial tuberosity
Hamstrings
Causes of bone infarction:
Sickle cell disease
Excess corticosteroid
Pancreatitis
Caisson disease ‘The Bends’
Gaucher disease
Leukemia/lymphoma
Medullary osteonecrosis can be secondary to anything leading to vascular compromise and has the propensity
to lead to severe loss or architecture and loss of function, not to mention pain, to the patient. It is an important
diagnosis to make. On plain film the finding is usually of a lucent area with a sclerotic serpiginous border of
granulation tissue. On MRI this serpiginous border returns low signal on T1 and a ‘double-line’ sign on T2 (high
signal of granulation tissue surrounded by low signal of sclerosis). Strangely enough, centrally within the
infarction the signal retains the characteristics of normal fatty marrow.
Hypertrophic pulmonary osteoarthropathy (HPOA)
In essence this is a paraneoplastic phenomenon although it can be found in many non-neoplastic circumstances.
Subperiosteal new bone formation is seen as a lamellar periosteal reaction on imaging. HPOA is usually
described in the distal phalanges in association with clubbing but does also occur in the rest of the appendicular
skeleton. Clinically the patient may experience a burning pain with swelling and stiffness of any of the affected
joints.
HPOA can be caused by the presence of a bronchogenic carcinoma: this is a common scenario of medical school
finals MCQs. Pleural fibromas are also a known cause. Extra-pulmonary causes are less common but do happen
Fibrous dysplasia
This tends to be a condition of childhood-adolescence. It is otherwise rarely seen in patients older than 30. It is a
benign condition caused by abnormal osteoblasts and leading to focal replacement of normal bone with fibrous
tissue. Most cases are monostotic but polyostotic cases occur around 20% of the time. Virtually any bone can be
affected although the long bones tend to be more frequently affected in the polyostotic form. That said, fibrous
dysplasia is also a typical differential diagnosis for a rib or skull lesion.
Classically the appearances on x-ray or CT is described as 'ground glass' in matrix, and situated within the centre
of the bone (i.e. medullary), but often causing bony expansion. Since the bone is abnormal there is an increased
risk of fractures but unless there is an acute injury there should not be a periosteal reaction.
On a nuclear medicine bone scan the lesions tend to show increased uptake and this is therefore rarely useful in
diagnosing this condition.
Aside from pathological fractures, the condition can also occasionally be complicated by secondary
degeneration which would be to osteosarcoma and should be suspected if the patient complains of pain and the
growth of a soft tissue mass. This occurs more frequently in patients who have previously been exposed to
radiation.
There are a number of eponymous or descriptive terms associated with fibrous dysplasia:






Shepherds crook deformity - coxa varus deformity of the proximal femur. This is usually used to describe the
effect of fibrous dysplasia on the proximal femur with chronic bowing and remodelling secondary to
microfractures, but the same appearance can occur with conditions such as Paget disease or osteogenesis
imperfecta, for the same reasons.
Protrusio acetabuli - fibrous dysplasia is one of a number of things which can cause protrusion of the femoral
head into the pelvis due to remodelling of the acetabulum.
Leontiasis ossea - facial involvement causing a specific appearance said to resemble that of a lion. Owing to
canal stenosis caused by bony expansion patients can exhibit cranial nerve palsies.
Cherubism - facial (maxilla and mandible) involvement causes a specific appearance said to resemble that of a
cherub. Owing to canal stenosis caused by bony expansion patients can exhibit cranial nerve palsies. Cherubism
is inherited in an autosomal dominant fashion.
McCune-Albright syndrome - this almost always only affects girls and consists of a triad of cafe-au-lait spots,
precocious puberty (or other endocrine pathology), and polyostotic fibrous dysplasia. The cafe-au-lait
pigmentation is often on the back and can commonly be seen to respect the midline.
Mazabraud syndrome - this is a very rare condition. Patients present with polyostotic fibrous dysplasia and soft
tissue tumours and are at increased risk of malignant degeneration to osteosarcoma.
Hand-Schüller-Christian Disease – classically a triad of destructive bony lesions, diabetes insipidus and
exophthalmos is a type of histiocytosis. In a quarter of these patients the lungs are involved with cyst formation
and spontaneous pneumothoraces possible. Nodule formation, fibrosis and honeycombing are also seen.
Sclerotic metastases:








Prostate (most common)
Breast (mixed lytic and sclerotic)
Transitional Cell Carcinoma
Lymphoma
Mucinous adenocarcinomas (colon, gastric, ovary)
Medulloblastoma
Neuroblastoma
Carcinoid
Explanation:
A metastatic deposit within a bone usually returns little signal on T1,
in contrast to the normal high T1 fatty marrow of normal bone, and
high signal on T2. The signal does not drop out on STIR sequences
because the fatty marrow is replaced by tumour so there is no fat signal
to suppress.
------------------------------------------Metastases
Bone marrow on MRI
T1
T2
Normal bone marrow
High (fatty)
Very high and
homogenous
High
Low but enhances
with Gadolinium
Intermediate
Intermediate (initially high
due to oedema)
High
Low
Low
Post-Radiotherapy
Haemangioma
Abnormal bone (metastases,
myeloma, regeneration)
Blastic metastases (prostate, breast,
TCC) and myelofibrosis
High (fluid)
Normally metastatic deposits in the spine lead to low T1 signal and high T2
signal. There should be no signal drop out on fat saturated sequences in
contrast to marrow reconversion where although red marrow will experience
far less signal dropout than yellow marrow, there will still be some loss in
signal owing to the fat content of both types of marrow.
Sclerotic or blastic metastases return little signal on either T1 or T2 weighted
sequences. These include prostate, breast or TCC metastases among others.
Lytic metastases are more likely than sclerotic metastases to enhance with
contrast. Similarly on DWI imaging, whereas lytic metastases will usually
appear hyperintense, sclerotic metastases return little signal since they
contain little water.
Age
Birth
Adolescence
Adulthood
Marrow
Largely red marrow with low fat content → looks like skeletal muscle i.e low on T1
Yellow marrow at the diaphyses
→ high on T1
Red marrow with low fat content
→ low to iso on T1
Largely yellow marrow throughout
→ high on T1
Any residual red marrow has a high fat content → iso to high on T1
Myelofibrosis
In myelofibrosis the bone marrow is gradually replaced by fibrous tissue which
contains few water molecules and thus returns little signal on T1 or T2
weighted sequences. It is a haematological condition and concurrent
hepatosplenomegaly is common due to the need for extramedullary
haematopoiesis. Paraspinal soft tissue masses may also be seen for the
same reason. On x-rays or CT there can be a generalised increase in bone
density and it is one of the causes of a superscan on nuclear medicine bone
scans.
Marrow reconversion
Image © Medical Exam Prep
As children age, the red marrow with which we are born slowly converts to
yellow marrow, beginning in the diaphysis and spreading to either end of the
bones. By late adolescence this process is almost complete and only a few
areas of the skeleton retain red marrow, these include the proximal femora
and humeri as well as the flat bones. A small amount of red marrow does
persist throughout adulthood but various conditions can cause a reconversion whereby red marrow once again replaces the yellow marrow. On
MRI yellow marrow, which is high in fat content, returns high signal on T1 and
intermediate signal on T2. The red marrow that we are born with is isointense
to skeletal muscle on all sequences but as we age the fat content of red
marrow increases and so the appearance changes. Residual red marrow
islands can often be found close to the growth plates. It is best appreciated on
fat saturated sequences as it will experience less signal drop out than the
yellow marrow.
When haematopoiesis increases the yellow marrow can reconvert back to red
marrow. This can occur in a number of different scenarios:
Marrow reconversion
Sickle cell disease
Chronic haemolytic
anaemia
Thalassaemia
Athletes
Increased oxygen
demand or decreased High altitudes
oxygen supply
Smoking
G-CSF
Iatrogenic
Erythropoietin
On an MRI scan where you should find high T1 signal fatty yellow marrow
there will be low T1 signal red marrow which remains reasonably bright on
STIR or other fat saturated sequences. The pattern of marrow reconversion is
the exact reverse of the initial conversion, so beginning at the ends of the long
bones and spreading to the diaphysis.
In the spine in particular, it can be difficult to differentiate between marrow
reconversion and metastases. Even red marrow does contain some fat cells
and thus should exhibit some signal drop-out on STIR or out of phase images
whereas metastatic disease will not lose any signal at all.
Vertebral haemangioma
These lesions are extremely common and should be very familiar to all
candidates. They can occur anywhere but commonly arise in the vertebrae.
They have a typical appearance of vertical trabeculae which give a ‘corduroy’
appearance when viewed in sagittal or coronal planes but a honeycomb or
polka-dot appearance when viewed in the axial plane. On MRI they return
high signal on both T1 and T2 sequences.
Lymphoma
Primary lymphoma of the bone is far rarer than other types of non-Hodgkin
lymphoma but has a variety of imaging features. Most commonly on x-ray
there will be permeative bony destruction which can be overlooked initially.
Lytic lesions with a wide zone of transition may be present but patients can
also have sclerotic lesions (an ivory vertebra) or a mixed picture instead.
Cortical destruction occurs late on in the disease process. On MRI the
affected bone marrow will return low signal on T1 and high signal on T2. (by
contrast, normal bone marrow which is high in fat returns high signal on T1
and intermediate signal on T2).
Differential diagnosis for
permeative bone destruction
Lymphoma
Ewing sarcoma
Eosinophilic granuloma
Osteomyelitis
Histiocytosis (Langerhans cell histiocytosis - LCH)
There are three separate forms of this disease:
1.
2.
3.
Eosinophilic granuloma (70%) – a limited version confined to the skeleton in children or young adults. Clinically
presents as fever, raised WCC and ESR with painful bony lesions. In the skull these have a typical ‘beveled edge’
or ‘hole within a hole’ appearance or can be seen as a ‘button sequestrum’. In the spine it is one of the main
causes of vertebra plana.
Hand-Schüller-Christian Disease (20%) – classically a triad of destructive bony lesions, diabetes insipidus and
exophthalmos. In a quarter of these patients the lungs are involved with cyst formation and spontaneous
pneumothoraces possible. Nodule formation, fibrosis and honeycombing are also seen.
Letterer-Siwe Disease (10%) – a fulminant multi-organ variant affecting very young infants.
There is a strong association with smoking for patients who develop pulmonary features of LCH. Heavy smoking
causes an accumulation of Langerhans cells and hence, as with other inspiration-related lung diseases, there is a
predilection for the upper zones. The Langerhans cells can collect with other cells and become small granulomas
seen as small lung nodules. Despite being a type of fibrotic lung disease the lung volumes can be increased.
Small lung cysts form and there is a risk of spontaneous pneumothorax. There is usually sparing of the
costophrenic angles which can be a key finding.
Giant Cell Tumour also known as osteoclastoma
These are benign bony tumours arising from within bone. They can cause bony expansion from within but not
bony scalloping from without. Since they always occur in the mature skeleton they are seldom found in children
or adolescent patients although the peak age group is still young; 30s. Typically they occur around the knee but
can be found anywhere in the skeleton. They are seen on x-ray as expansile lytic lesions with the words ‘soap
bubble’ often used to describe them in literature. On MRI they usually return low signal on both T1 and T2, in
contrast to many of the potential differential diagnoses which would otherwise return high signal on one or the
other.
Haemophilic arthropathy
The larger joints are most at risk for this disease, and the knee is particularly classical. On an x-ray there may
only be a joint effusion in early disease but erosions and subchondral cysts develop. In particular there may be
widening of the intercondylar notch (for which there is a differential diagnosis of: JIA/RA, Psoriatic arthropathy,
TB and haemophilia) due to pannus formation. Also classical is epiphyseal overgrowth secondary to
hyperaemia. On an MRI there may well be nodular deposits on the synovium however the presence of blood
degradation products renders these very low in signal on all sequences with blooming artefact present on
gradient echo sequences or similar. If a haemarthrosis is present, the signal of the fluid will change depending on
the chronicity of the event.
A haemophilic pseudotumour occurs in around 1-2% of patients with haemophilia. The presence of blood
degradation products leads to a wide variety of intralesional signal patterns. The lesions are usually surrounded
by a low signal haemosiderin rim though. Lesions can arise within bone (intra-osseous) or in soft tissues (usually
muscular). Growth and pressure effects on adjacent bone can cause scalloping.
PVNS - Pigmented villonodular synovitis
The classic joint to be affected by PVNS is the knee but it can also occur at other large joints. Usually only one
joint is affected in each patient. On x-ray the only sign may be a joint effusion. Large subchondral cysts can also
be seen. On MRI however, the appearances are characteristic. Haemorrhagic proliferation of the synovium in a
frond-like fashion gives rise to the classic low signal 'feathery' sea-anemone-like finding. On susceptibility
weighted sequences there is blooming artefact owing to the presence of haemosiderin. Patients are usually
middle-aged and treatment is with synovectomy although there is a high rate of recurrence. If the patient is
male, the usual differential diagnosis for PVNS is of haemophilic arthropathy owing to the presence of blood
products there too. PVNS appears as a differential diagnosis for subarticular lucent bone lesions due to the
formation of large subchondral cysts.
Lipoma arborescens
This condition can affect children or adults and is thought to be a reaction to chronic inflammation of the
synovium leading to extensive fatty infiltration of the synovium. It is almost always the knee which is affected.
Plain radiographs will show only an effusion, which may be large, but on MRI there is frond-like or nodular
synovial proliferation which returns fat-signal according to the different sequences used. The signal should be
high on T1 and T2 but suppress on fat-saturated sequences. Post-contrast the synovium itself will enhance.
Treatment is by synovectomy.
SAPHO (Synovitis, acne, palmoplantar pustulosis, hyperostosis, osteitis)
This disease is thought to be a variant of psoriatic arthropathy. The cutaneous manifestations may not be
apparent at diagnosis (like psoriatic arthropathy) but hyperostosis and osteolysis and ankylosis of the
sternocleidomastoid joint is absolutely typical. On a nuclear medicine bone scan, bilateral uptake in the
sternoclavicular joints and manubrium is called a ‘bull’s head’ sign. About a third of patients also have spinal
disease with paravertebral ossifications and osteosclerosis. Unilateral sacroiliitis may also occur. Appearances
can be quite striking on CT. In the knees, ankles and small joints of the hands there may be inflammation of the
joints with juxta-articular osteoporosis.
Osteosarcoma
These are bone forming tumours which can either be primary, or secondary. Primary osteosarcomas occur in
young patients or young adults when the bones are more active during adolescence than in later life, and have a
predilection for either the proximal tibia or distal femur i.e. around the knee joint. Secondary osteosarcomas
occur as malignant degeneration of pre-existing bone lesions. Clinically they present as a painful mass with a
fever. Pain on movement is also typical. In later disease patients may have a raised serum ALP. On x-ray they are
poorly defined aggressive lesions with sunburst periosteal reaction and fluffy cloud-like osseous matrix. For
staging the patient should receive an MRI of the entire of the affected bone (to rule out synchronous lesions), a
nuclear medicine bone scan and a CT chest. Tissue biopsy should only be performed at tertiary referral centres
where to mitigate the risk of seeding the biopsy tract, immediate tissue analysis with the option of immediate
amputation can be performed.
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Secondary osteosarcomas:
Paget disease
Bone infarct
Osteochondroma
Osteoblastoma
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Radiotherapy change
In the case of a parosteal osteosarcoma, the attachment to the underlying bone may be thin and stalk-like but
will be present. Depending on the view a radiolucent plane may seem present for some of the length of the
tumour, giving rise to ‘string sign’ appearance, but an attachment to the parent bone will be present.
Malignant fibrous histiocytoma (MFH)
A soft-tissue MFH is the most common subtype of MFHs and the most common malignant primary soft tissue
tumour in the over 50s age bracket. It usually presents as a painless soft tissue mass which enlarges over a
matter of months. They can be large at the time of diagnosis measuring tens of centimetres. On x-ray they
appear as a partly calcified soft tissue mass. Cortical erosion of the underlying bone is an important diagnostic
feature. On MRI it returns high signal on both T1 and T2 weighted sequences.
Myositis ossificans
Trauma to the muscle causes local haemorrhage and necrosis of damaged muscle. The sequelae of this is
calcification which can persist long-term. Large muscles are particularly prone to this and the typical patient is a
young, active adolescent. Myositis ossificans appears as a calcified soft tissue mass underlying the area of
clinical concern. A periosteal reaction may or may not be present but crucially there is no erosion of the
underlying cortex, a fact which discriminates it from malignant fibrous histiocytoma. The string sign refers to
the presence of a plane of normal tissue separating the mass from the bone and unlike a parosteal
osteosarcoma, in myositis ossificans this plane will extend along the whole length of the mass completely
separating it from the bone.
Tumoral calcinosis
Surprisingly for the sometimes extreme appearance of this condition, it can be completely painless. Patients are
typically black and in their teens or 20s. Around a third of cases are inherited in an autosomal dominant fashion.
A biochemical defect in the metabolism of phosphorus leads to accumulation of hydroxyapatite fluid around the
joints causing a foreign-body type granulomatous reaction and fibrous capsule development. On imaging this
appears as a progressive and calcified soft tissue mass. The skin overlying the mass can ulcerate and exude a
chalky or milk like fluid. Any or all of the hips, shoulders and elbows can be affected but characteristically
tumoral calcinosis does not affect the knees. Importantly the underlying bones are normal, a feature which
differentiates it from gout or pseudogout.
Gout
Excess circulating urate levels leads to crystalisation of urate (monosodium urate crystals) within the joint
spaces. An acute attack may be precipitated by any acute event such as trauma or surgery as well as a change in
diet to include purine containing foods (liver, kidney, game meat, some seafood, alcohol). Historically chronic
manifestations of this condition included the development of gouty tophi; white lumpy areas under the skin
which could ulcerate and exude a chalky material. These are still seen today but far less so thanks to improved
management strategies. Involvement of the first metatarsophalangeal joint is considered classical but
involvement of the carpometacarpal joints of the hands is often most debilitating where it occurs. On x-ray the
earliest radiological manifestation is a joint effusion. Joint erosions develop on the lateral corners of a joint but
contrary to many other erosive processes the base of the ulcers has a sclerotic margin. Juxta-articular
osteopenia is not often seen, a feature which acts as a good distinguisher from rheumatoid arthritis, which is
thought to be because the attacks come in acute bursts during which time disuse osteopenia does not have the
time to develop. Another reasonably specific feature of gouty arthritis is the preservation of the joint space itself
until relatively late into the disease.
Crystals
Content
Gout
Monosodium urate
Pseudogout
Calcium pyrophosphate dehydrate
Shape
Needle
Rhomboid
Birefringence
Strongly negative
Weakly positive
Osteosarcoma
Secondary osteosarcomas
Paget disease
Bone infarct
Osteochondroma
Osteoblastoma
Radiotherapy change
These are bone forming tumours which can either be primary, or secondary. Primary osteosarcomas occur in
young patients or young adults when the bones are more active during adolescence than in later life, and have a
predilection for either the proximal tibia or distal femur i.e. around the knee joint. Secondary osteosarcomas
occur as malignant degeneration of pre-existing bone lesions. Clinically they present as a painful mass with a
fever. Pain on movement is also typical. In later disease patients may have a raised serum ALP. On x-ray they are
poorly defined aggressive lesions with sunburst periosteal reaction and fluffy cloud-like osseous matrix. For
staging the patient should receive an MRI of the entire of the affected bone (to rule out synchronous lesions), a
nuclear medicine bone scan and a CT chest. Tissue biopsy should only be performed at tertiary referral centres
where to mitigate the risk of seeding the biopsy tract, immediate tissue analysis with the option of immediate
amputation can be performed.
In the case of a parosteal osteosarcoma, the attachment to the underlying bone may be thin and stalk-like but
will be present. Depending on the view a radiolucent plane may seem present for some of the length of the
tumour, giving rise to ‘string sign’ appearance, but an attachment to the parent bone will be present.
Some of the pertinent subtypes of osteosarcoma
Lower grade, older age (20-50s)
Parosteal
Telangiectatic
Purely lytic, poor prognosis, fluid-fluid levels
Multicentric
Ages 5-10 with very poor prognosis
Eggshell calcification
When the outer rim of a lymph node becomes calcified it is seen on CT as eggshell calcification. There is a
relatively specific differential diagnosis for diseases which can manifest in this way.
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Fibrosing mediastinitis
Amyloidosis
Pneumoconioses - silicosis and coal workers only. Not seen in most others.
Sarcoidosis
Scleroderma
Treated lymphoma (ie post radiotherapy)
TB
Histoplasmosis
Involvement of either the upper or lower zones is typical for a number of different pathologies. Many of the
upper lobe pathologies related to inhalational processes and conversely many of the lower lobe pathologies can
be explained by their basis in the increased blood flow. There are a number of different mnemonics for either
area, some better than others.
For example, a mnemonic for involvement of the upper zones is BREASTS:
B = Beryllosis
R = Radiation
E = Eosinophilic granuloma (Langerhans cell histiocytosis) and Extrinsic Allergic Alveolitis
A = Ankylosing spondylitis
S = Sarcoidosis
T = Tuberculosis
S = Silicosis
Involvement of the lower zones can be remembered with the mnemonic BADAS:
B = Bronchiectasis
A = Aspiration pneumonia
D = Drugs and Desquamative interstitial pneumonia
A = Asbestosis
S = Scleroderma (and Rheumatoid arthritis)
The reverse halo appearance is synonymous with COP (also known as BOOP – Bronchiolitis obliterans
organizing pneumonia). It is seen as central ground glass opacification surrounded by a ring of consolidation.
There are other conditions which can cause this appearance, of which the prominent ones are:



Wegener granulomatosis
Sarcoidosis
Pneumocystis carinii pneumonia
The halo sign is seen when there is a central nodule surrounded by ground glass opacification. It is almost as
synonymous with invasive aspergillosis but is also seen in:







Other fungal infections
Septic emboli
TB
Hemorrhagic metastasis
Minimally invasive adenocarcinoma of the lung (Bronchioalveolar carcinoma)
Hypersensitivity pneumonitis
Wegeners granulomatosis
The azygo-oesophageal recess is formed by the interface of the right lung and the mediastinal reflection of the
azygos vein.
The anterior junctional line is formed by the meeting of the parietal and visceral pleura anteromedially.
The posterior junctional line is formed by the meeting of the pleural surfaces of the upper lobes behind the
oesophagus.
The right paratracheal line is formed by the right wall of the trachea against the right lung.
The right paraspinal stripe is formed by the meeting of the right lung against the posterior mediastinal soft
tissue.
Crazy paving
This is the term given to the appearance of interlobular septal thickening on a background of patchy ground
glass opacification (GGO). In an exam question setting it is strongly indicative of alveolar proteinosis simply
because most patients with alveolar proteinosis do have a crazy paving pattern but crazy paving does does occur
in a variety of other conditions:





Alveolar proteinosis
Acute respiratory distress syndrome
Goodpasture syndrome
Cryptogenic organising pneumonia (COP)
Sarcoidosis
Alveolar proteinosis
Overproduction of surfactant and/or reduced efficiency of clearance mechanisms result in accumulation of
proteinaceous surfactant in the air spaces. It is a rare condition of young or middle aged adults and there is a
strong association with smoking. The classic description for the CT signs seen with alveolar proteinosis is a crazy
paving pattern. This is caused by the combination of interlobular septal thickening and patchy ground glass
opacification. This is seen in a perihilar (also known as batwing) distribution. Of note there is no association with
lymph node enlargement or effusions.
Goodpasture syndrome
This is an autoimmune disease caused by anti-glomerular basement membrane antibodies. The alveolar
membrane also falls victim to circulating auto-antibodies. Patients present as adolescents or young adults with
glomerulonephritis and haemoptysis. Bilateral consolidation changes can be seen on imaging which
characteristically become reticular over the ensuing few weeks. This is due to organisation of the pulmonary
haemorrhage and can appear as a crazy paving pattern.
Idiopathic pulmonary haemosiderosis
Pulmonary haemosideration refers to the deposition of iron within the lungs. This can be secondary to a cause of
lung haemorrhage such as Goodpasture syndrome or can be idiopathic. There is symmetrical involvement of the
lower zones with a progression to a nodular/linear pattern.
Sarcoidosis
‘The great mimic’. In the real world sarcoidosis can appear as almost anything, almost anywhere. Despite this,
there are usual ways for sarcoidosis to appear and these are more likely to be tested in exam questions. The
classic patient for pulmonary sarcoidosis is young, female and black with hypercalcaemia. Raised ACE
(Angiotensin-converting enzyme) levels should make you think of sarcoidosis, as should a positive KveimSiltzbach test (an intracutaneous injection of a suspension of human sarcoid spleen or lymph nodes). Nine out of
ten patients with sarcoidosis will have some of thoracic manifestation. Bilateral hilar lymphadenopathy is
typical. There are many features considered classical for sarcoidosis:





The ‘1, 2, 3’ sign is present in at least three quarters of patients. It is also called the Garland triad or the
pawnbroker's sign and refers to a specific pattern of lymph node enlargement involving both hilar nodes as well
as the right paratracheal nodes.
Egg-shell calcification of lymph nodes - this is not exclusive to sarcoidosis but is seen in increasing numbers of
patients as the disease duration increases
Traction bronchiectasis.
Upper lobe predominance.
Nodules - these are usually in a perilymphatic distribution but are also found elsewhere. Cavitation can occur but
is not typical.
Please note that the question asks for the LEAST likely option.
ARDS is a severe life threatening entity that accelerates rapidly. Patients
develop rapidly progressive dyspnoea, tachypnoea and hypoxia. As the
alveoli fill with fluid and debris an arteriovenous (right-to-left) shunt develops
since although the lungs may be well perfused, the under-aeration of the
alveoli prevents gas exchange. Despite oxygenation therefore, the hypoxia
becomes refractory to oxygen therapy as oxygenation can only improve a
situation where the patient is ventilating adequately.
Causes of ARDS (Mnemonic - DICTIONARIES)
• DIC
• Infection
• Caught drowning
• Trauma
• Inhalants (smoke, NO2)
• Oxygen toxicity
•
•
•
•
•
•
Narcotics / drugs
Aspiration
Radiation
Includes pancreatitis
Emboli (fat, fluid)
Shock (septic, cardiogenic, anaphylactic, haemorrhagic)
The chest x-ray may be normal initially but descends into patchy opacification
and which becomes confluent and extensive within hours, involving most if not
all of both hemithoraces. On a CT scan there is usually extensive ground
glass opacification and dependant consolidation. The presence of nondependant consolidation should raise the possibility of superadded infection at
any stage of the course of the disease.
Image 1: Patchy opacification
Image sourced from Wikipedia
(link is external)
Courtesy of Samir CC BY-SA 3.0
(link is external)
Image 2: Confluent opacification
Image sourced from Wikipedia
(link is external)
Courtesy of Altaf Gauhar Haji, Shekhar Sharma, DK Vijaykumar and Jerry
Paul CC BY-SA 2.0
(link is external)
Time
Lung pathology
Microemboli of fibrin and
platelets
First 12 hours
12-24 hours
Interstitial oedema
Interstitial and alveolar
oedema,
microatelectasis
Hyaline membrane
formation, hyperplasia of
type 2 pneumocytes
Collagen deposition and
fibrosis, often with
superadded infection
24-48 hours
5-7 days
7-14 days
Radiological findings
During this time there may be no radiological findings
Air space opacities
Dependant consolidation
Air space opacities
Dependant consolidation
Reticular opacities and decreasing consolidation
Non dependant consolidation (suggesting infection)
Subpleural reticulation and honeycombing (sequelae of developing fibrosis)
The changes within a lung can be charted according to a timeline:
If patients do survive they are initially often left with fibrotic changes in the
lungs but many patients actually experience surprisingly few long-term
sequelae. The lungs gradually remodel and resolve the fibrotic changes that
take place in the intermediate term.
The wedge capillary pressure is measured via a Swan-Ganz catheter inserted
peripherally and fed through the right side of the heart to reach a branch of
the (usually left) pulmonary artery. A small balloon can be inflated to
temporarily occlude this artery and a tiny transducer at the tip of the catheter
measures the pressure as the balloon deflates (the mechanism is similar to
blood pressure recording via an upper arm cuff).
Wedge capillary pressure is a surrogate measure for left atrial pressures
which rise with left ventricular failure or problems with the aortic and mitral
valves. If the capillary wedge pressure is elevated then a cardiac cause
should be strongly suspected. Non-cardiogenic causes of ARDS should not
elevate the capillary wedge pressure.
Please note that the question asks which finding is NOT likely to be found.
Talcosis causes hypERdense nodules, not hypOdense nodules.
There are a number of ways in which recreational drug use can affect the patient and be seen radiologically.







Talcosis - embolisation of particulate matter injected intravenously gives rise to centrilobular micronodules
which may be high density.
Septic emboli - secondary to non-sterile intravenous injection and endocardial vegetations. Cavitating lung
nodules associated with clinical manifestations of infection.
Apical bullae/pneumothorax - associated with inhalational drugs, cannabis, cocaine, ecstasy, amphetamines
Pulmonary oedema - Perihilar airspace opacification with or without pleural effusions. Associated with cocaine,
heroin, methamphetamine use.
Consolidation - straightforward lower respiratory tract infection secondary to atypical lifestyle, concurrent
immunosuppression, or aspiration during periods of reduced consciousness.
Nasal septum destruction - associated with snorting cocaine, due to vasoconstriction and necrosis.
Skin abscesses and pseudoaneurysm - formation at injection sites
The ribs are narrow, curved, flat bones that form most of the thoracic cage.
The true ribs are the first seven ribs (sometimes eight). They are called the true ribs because they attach the
vertebrae to the sternum through their costal cartilages.
The false ribs are the 8th to the 10th ribs (the vertebrochondral ribs). They are called the false ribs because their
cartilages are joined to the cartilage of the rib just superior to them.
The floating ribs are the 11th and 12th ribs. They are called the false ribs because their cartilages end in the
posterior abdominal musculature.
Alpha 1 antitrypsin deficiency
Alpha-1 antitrypsin is a glycoprotein which is made in the liver and secreted. One of its functions in the lungs is
to oppose the action of proteolytic enzymes the likes of which are secreted by white blood cells in order to
counter sub-clinical bacterial infections. Since A1AT is deficient in these patients the unopposed action of the
enzymes goes beyond the intended destruction of pathogenic bacteria and causes damage to the lung tissue.
Patients are usually diagnosed in early adulthood when their symptoms develop. On CT there is panacinar
emphysema, particularly affecting the bases. Bronchiectasis is also often seen. Cirrhosis is another feature of
this disease and should be looked for on imaging.
Lymphangioleiomyomatosis (LAM)
LAM can go misdiagnosed for many years as emphysema. It occurs exclusively in non-smoking women of
childbearing age and quite often a history of spontaneous pneumothorax is given. Radiologically there are
numerous small cystic spaces surrounded by normal lung. A chylous pleural effusion (negative Hounsfield units)
is reasonably specific. The main differential diagnosis would be histiocytosis which tends to be associated with
smoking, classically spares the costophrenic angles and gives small nodules but both can present with
spontaneous pneumothorax and give small cysts. The lung volumes in LAM will remain normal whereas they can
be increased in Histiocytosis (surprisingly for a fibrotic lung disease).
Congenital lobar overinflation (previously congenital lobar emphysema)
This condition is thought to be caused by underdevelopment of bronchial cartilage in the affected lobe(s).
Consequently the bronchus is unable to remain patent during expiration leading to significant air trapping. It is
usually the left upper lobe which is affected but approximately 40% of cases involve the left upper lobe; the right
middle or the right upper lobes are affected in a further 55% of cases. There is a reasonable male preponderance
of approximately 3:1.
On a CXR there is hyperlucency of the affected lobe and often mass effect on the mediastinum leading to
contralateral mediastinal shift and thereby respiratory distress.
Swyer-James syndrome
In this condition, normal development of the infant lung is impeded by bronchiolitis (viral or mycoplasma) at an
early age, with superadded acute airspace destruction. Consequently the affected lobe is small and lucent on the
CXR due to air trapping. It is a differential diagnosis for a unilateral lucent hemithorax, along with a
pneumothorax, very large pulmonary emboli and causes of decreased chest wall musculature such as Poland
syndrome or, historically, polio. In an an exam situation Swyer-James syndrome is usually given as a teenage or
young adult patient with a history of recurrent LRTIs. Air trapping, and bronchiectasis can also be described.
Neurofibromatosis
Technically neurofibromatosis (type I) is included in the differential diagnosis for lung cysts (particularly in the
upper lobes) however the rest of the information provided is insufficient to make this the most likely answer
here.
Pleural disease is common in rheumatoid lung disease but not a diagnosis of exclusion. Alternatively, patients
can develop diffuse interstitial fibrosis with medium or coarse reticulations affecting the lower lobes
predominantly.
Of the other options given:
Ground glass opacification with a mosaic pattern on expiration and an upper lobe predominance suggests
extrinsic allergic alveolitis (EAA).
Subpleural well defined small nodules in an upper zone predominance with bilateral hilar lymph node
enlargement suggests sarcoidosis.
Peripheral interstitial changes with traction bronchiectasis and paraseptal emphysematous changes in the upper
zones suggests ankylosing spondylitis.
Patchy ground glass opacification with traction bronchiectasis and calcified lymph nodes suggests silicosis.
ABPA causes a ‘migratory pneumonitis’, typically affecting the upper lobes. Parenchymal changes are fleeting;
appearing in one area of the lung one week and a different area the next. The ‘finger in glove’ sign can often be
seen, where mucus plugging of a bronchus allows the distal airway to fill with secretions giving rise to a ‘V’ or Y’
shaped shadow on a CXR or CT. This is known as a finger in glove sign owing to its appearance. Central
bronchiectasis is a prominent feature and is can be given in an exam question setting as ‘ring shadows’ on a CXR.
The peripheral bronchi are classically spared. Cavity formation is seen in the later stages of the disease although
aspergillomas are not typical (these occur in patients with a normal immune system). The typical patient in an
exam question setting will be young, with a history of either asthma or cystic fibrosis or ‘chronic lung disease’,
symptoms of malaise, headache and intermittent chest pains, and an eosinophilia on their full blood count.
The differential diagnosis for the gloved finger sign includes:





ABPA
Cystic fibrosis
Bronchogenic carcinoma
Congenital lobar overinflation
Bronchial atresia
Hamartoma
Fat within a thoracic mass is diagnostic of a hamartoma but is only seen in approximately half of cases.
Hamartomas form part of Carney triad (pulmonary hamartomas, gastric leiomyosarcomas and extra-adrenal
paragangliomas). NB this is different from Carney syndrome (atrial myxoma, facial/buccal pigmentation, sertoli
tumours of the testis and multiple other findings).
The differential diagnosis for cavitating lesions is unusually memorable (CAVITY):
C = Cancer (Squamous cell carcinoma – either bronchogenic or metastatic, or adenocarcinoma)
A = Autoimmune granulomas (Wegener granulomatosis and Rheumatoid arthritis granulomas)
V = Vascular (septic emboli)
I = Infection (abscess, TB or cavitating pneumonias [strep, staph, aspergillus, legionella, klebsiella])
T = Trauma – pneumatocoeles
Y = Youth (ie congenital – CPAM, sequestration, bronchogenic cyst) These all form cysts, not true cavities as
such.
Lymphangioleiomyomatosis (LAM) is associated with mediastinal lymph node enlargement but is not a
usual differential diagnosis for bilateral hilar lymph node enlargement. The main differential diagnoses
would be:

Malignancy
o
o

Lymphoma (Hodgkin > non-Hodgkin)
Carcinoma
Infection
o
o
o



Tuberculosis
Histoplasmosis
Mycoplasma
Silicosis
Sarcoidosis
Lymphangioleiomyomatosis (LAM)
LAM can go misdiagnosed for many years as emphysema. It occurs exclusively in non-smoking women
of childbearing age, unlike this patient, and quite often a history of spontaneous pneumothorax is given.
Radiologically there are numerous small cystic spaces surrounded by normal lung. A chylous pleural
effusion (negative Hounsfield units) is reasonably specific. The main differential diagnosis would be
histiocytosis which tends to be associated with smoking, classically spares the costophrenic angles and
gives small nodules but both can present with spontaneous pneumothorax and give small cysts. The
lung volumes in LAM will remain normal whereas they can be increased in Histiocytosis (surprisingly for
a fibrotic lung disease).
As an overall strategy, the most important stages to understand are those which change the
management for patients. The patient in this scenario is stage IIIa and thus potentially curable with an
aggressive management plan. At Stage IIIb the management changes significantly because stage IIIb
and stage IV patients are unresectable. Other facts relating to lung cancer (TNM staging) that are useful
to know are those regarding satellite nodules:
o
o
o
Same lobe = T3
Different lobe = T4
Contralateral lung = M1
Post-operative radiotherapy should be offered to the following patient groups:



Patients with N2 level nodes
Patients with positive resection margins
These patients should be WHO performance status 0 or 1 and should also have ‘satisfactory’ preoperative lung function tests
Post-operative chemotherapy should be offered to:



T1-3
N1-2
(Stage II/III)
For lung cancer some of the important staging features are as follows:




T1 tumours are <3cm
N1 = ipsilateral hilar nodes
T2 tumours are >3cm but >2cm from the carina
N2 = ipsilateral mediastinal or subcarinal nodes
T3 tumours are any size with extension to:
N3 = contralateral hilar, mediastinal or
supraclavicular nodes
Chest wall
Pleura or pericardium
<2cm of the carina
Satellite nodules within the same lobe
M1 = bilateral lesions, malignant pleural effusion,
distant metastases
T4 tumours affect diaphragm, mediastinal organs,
carina, vertebral body
T1 and T2 both have further subdivisions.
Unresectable tumours are T4, N3 or M1.
Beyond TNM staging patients with similar prognostic outcomes are given further stages. Simple
observation of these groupings reveals the following:



Stage I patients MUST be N0
Stage III patients MUST have a sum ≥ 3 (ie T2N2M0, or T1N2M0). [NB some patients with Stage II will
also have a sum of 3 (for example T2N1M0) however ALL stage III patients have a sum ≥ 3.]
Stage IIIb patients are unresectable → stage IIIb is denoted either by N3 status or T4N2.
The management of the less common small cell lung cancer is slightly different; the tumours are usually
much more aggressive, with earlier metastasis and poorer long term survival statistics. The primary
lesion may not be seen separately to the resultant associated nodal mas.
Neurofibroma
Dumbbell protrusion of a spinal mass through the neural foramina is a classic description for a
neurofibroma. The slow growth of this lesion means there is bony remodeling around it rather than
invasion. Neurogenic tumours are the most common cause of a posterior mediastinal mass.




A bronchogenic carcinoma – this would be more likely to invade bone as opposed to remodel it
Lymphoma – this is unlikely to be as isolated a finding as a solitary 3cm mass
Extramedullary haematopoiesis – this would usually also be expected to be multi-level
Marfan syndrome – this is associated with dural ectasia which can in turn also be seen in
neurofibromatosis. Dural ectasia causes posterior vertebral body scalloping though, not unilateral
dumbbell expansion of the foramina.
Other possible posterior mediastinal masses would be:




Thoracic aortic aneurysm
Ewing sarcoma – aggressive
Lymphoma – multi-level
Paraspinal abscess – unlikely to cause bony remodeling
The main cavitating neoplastic culprits are:
o
o
o







Bronchogenic carcinoma (Squamous cell carcinoma)
Metastatic squamous cell carcinoma
Adenocarcinoma (Colon + breast)
Contrast enhancement in a nodule is a strong indicated of malignancy and vice versa is also true; the
absence of contrast enhancement strongly suggests a nodule is benign. True dependancy (on both
supine and prone scans) would be suggestive of aspergilloma formation. Volume loss suggests fibrosis.
Atelectasis has many causes and is more often seen in benign disease than as a consequence of
neoplasia. Bronchiectasis implies chronicity and is not linked to malignancy (with the exception of postradiotherapy change).
Certain Cancers Spread By Plugging The Lymphatics (this is not an exclusive list). Of these Breast
accounts for just over half of cases and gastric cancer accounts for most of the remainder.
Cervix
Colon
Stomach
Breast
Pancreas
Thyroid
Larynx (or lung – bronchogenic)
Oesophageal leiomyoma
Leiomyomas are said to be the only oesophageal lesions which can calcify. Generally, the absence of
any shouldering of a stricture is a benign feature. Leiomyomas tend to arise in relatively young patients
and are more common in the mid or distal thirds of the oesophagus. Ulceration is a very uncommon
feature.
Oesophageal carcinoma
Squamous cell carcinoma (SCC) of the oesophagus predominantly affects the middle and lower thirds
of the oesophagus and accounts for around 60% of oesophageal malignancies. Adenocarcinoma arises
in the lower third, mostly in areas of Barrett oesophagus, and accounts for most of the remaining 40%.
Both histological types are more commonly found in the lower part of the oesophagus than the upper
part, but that being said, if a cancer is found in the upper third of the oesophagus, it is most likely to be
squamous cell in origin. Some patients develop symptoms of dysphagia and retrosternal pain but sadly
many tumours remain occult until they are at an advanced stage. This is in-part due to the fact that there
is no serosal layer protecting the oesophagus and as such cancers can progress rapidly. Patients found
to have Barrett oesophagus (metaplasia of the usual squamous epithelium to columnar epithelium) are
screened frequently for adenocarcinoma. Importantly in the staging criteria, the only nodes which
contribute to nodal staging are the immediately local ones to the cancer. Any involved lymph nodes of
the cervical chains or coeliac region are considered as metastatic disease. It is therefore important to
review these areas on a staging scan with particular attention.
Achalasia
This is a motility disorder which causes a failure of relaxation of the gastro-oesophageal junction (GOJ)
and disorganisation of oesophageal peristalsis. Ingested material (including barium during fluoroscopy)
is held up at the GOJ in a column. On a barium study the column has a classical bird-beak tapering
point at the inferior-most end where it reaches the GOJ. There is often then sudden emptying of the
oesophagus due to eventual pressure on the GOJ exceeding its strength. Oesophageal contractions
may be absent or may be non-peristaltic. On a CXR an air-fluid level may be seen behind the heart.
Aberrant right subclavian artery
This common anomaly occurs when instead of being the first major branch of the aorta (technically the
first branches are the coronary arteries), the right subclavian artery arises distal to the left subclavian
artery. It then has to swerve back around to reach the right side and in doing so usually runs posterior to
the oesophagus, which can be seen on a barium study as a smooth indentation. In some cases it can
exert sufficient pressure on the oesophagus to cause dysphagia which is termed dysphagia lusoria.
An aberrant left pulmonary artery is the ‘only’ vascular anomaly to run between the oesophagus and the
trachea. There are cases of aberrancy of the right pulmonary artery in the literature however these
patients tend to die in infancy.
An anterior indentation of the oesophagus is caused by:

An aberrant left pulmonary artery
A posterior indentation of the oesophagus is caused by:



A right sided arch with an aberrant left subclavian artery
A left sided arch with an aberrant right sided subclavian artery
A double aortic arch – this is usually described as also causing an anterior indentation to the
trachea
Pancreatic Islet cell tumours
Insulinomas account for almost half of these with gastrinomas making up most of the remainder.
Glucagonomas are the next most common after that. When the tumours are functioning, i.e. Producing
the hormones after which they are names, then they present at a relatively small size with patients
reporting symptoms pertaining to the respective hormones. Non-functioning tumours are far larger when
they present. Islet cell tumours show striking arterial enhancement on CT and when they metastasize,
often to the liver, the metastases show similar arterial enhancement. They may be of low reflectivity with
a bright hyperechoic rim if seen in ultrasound but ultrasound is a poor modality for imaging the upstream
pancreas. On MRI the tumours return low signal on T1 and high signal on T2 with strong arterial
contrast enhancement.
The classic clinical picture with glucagonomas can be summarised as the 4 Ds namely, Diabetes, Deep
vein thrombosis, Depression and Dermatitis although this is relatively rare. Most patients develop an
unfortunate condition called necrolytic erythema migrans which is an intensely itchy maculopapular
rash. Although less common than insulinomas and gastrinomas, glucagonomas are associated with
MEN as well.
VIPomas cause a watery diarrhoea and hypokalaemia termed Verner-Morrison syndrome. They are not
associated with MEN.
Multiple Endocrine Neoplasia (MEN)
There are three types of MEN and all are inherited in an autosomal dominant fashion. Defects in tumour
suppression genes on either chromosomes 10 or 11 allow the development of multiple neoplastic
lesions affecting multiple endocrine organs. The syndromes overlap making them challenging to
distinguish but they are separate entities and lend themselves well to MCQs. Interestingly where
parathyroid hyperplasia is present in 97% of patients with MEN 1, medullary carcinoma of the thyroid is
present in just shy of 100% of MEN 2A.
Syndrome
Aide
memoire
PPP
MEN 1 = Wermer
syndrome (ch11)
PaMPhe
MEN 2A = Sipple
syndrome (ch10)
Main features
Other features
Parathyroid hyperplasia
Adrenocortical hyperplasia
Pancreatic islet cell tumour
Carcinoid
(Anterior) Pituitary gland tumours
Lipomas
Parathyroid hyperplasia
Medullary carcinoma of the thyroid
Carcinoid
Pheochromocytoma
MPheG
MEN 2B = Mucosal
neuroma syndrome
(ch10)
Medullary carcinoma of the thyroid
Phaeochromocytoma
Marfanoid appearance
Ganglioneuromatosis (mucosal
neuromas)
Choledochal cyst
Reflux of pancreatic enzymes into the common bile duct leads to weakening of the wall of the common
bile duct [CBD] (+/- the common hepatic duct) and thereafter aneurysmal dilatation termed a
choledochal cyst. There are five different subtypes. Patients are mostly diagnosed in childhood. If
undiagnosed to adulthood patients present with a triad of episodic jaundice, right upper quadrant pain
and a right upper quadrant mass.





Type I – This is by far the most common version. The common bile duct is affected either focally or
along its entire length.
Type II – A true diverticulum of the CBD
Type III – Focal dilatation of the CBD contained within the wall of the duodenum. This type is also called
a choledochocoele. They present slightly later with most patients being in their 30s at the time of
diagnosis and can be seen as a duodenal filling defect on barium follow-through studies.
Type IV – The intrahepatic and extrahepatic biliary ducts are affected
Type V – The intraheptic ducts are affected alone. This is termed Caroli disease however there is some
discrepancy in the literature as to whether this can be called a type V choledochal cyst or whether it is a
separate disease in its own right. Caroli disease (cavernous ectasia of the intrahepatic ducts) can be
inherited in an autosomal dominant fashion. When present it is quite striking on imaging with saccular
dilatation of most of the larger intrahepatic biliary ducts alongside focal strictures giving a beaded
appearance. There is an association with medullary sponge kidney and patients are at significantly
increased risk of developing cholangiocarcinoma.
Adrenal metastasis
Secondary adrenal malignancies are more common than primary ones and the second most common
adrenal lesion overall(after adenoma). The main four cancers to metastasize to the adrenal glands are
four of the most prolific cancers namely: breast, colon, lung and pancreas. Of the remaining cancers,
malignant melanoma can metastasize to the adrenal glands. The appearance of an adrenal metastasis
varies hugely. They can be relatively low in attenuation on CT owing to a degree of central necrosis.
Whereas adenomas tend to washout on multi-phase imaging, metastases often display far slower
washout characteristics.
Pancreatic ductal adenocarcinoma
Unfortunately pancreatic adenocarcinoma has a poor prognosis and is also reasonably common. At the
time of diagnosis only 10% have surgically resectable disease and the 5 year survival rate is pitifully low
at 2-3%. The classical specific presentation is with painless jaundice (Courvoisier sign – painless
jaundice and a right upper quadrant mass is unlikely to be caused by gallstones) however most patients
actually present with vague abdominal or right upper quadrant pains. The tumour markers usually found
are CEA and Ca19-9. Smokers, obese patients and those with a relevant oncological family history of
hormonal cancers are at increased risk of developing the cancer, as are those suffering from cancer
syndrome such as HNPCC (hereditary non polyposis colorectal cancer). On ultrasound the tumour will
show low reflectivity compared to any adjacent normal pancreatic tissue. On CT the masses tend to
enhance poorly.
The key to management is operability. Involvement of various different local structures excludes or
potentially excludes some patients from surgical management as follows:




Operable
Duodenum
Borderline operable
Veins – IVC, SMV and Portal vein
Palliative
SMA
Spleen
Arteries – aorta, splenic artery if further
Coeliac axis
than 1cm from origin,
A Meckel’s diverticulum is a vestigial remnant of the vitellointestinal duct. It is the commonest
malformation of the gastrointestinal tract, being present in around 2% of the population. They are twice
as common in men than women.
When present a Meckel’s diverticulum is located in the distal ileum, usually within 60-100 cm (2 feet)
of the ileocaecal valve. They are usually 3-6 cm (approx. 2 inches) long and may have a greater lumen
than that of the ileum.
They are commonly found as an incidental finding, particularly at appendicectomy. The majority are
asymptomaticbut they can present with the following complications:
Haemorrhage (25-50% of complications)
Intestinal obstruction (10-40% of complications)
Diverticulitis
Perforation
Meckel’s diverticula run antimesenterically but receive their blood supply from the mesentery of the
ileum, and a typical feeding vessel called the vitelline artery can be identified. They are typically lined
with ileal mucosa but frequently contain ectopic mucosa, the two commonest types being gastric (50%)
and pancreatic (5%). More rarely colonic or jejunal mucosa may be present.
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The ‘rule of 2s’ is a useful aide-mémoire
2% of the population
2:1 male: female ratio
2 feet from the ileocaecal valve
2 inches in length
2 types of common ectopic tissue (gastric and pancreatic)
2 years most common age at clinical presentation
The most specific sign of biliary atresia is the triangular cord sign. This is an echogenic band running
anterior to the portal vein at the porta. A small gallbladder, dilated intrahepatic ducts and nonvisualisation of the gallbladder are all features consistent with biliary atresia, but the triangular cord sign
would be most indicative of the condition. It is associated with polysplenia and heterotaxy syndrome.
Biliary atresia
This presents between two weeks and two months of life as an obstructive jaundice picture (i.e.
conjugated hyperbilirubinaemia). The extrahepatic bile ducts have become fibrosed and cause
obstruction. Initial investigation is usually with ultrasound and an echogenic ‘triangular cord’ structure in
the porta hepatitis is considered pathognomic. The gallbladder may be normal, small or non-visualised
and therefore contributes little to the diagnosis. Further investigation is often with a HIDA scan. If there
is normal activity within the liver (usually after only a few minutes) but there is no visualisation of tracer
within the bowel after 24 hours this is considered diagnostic. Phenobarbitol can be given in the days
leading up to the scan to increase biliary output.
Cholangiocarcinoma
Any disease which causes chronic biliary inflammation predisposes the patient to developing
cholangiocarcinoma, a malignancy of the biliary tree. In particular, inflammatory bowel disease poses a
10 times greater risk. Painless jaundice is the presenting feature in around one in ten patients but
mostly patients present more insidiously with abdominal pain or weight loss.
Cholangiocarcinomas can be intra or extrahepatic and a few of the pertinent features of each are listed
in the table below.
Extrahepatic
Intrahepatic
90% (Right > left)
10%
Fluctuating painless jaundice
Painful or painless jaundice, weight
loss
Ductal strictures
Satellite nodules
A Klatskin tumour is an intrahepatic tumour arising at the confluence of the left and right hepatic ducts
where they join to form the common hepatic duct. Consequently it obstructs both ducts separately. On
MRCP or ERCP this is seen as duct dilatation where the left and right ducts fail to communicate with
one another. The location is relevant in identifying this type of tumours since they tend to be aggressive
in nature, even for cholangiocarcinomas.
On ultrasound a cholangiocarcinoma can have a variable appearance. Duct dilatation, if present, should
be evident. On CT the tumour will be hypodense but can show early rim enhancement with contrast,
followed by filling-in leading to homogeneous delayed enhancement by around 15minutes. Thereafter
there is washout which, again, begins peripherally. Appearances therefore depend hugely on the phase
of the scan. Since cholangiocarcinomas do not derive from hepatocytes they do not take up sulphur
colloid and thus will appear cold on a sulphur colloid scan.
Primary sclerosing cholangitis (PSC)
Although benign in nature PSC can wreak havoc for patients unfortunate enough to develop it. It is twice
as common in men as in women and 70% of patients have a history of inflammatory bowel disease. Bile
duct strictures form (particularly at the bifurcation/confluence of ducts) and lead to an obstructive
jaundice picture. In between strictures there is dilatation and the combination of the two leads to a string
of beads type appearance. The appearance on ERCP or MRCP in some patients can also resemble a
tree in winter with pruning of the upstream branches. Outpouchings also form which are either true or
pseudo-diverticulae. Hepatic atrophy is present in chronic cases, although the caudate lobe is usually
spared. Patients unfortunately have a higher risk of developing cholangiocarcinoma.
Primary biliary cirrhosis (PBC)
This can be difficult to distinguish from PSC however whereas PSC can involve both intra and
extrahepatic ducts, PBC only involves the intrahepatic ducts. It is an autoimmune condition and, like
many other autoimmune conditions, patients are typically women in their middle ages. Antimitochondrial
antibodies (AMA) are present in the vast majority of patients. On imaging, the secondary cirrhotic effects
are most pertinent with caudate lobe hypertrophy and left lobar atrophy. The periportal halo sign as
seen on MRI is reasonably specific and relates to fluid accumulation around the portal triad.
Choledochal cyst
Reflux of pancreatic enzymes into the common bile duct leads to weakening of the wall of the common
bile duct [CBD] (+/- the common hepatic duct) and thereafter aneurysmal dilatation termed a
choledochal cyst. There are five different subtypes. Patients are mostly diagnosed in childhood. If
undiagnosed to adulthood patients present with a triad of episodic jaundice, right upper quadrant pain
and a right upper quadrant mass.
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Type I – This is by far the most common version. The common bile duct is affected either focally or
along its entire length.
Type II – A true diverticulum of the CBD
Type III – Focal dilatation of the CBD contained within the wall of the duodenum. This type is also called
a choledochocoele. They present slightly later with most patients being in their 30s at the time of
diagnosis and can be seen as a duodenal filling defect on barium follow-through studies.
Type IV – The intrahepatic and extrahepatic biliary ducts are affected
Type V – The intraheptic ducts are affected alone. This is termed Caroli disease however there is some
discrepancy in the literature as to whether this can be called a type V choledochal cyst or whether it is a
separate disease in its own right. Caroli disease (cavernous ectasia of the intrahepatic ducts) can be
inherited in an autosomal dominant fashion. When present it is quite striking on imaging with saccular
dilatation of most of the larger intrahepatic biliary ducts alongside focal strictures giving a beaded
appearance. There is an association with medullary sponge kidney and patients are at significantly
increased risk of developing cholangiocarcinoma.
Cholecystitis
When a gallstone becomes lodged in the neck of the gallbladder, chemical irritation from the trapped
bile leads to inflammation of the gallbladder. Sometimes this can be felt by the patient as shoulder pain
since irritation of the gallbladder is felt via C3, 4 and 5 the dermatomes of which cover the shoulder.
Mostly, however, patients complain of right upper quadrant pain. With an accurate history this should be
distinguishable from the pain caused by biliary colic, the latter being intermittent in nature and lasting
less than six hours per episode.
On ultrasound the earliest signs will be of gallstones in the presence of a sonographic Murphy sign.
Clinically Murphy sign is maximal tenderness when palpating over the gallbladder and the addition of
ultrasound allows for greater specificity in this regard. The presence of pericholecystic fluid and
increasing thickness of the gallbladder wall (>3mm) are also common findings, but come slightly later
on. With CT similar findings can be seen with the addition of enhancement of the adjacent liver due to
reactive hyperaemia. The presence of gallstones can be easily masked on CT since they are often of
equal density to the bile.
Nuclear medicine tests would not usually be part of the index management of cholecystitis however can
be used to determine cytic duct patency. Non-visualisation of the gallbladder at four hours following
injection of 99mTc-HIDA is reported to be 99% specific in the diagnosis of cholecystitis.
Acalculous cholecystitis can also occur, often in the setting of an already unwell patient on ITU. It will
present as generic sepsis and it is usually down to the clinical team to retain a high index of suspicioun.
It is thought to be a consequence of low blood flow in the cystic artery.
Emphysematous cholecystitis signifies a gas-producing organism such as Clostridium or E-coli.
Appearances are striking on imaging with ring-down or reverberation artefacts on ultrasound and mural
gas seen on CT. Patients are typically (but not exclusively) diabetic or suffering from a debilitating
condition. Unfortunately the mortality rate is significantly higher than for non-emphysematous
cholecystitis.
Mirizzi syndrome can present as cholecystitis and occurs when the common hepatic duct is obstructed
by the mechanical pressure of a stone within the cystic duct. It follows that patients whose cystic duct
happens to insert low in the course of the common hepatic duct are predisposed to this condition.
Pseudomyxoma peritonei
Pseudomyxoma peritonei is the term used to denote the peritoneal cavity filled with mucinous fluid
secondary to intraperitoneal rupture of a mucinous tumour. Most commonly the original tumour is an
appendix mucocoele. Scalloping of the liver by loculated ascites is typical. It is more common in women
than men and patients range in age from their 20s to 80s.
1.
2.
The peritoneal cavity is the potential space between the parietal and visceral peritoneum. It is the
largest serosal sac in the body and secretes approximately 50 mls of lubricating fluid daily. Ascites is the
accumulation of excessive amounts of fluid within the peritoneal cavity.
The peritoneal cavity can be divided into the greater and lesser peritoneal sacs. The greater sac
comprises the majority of the peritoneal cavity. The lesser sac is smaller and lies posterior to the
stomach and lesser omentum.
The greater sac can be further subdivided into two compartments by the mesentery of the
transverse colon (the transverse mesocolon):
The supracolic compartment – which lies above the transverse mesocolon
The infracolic compartment – which lies below the transverse mesocolon
The infracolic compartment is further subdivided into the left and right infracolic spaces by
the mesentery of the small intestine.
The contents of the supracolic and infracolic compartments is shown in the table below:
Supracolic compartment Infracolic compartment
Stomach
Small intestine
Liver
Ascending colon
Spleen
Descending colon
The lesser sac is also referred to as the omental bursa and lies posterior to the stomach. It allows
the stomach to move freely against the structures posterior and inferior to it. It is connected with the
greater sac through an opening called the epiploic foramen
Pneumatosis cystoides intestinalis
This term is used to describe the presence of multiple gas-filled cysts within the colonic wall. It is a form
of pneumatosis coli but whereas the latter has more sinister connotations, usually ischaemia, patients
with pneumatosis cystoides intestinalis may be completely asymptomatic. In around 15% of patients no
cause is identified (i.e. idiopathic) but it is also thought to be akin to gastric emphysema arising in
patients with long-term respiratory conditions causing excessive coughing.
Differential diagnosis for intramural gas
1.
Ch = Chronic respiratory condition
I = Ischaemia
P = Post-traumatic
S = Scleroderma or steroids
Swyer-James syndrome
In this condition, normal development of the infant lung is impeded by bronchiolitis (viral or mycoplasma)
at an early age, with superadded acute airspace destruction. Consequently the affected lobe is small
and lucent on the CXR due to air trapping. It is a differential diagnosis for a unilateral lucent hemithorax,
along with a pneumothorax, very large pulmonary emboli and causes of decreased chest wall
musculature such as Poland syndrome or, historically, polio. In an an exam situation Swyer-James
syndrome is usually given as a teenage or young adult patient with a history of recurrent LRTIs. Air
trapping, and bronchiectasis can also be described.
Volvulus
In various areas of the abdomen it is possible for parts of the bowel to twist on themselves causing
compromise to their own vascular supply and leading to a closed loop obstruction. This is termed a
volvulus. The two most common locations are at redundant loops of sigmoid colon and the caecum but
the transverse colon can also volve, as can the entire small bowel and the stomach. The following signs
are mainly described with respect to sigmoid volvulus but there is some cross-over to the other types
too.
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Coffee-bean sign: two opposing dilated loops with a distinct midline crease
Three-line sign: the two outer walls of the loops and the central line
Bird-of-prey sign: on a barium enema, the beak-like outline of the most superior extent that the barium
reaches before the volvulus
Whirl sign: on CT, the twisted mesenteric vessels at the centre of the torsion
Sigmoid volvulus is often associated wtih elderly patients who have chronic constipation but patients
with any age can develop sigmoid redundancy thereby making them prone to a sigmoid volvulus.
Pregnancy and institutionalisation are also risk factors.
In cases of caecal volvulus the haustral markings are preserved even when there is significant dilatation
however in the sigmoid colon the haustra can flatten out under endo-tension. This is a specific sign for a
sigmoid volvulus.
Chiliaditi sign is seen on a chest x-ray where the transverse colon rises up to sit under the right
hemidiaphragm, between it and the liver. It is a mimic for subdiaphragmatic gas.
Sigmoid
Older patients
Caecal
Younger patients (20-40s)
70% of cases
20% of cases
Ahaustral
Haustral
Loops converge to the left Loops convervge to the right lower
pelvis
quadrant or left upper quadrant
Bezoar
The word bezoar comes from the Persian word for antidote (JK Rowling had a point), and quite apart
from their usage in the fictional wizarding world of Harry Potter the term is used to describe concretions
of ingested matter which have collected in the stomach or other part of the gastrointestinal tract.
A phytobezoar - this consists of undigested fibrous plant matter
A trichobezoar – this consists of ingested hair and occurs almost exclusively in women, 80% of whom
are under the age of 30.
A number of conditions can predispose patients to developing a bezoar; chiefly those which impede
passage through the stomach due to either the sheer quantity of ingested matter, the lack of gastric
motility or an outright gastric outlet obstruction.
Underlying causes of a bezoar
Vagotomy
Diabetes
Poor gastric motility (vagotomy,
diabetes, connective tissue
disorder)
Connective tissue disorder
Myotonic dystrophy
Hypothyroidism
Insufficient mechanical or
acid/protease action
Gastrectomy
Dental problems
Ulcers
Gastric outlet obstruction
Strictures
On a fluoroscopic study the bezoar will appear as a large intraluminal filling defect which moves with
patient positioning and does not appear to be fixed to the wall at any point. Often on CT the bezoar will
be strikingly obvious as a large but smoothly rounded heterogenous mass within the stomach. Locules
of gas within the mass are common.
Bouveret syndrome
This is akin to a gallstone ileus where the level of obstruction is the proximal duodenum and there is
consequential gastric outlet obstruction.
Mirizzi syndrome
Obstruction of the common bile duct by extrinsic compression from a gallstone sitting within the cystic
duct is called Mirizzi syndrome.
Duplication cysts
Around quarter of duplication cysts occur in each of the ileum, oesophagus and colon (of these the
ileum is the most common). The remaining quarter includes the stomach, jejunum and duodenum. A
barium study may show a filling defect reminiscent of an extrinsic mass and if it is visible on ultrasound it
would appear as a rounded or tubular cystic mass. For the most part however the diagnosis can be
made on CT or MRI. The thin wall of the cyst may enhance slightly on CT and on MRI they will return
high T2 signal, much as would be expected from a cystic structure.
Stromal tumour also known as GIST (Gastrointestinal stromal tumour)
Particularly when of low staging at resection, these tumours carry an excellent prognosis. Unfortunately
around half of patients present with metastatic disease owing to the relatively indolent nature of the
primary lesion. Tumour histology is used to guide follow up and newer antibody therapies have also
improved outcomes significantly.
70% of GISTs occur in the stomach with most of the remainder being found in the small bowel. Clinical
presentation varies slightly with the exact location but dysphagia and early satiety are common, as are
sequelae from mucosal ulceration and bleeding. They can occur as a feature of neurofibromatosis type
1 and are also discussed in connection to the Carney triad (Not to be confused with Carney syndrome).
On imaging they may be occult or appear as a well-circumscribed submucosal mass. The low
attenuation is attributable to central necrosis within the mass. Characteristically however they tend to
enlarge extraluminally into the lesser sac, gastrosplenic or gastrohepatic ligaments. Of note, lymph node
enlargement is specifically not a feature and an alternative diagnosis should be sought if lymph node
enlargement is present.
1.
2.
3.
Carney Triad
Pulmonary chondromas
Gastric leiomyosarcoma (GIST)
Extra-adrenal paraganglioma
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Carney syndrome
Atrial myxoma
Facial/buccal pigmentation
Sertoli tumour of the testis
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Pituitary adenoma
The abdominal lymph nodes can be broadly divided into pre-aortic and para-aortic groups, depending
upon their relationship to the aorta.
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The pre-aortic nodes lie anterior to the aorta and lie around the origins of the visceral (anterior)
arteries. They drain the gastrointestinal tract and its accessory viscera (liver, spleen and pancreas).
These nodes can be further divided into three groups, each lying near to the origins of their respective
artery:
Coeliac lymph nodes
Superior mesenteric lymph nodes
Inferior mesenteric lymph nodes
All of the efferent lymphatics from the pre-aortic nodes drain into the intestinal trunk, which in turn
drains into the cisterna chlyi.
The structures drained by each of these groups is summarized in the table below:
Group
Coeliac lymph nodes
Structures drained
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Superior mesenteric lymph nodes
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Inferior mesenteric lymph nodes
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Stomach
Most of the duodenum
Liver and biliary tree
Pancreas
Spleen
Part of the duodenum
Jejunum and ileum
Caecum and appendix
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Upper rectum
Arrangement of the abdominal lymph nodes (from Gray’s Anatomy)
Oesophagitis
Inflammation of the oesophagus usually presents with severe pain on swallowing (odynophagia). There
are many different aetiologies but there are a few features which can help separate the differential
diagnoses on imaging.
Aetiology
Features
Immunocompromised patients (including long term steroid therapy)
Candidiasis
Upper half of the oesophagus
Irregular, longitudinal plaques with normal mucosa in between
Fulminant
candidiasis
Patients with AIDs
Shaggy outline from a pseudomembrane of joined-together plaques
Immunocompromised patients
Herpes simplex Flu-like symptoms
Multiple small ulcers, each may have a halo of oedema
CMV / HIV
oesophagitis
One large ulcer
These two are indistinguishable from one another by appearance
Ingestion of corrosive substance
Caustic
Affects middle and lower thirds
Progression from oedema to ulceration to scarring over days
Barrett
oesophagitis
Squamous metaplasia of distal oesophagus in response to reflux
Long strictures
Reticular mucosal pattern
Ulcers at sites of extrinsic compression in the mid oesophagus
Drug-induced
Patients taking medication without enough water immediately prior to going
to bed
Idiopathic
eosinophilic
oesophagitis
History of atopy usually present
Specific ring-like indentations to the oesophagus
Glycogen acanthosis
This condition is caused by benign age-related squamous hyperplasia but, based on its imaging
features, a differential diagnosis for candidiasis. On a barium swallow there will be small rounded white
plaques in a random distribution, predominantly affecting the middle and upper oesophagus. Patients
are typically middle aged or elderly
Abdominal wall hernias
Hernias can occur at any age but are increasingly prevalent with increasing age. Conditions which
increase intra-abdominal pressures predispose patients to developing hernias. These might be entities
such as constipation or respiratory conditions associated with excess coughing such as COPD.
Hernia
Femoral
Landmarks
Inferolateral to the pubic tubercle and medial to
the femoral vein
Feature
Direct inguinal
Superolateral to the pubic tubercle, medial to the
Through Hesselbach triangle
inferior epigastric vein
Indirect inguinal
Superolateral to the pubic tubercle and lateral to
Most common abdominal hernia
the inferior epigastric vein
Obturator
Between pectineus and obturator externus
muscles, through the obturator foramen
Spigelian
Inferolateral abdominal wall defect, lateral to the May be congenital and associated with
rectus abdominus muscle
cryptorchidism
More common in women
Rare
Indirect inguinal hernias pass through the inguinal canal, taking in both the deep and superficial rings as
they do. The deep ring is lateral to the internal epigastric vessels.
Direct inguinal hernias protrude through the conjoint tendon medial to the internal epigastric vessels and
enter the scrotal sac through the superficial ring. They pass through the Hesselbach triangle which is
composed of the inferior epigastric vessels, rectus abdominus and the inguinal ligament.
he lymphatic drainage of the liver is via superficial and deep lymph vessels. The majority of these
lymph vessels join those in the porta hepatis before entering the hepatic lymph nodes.
The majority of the efferent lymph vessels from the hepatic lymph nodes drain into the coeliac lymph
nodes.
Some of the deep lymphatic vessels follow the hepatic veins to the vena caval foramen in the
diaphragm to drain into the phrenic lymph nodes.
The lymphatic vessels on the ‘bare area’ of the liver (where there is no peritoneum present on the
diaphragmatic surface) pass through the vena caval foramen to drain into the phrenic and mediastinal
lymph nodes.
Lymph from the phrenic and mediastinal nodes subsequently drains into the right lymphatic duct and
thoracic duct.
Fold thickness
Much is made on barium examinations, of the thickness of the folds and whether there is any nodularity.
Such features can be helpful in teasing apart the possible diagnoses in similar cases.
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Coeliac disease – dilatation without increase in fold thickness
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Scleroderma – dilatation without loss of valvulae conniventes, prolonged transit time
Zollinger-Ellison syndrome – dilatation of the proximal small bowel due to hypersecretion
Small bowel lymphoma – fold thickening and lymph node enlargement
Mastocytosis – nodular fold thickening with sclerotic bone lesions
Crohn disease – nodular fold thickening
Whipple disease – thickened folds (+/- microndularity) without dilatation, with normal transit time
Whipple disease also known as intestinal lipodystrophy
Infection with Tropheryma whipplei causes a migratory arthralgia with jejunal fold thickening leading to
malabsorption and is known as Whipple disease. Skin hyperpigmentation is often described and
peripheral lymph nodes may be enlarged. Micronodularity does occur on the thickened folds but
crucially there is little or no small bowel dilatation and a normal transit time. Obstruction of the
lymphatics leads to low density lymph nodes appearing on CT. PAS positive macrophages confirm the
infection.
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Differential diagnosis for lymph nodes
of low attenuation
Coeliac disease – cavitating mesenteric
lymph node syndrome
Tuberculosis
Whipple disease
Lymphoma
Necrotic metastases
Small bowel lymphoma
Malignancies of the small bowel are rare but lymphoma is the most common of these. Coeliac disease,
infection with H. Pylori and AIDs both predispose patients to developing small bowel lymphoma.
Perhaps surprisingly patients do not present with obstruction even when the tumour burden is large,
similarly neoplastic perforation is not common. Instead patients present with insidious symptoms or
haemorrhage. On imaging there is (sometimes extensive) thickening of the bowel wall, often with
associated lymph node enlargement.
Mastocytosis
Mast cells store histamine (among other things). Where they exist in excess the resultant symptoms fit
with excess histamine release. Patients complain of nausea, vomiting, diarrhoea, hypotension, flushing
and abdominal pain. Asthma-type symptoms can also occur. On imaging hepatosplenomegaly and
lymph node enlargement are common. The walls of the small bowel become thickened and
malabsorption occurs too. Mastocytosis is also a cause of bony sclerosis.
Causes of bony sclerosis
Hyperthyroidism
Metabolic
Hyperparathyroidism
Pyknodysostosis
Congenital
Osteopetrosis
Lymphoma
Malignant
Leukaemia
Sickle cell disease
Haematological
Myelofibrosis
Mastocytosis
Other
Fluorosis
Paget disease
Eosinophilic enteropathy
This is a rare condition caused by infiltration of eosinophils into the wall of the small bowel. Patients
often suffer from food allergies and experience multiple attacks of abdominal pain, diarrhoea and
vomiting in a relapsing/remitting pattern. Blood eosinophil levels are usually raised. On imaging the folds
of the small bowel can appear thickened.
Scleroderma
Scleroderma is a multi-system connective tissue disease leading to fibrosis and loss of smooth muscle.
In the gastrointestinal system this leads to the hidebound sign (also known as stacked coin sign) where,
despite being dilated in calibre, the small bowel still retains the valvulae conniventes which would
otherwise be effaced. This is thought to result from fibrosis of the longitudinal layer causing
foreshortening along the long axis. In the small bowel there can also be the formation of square-shaped
broad-based pseudodiverticulae on the mesenteric border of the bowel is seen owing to uneven atrophy
of the smooth muscle there. A prolonged transit time would be ususal. Pseudosacculations (widemouthed diverticulae) are found in the colon but this time on the antimesenteric border.
Perianal fistulae
Most perianal fistulas are throught to result from an initial infection in an intersphincteric gland.
Abscesses here would normally drain into the anal canal but fistulous tracts can develop if the glands is
occluded. Slices should be obtained axially to the path of the rectum. Owing to the inflammation and
granulation tissue in a fistulous tract there is avid enhancement with gadolinium. T1 post-contrast
images are therefore the best means by which to assess patients with active disease. If the high signal
persists on unenhanced T1 images it is likely to be due to the presence of haemorrhage. STIR
sequences can also be useful to track the high signal of a fistulous tract but spatial resolution is usually
poorer. Chronic fistulas develop fibrotic tissue which becomes low in signal on both T1 and T2.
Perianal fistulae are classified according to their relationship to the external sphincter with intersphincteric fistulae being the most common since the external sphincter provides a reasonably robust
barrier to the spread of an infection.
Perianal fistula - Park's classification
Does not cross the external sphincter, remains
70%
Inter-sphincteric
medial to it
Crosses the external sphincter (as well as the
internal one)
Trans-sphincteric
25%
Supra-sphincteric
Courses superiorly over the top of the external
5% sphincter and exits the pelvis through the
puborectalis muscle
Extra-sphincteric
Begins higher up in the rectum, avoids both
<1% sphincters, exits the pelvis through the levator ani
complex and into the ischiorectal fossa
Submucosal /
superficial
-
Not included in the classification. Remains
superficial to both sphincters.
Image adapted from Wikipedia(link is external)
Courtesy of Armin Kübelbeck CC BY-SA 4.0(link is external)
Polyposis syndromes – intussusception is a significant risk
Turcot syndrome
This is a subtype of Familial Adenomatous Polyposis (FAP) and inherited in an autosomal recessive
fashion. The polyps are adenomatous and largely colonic. They are subject to the adenoma-carcinoma
sequence and thus most patients develop cancer before the reach 40 years of age. Brain tumours are
also part of this disease; supratentorial glioblastomas or medulloblastomas. A patient with diarrhoea and
seizures would be a typical scenario in which Turcot syndrome is diagnosed.
Peutz-Jegher syndrome
Around half of cases are inherited in an autosomal dominant fashion but the rest are sporadic mutations
to a tumour suppressing gene on chromosome 11. Innumerable hamartomatous polyps develop
throughout the gastrointestinal tract. For a firm diagnosis there should be at least 100 polyps but usually
there are far more. In the large bowel the polyps can be larger and more pedunculated, putting the
patient at risk of intussusceptions. Patients are also at greater risk of many different cancers (upper GI,
ovary, thyroid, testis, pancreas, breast). Mucocutaneous pigmentation is classic.
Cowden syndrome
This is a rare hamartomatous syndrome which is inherited as an autosomal dominant defect on
chromosome 10. The polyps are predominantly (but not exclusively) in the rectosigmoid colon. There is
an association with fibrocystic disease and fibroadenomas of the breast; around half of patients have
breast pathology. There is a specific association with dysplastic cerebellar gangliocytoma also known as
Lhermitte-Duclos disease. Patients with Cowden syndrome also develop skin lesions on the head and
face called trichilemmomas which resemble tiny basal cell carcinomas.
Gardner syndrome
This is a subtype of Familial Adenomatous Polyposis (FAP) and is a triad of colonic polyps, osteomas of
the membranous skeleton (skull, maxilla, mandible) and soft tissue tumours such as desmoid tumours
of the mesentery, lipomas, fibromas, keloid scarring. Many patients have supernummary teeth and
dental caries requiring significant dental work at an early age.
Familial Adenomatous Polyposis (FAP)
The polyps in FAP are said to resemble a carpet since they are so numerous. There are invariably
colonic adenomatous polyps and around half of patients have stomach hamartomas too and a quarter of
patients have duodenal adenomas. Patients usually undergo a prophylactic total colectomy and
thereafter the greatest risk is of a periampullary carcinoma.
Syndrome
Familial
Adenomatous
Polyposis
Inheritance
AD – Ch5
Gardner syndrome AD – Ch5
Typical age at which
patients become
symptomatic
30-40s
15-30
AR – Ch10
20s
Cowden syndrome AD – Ch10
20s
Turcot syndrome
Peutz-Jegher
syndrome
AD – Ch11
25
Features
















Colonic carpet of polyps
Stomach hamartomas
Duodenal adenomas
Periampullary carcinoma
Desmoid tumours
Colonic polyps, skull osteomas, soft-tissue
tumours
Poor dentition.
Diarrhoea – colonic polyps
Seizures – glioblastoma
Rectosigmoid polyps
Fibrocystic breast disease
Dysplastic cerebellar gangliocytoma
Trichilemmomas
Hamartomatous polyps
Mucocutaneous pigmentation
Increased risk of many cancers
Contrast enhanced ultrasound (CEUS)
CEUS is cheaper than MRI and confers less risk to the patient. The patient is injected with a contrast
agent consisting of tiny microbubbles measuring micrometers in diameter. These circulate within the
patient and when insonated cause strong reflections which show up as hyperechogenicity in real time as
the bubbles wash in and out of the field of view. The microbubbles burst in time and the process can be
repeated within a few minutes if required. There is no renal toxicity and adverse reactions are very rare
meaning this is a safe procedure for almost all patients.
It is a useful technique particularly for differentiating between malignant lesions (which tend to washout
rapidly owing to their high vascularity), and benign lesions but is also useful for characterising benign
lesions such as haemangiomata or focal nodular hyperplasia by demonstrating the same enhancement
patterns which would otherwise be expected on an MRI.
The technique, having been developed with liver lesions in mind, is now being expanded to renal
lesions, testicular masses and vascular work too, among others.
Focal nodular hyperplasia (FNH)
These lesions typically occur in women in late middle age. They are not caused by oral contraceptive
use however they do enlarge in response to hormone stimulation. They are composed of hyperplastic
hepatocytes and are thought to arise when a small underlying congenital vascular malformation means
that an area of the liver receives a better blood supply and therefore grows better, thus they lack a true
capsule but can outgrow their blood supply resulting in the classical central fibrous scar which is present
in around half of cases. On imaging they do demonstrate mass effect, displacing adjacent vessels, have
marked arterial enhancement which fits in with their supposed aetiology. The central scar enhances only
on delayed sequences. On MRI they tend to return high signal on T2 weighted sequences. Their
appearance on contrast-enhanced ultrasound is interesting; the central scar enhances very early in the
arterial phase, branching out in a spoke-wheel type of appearance. During the main arterial phase the
lesions enhance strongly before becoming isoechoic in the portal venous phase.
Explanation:
Image © Medical Exam Prep
Pelvic lipomatosis
This is a curious condition which arises in young-middle aged adults. There is significant overgrowth of
fat cells within the pelvis which can lead to compression of all or any of the pelvic structures. The
bladder becomes pear shaped as the main volume is pulled superiorly. Similarly, the sigmoid is elevated
out of the pelvis and the rectum straightened to its shortest path. On CT there is a striking amount of low
attenuation fat within the pelvis and similarly this will be seen as high T1 signal on MRI.
A tailgut duplication cyst (retrorectal cystic hamartoma)
Curiously these occur almost exclusively in women. Anatomically they sit within the presacral or
retrorectal fat. They tend to be an incidental diagnosis and can be associated with bony defects within
the sacrum. Since they usually contain mucein they appear characteristically high in signal on T1
weighted MRI sequences. They can be surprisingly large and are often multiloculated.
A Tarlov cyst
A Tarlov cyst is the name given to dilatation of the posterior nerve root sheath. They follow CSF on all
sequences and can cause significant bony scalloping.
Liposarcoma
It would not be possible to diagnose this on the basis of a barium enema. It would be a differential
diagnosis for pelvic lipomatosis as seen on CT but usually contain a variable degree of soft tissue
attenuation whereas the only soft tissue attenuation seen with pelvic lipomatosis results from anatomical
distortion of normal structures.
Ulcerative colitis
On a barium enema the colon and rectum can appear featureless – the so-called lead pipe appearance.
Otherwise the mucosal surface is said to have a granular appearance.
Gastric lymphoma
Within the context of lymphomas of the gastro-intestinal tract, gastric lymphoma is the most common
site. The infiltrative form can give pronounced thickening of the gastric wall but the stomach’s ability to
distend is usually preserved. On a barium study rugal thickening may be evident but the degree of
gastric wall thickening is unlikely to be evident. There is no particularly predisposed part of the stomach
but typically more than half of the stomach wall area is affected, including antral involvement in most
cases. Hypersecretion and hypoalbuminaemia are not features of this condition but associated
splenomegaly is likely. The allergies in this question are a red herring.
Eosinophilic gastroenteritis
This is a relapsing, remitting condition caused by eosinophilic infiltration of the wall of the stomach. The
small bowel can also be affected and when it is, there may be accompanying hypoproteinaemia.
Involvement of the stomach however, brings ‘only’ abdominal pain, diarrhoea and weight loss. Patients
often have a concurrent history of allergies, either to food stuffs or other antigens. Within the stomach
the condition is usually confined only to the antrum and there may be rugal enlargement, polyps and
ulcers present.
Zollinger-Ellison syndrome
Zollinger-Ellison syndrome is a consequence of excess gastrin circulation, usually from a gastrinoma
within the pancreas. There is marked hypersecretion of gastric acid which predisposes the patient to
ulcer formation since the normal gastric mucosal coating becomes overwhelmed. Patients may also
experience diarrhoea but hypoproteinaemia is not a feature. On a barium study, as well as gastric
ulcers, there may be rugal enlargement and dilution of barium by the large volume of acid. Ulcers may
be present at unusual locations such as the duodenal bulb and around the ligament of Treitz
Menetrier disease
A triad of gastric glandular hypertrophy, achlorhydia and hypoproteinaemia makes up this condition. The
rugal folds become enlarged and bizarre in configuration; often said to more closely resemble the
convolutions of the cerebral cortex than the usual parallel orientation of normal gastric folds. Within the
stomach there is hypersecretion of mucus and albumin (hence hypoalbuminaemia) and this prevents
the barium from coating the mucosal surface effectively. The antrum is said to be spared although in
reality it is involved in around half of cases but where it is spared it serves as an important
discriminatory against gastric lymphoma which often does involve the antrum, as well as coming with
associated splenomegaly. In contrast to scirrhous carcinoma the stomach’s ability to distend is retained.
Gastric carcinoma
There is a subtype of gastric carcinoma called scirrhous carcinoma where instead of forming a solitary
large mass the cancer infiltrates the entire gastric wall causing thickening and shrinkage of the stomach
as well as compromising its ability to distend. The term scirrhous comes from the Greek word for hard
and relates to the fibrous indistensible change to the stomach wall. The stomach becomes leathery and
aperistaltic with appearances said to resemble an old leather drinking bottle; this appearance on a
barium study is given the term linitis plastica.
Zollinger-Ellison syndrome
Zollinger-Ellison syndrome is a consequence of excess gastrin circulation, usually from a gastrinoma
within the pancreas. There is marked hypersecretion of gastric acid which predisposes the patient to
ulcer formation since the normal gastric mucosal coating becomes overwhelmed. Patients may also
experience diarrhoea but hypoproteinaemia is not a feature. On a barium study, as well as gastric
ulcers, there may be rugal enlargement and dilution of barium by the large volume of acid. Ulcers may
be present at unusual locations such as the duodenal bulb and around the ligament of Treitz.






Differential diagnosis for hepatic capsular retraction:
Cholangiocarcinoma
Fibrolamella HCC
Metastases (breast, lung, carcinoid, colorectal)
IgG4 related disease
Iatrogenic/ post-traumatic
Cirrhosis
In many situations prostate and breast cancer metastases have similar and overlapping features and
are considered as equivalents for their respective populations. This is one where that does not hold true.
Consider that there are more sub-types of breast cancer than there are of prostate cancer. Not all types
of breast cancer cause capsular retraction.
The MRI appearance of primary and secondary haemochromatosis are not the same. The spleen
is only involved in secondary haemochromatosis.
Haemochromatosis
The primary version of this disease can be inherited in an autosomal recessive fashion. Excess dietary
iron is absorbed and this accumulates in all tissues of the body leading to various different problems.
Secondary haemochromatosis can arise if patients receive numerous blood transfusions without
sufficient chelation to mitigate against the iron overload.







Cirrhosis – the presence of the excess iron in the liver leads to unusual signal properties on an MRI
scan. Iron is paramagnetic and causes spin dephasing. T2* and T2 sequences are particularly
vulnerable to this effect but lower than expected signal will be seen on all sequences. Importantly the
signal from the spleen and bone marrow should be normal. By contrast they will be involved in cases of
transfusional siderosis.
Generalised osteoporosis
Hook like osteophytes on the radial aspect of the metacarpal heads – these are highly characteristic
Chondrocalcinosis, particularly affecting the knees
Insulin dependent diabetes
Congestive cardiomyopathy
Skin pigmentation
Wilson disease
Inherited in an autosomal recessive fashion, this disease results from an excess of copper within the
body due to the inability of the liver to excrete it. It can present in childhood with cirrhosis but later
presentations are more likely to be due to the neuropsychiatric manifestations. Clinically adolescent or
adult patients develop tremor and dysarthria due to copper deposition in the lentiform nucleus. The
classic diagnostic feature is Kayser-Fleischer pigment rings in the eyes. Radiologically the following
features can be seen:



Hepatic manifestations: The liver appears normal on MRI since fatty infiltration effectively cancels out
the paramagnetic effects of copper
Musculoskeletal manifestations: Generalised osteoporosis, subarticular cysts, chondrocalcinosis and
arthropathy which can mimic CPPD
CNS manifestations: White matter atrophy and T2 hyperintensities predominantly affecting the basal
ganglia and thalami. T1 signal is also high in these areas, differentiating it from many of the other basal
ganglia disorders. There is a classical feature of ‘sparing of the red nucleus’ leading to an appearance
known as the giant panda sign at the level of the pons.
Gaucher disease
This lysosomal storage disease is usually inherited in an autosomal recessive fashion and is around 100
times more common in Ashkenazi Jews than it is in the rest of the population. There is accumulation of
glycolipid in macrophage lysosomes. The infantile form is universally lethal before 24 months of age but
the adult form may be asymptomatic at diagnosis and is typically diagnosed in young adulthood if not
earlier. Hepatosplenomegaly is common and co-existent with thrombocytopaenia and anaemia
secondary to bone marrow failure. Osteonecrosis occurs in the femoral or humeral heads leaving
serpiginous sclerotic areas or a bone-within-bone appearance. Modelling deformities such as the
Erlenmeyer flask deformity (Flared metaphysis + diaphyseal thinning) also occur and are considered
characteristic.
Sickle cell disease
The signal from the spleen may be affected by haemosiderin deposition due to haemolysis within the
spleen but the liver is unlikely to be affected.
Amiodarone therapy
Amiodarone is an anti-arrhythmic drug which contains iodine (am-IOD-arone). Consequently, as it
accumulates in the liver, it can cause significant increase in density to the liver on a CT scan.
Infective colitis
Infective colitis causes oedematous mural thickening and mural enhancement with the different
underlying organism affecting slightly different segments of bowel (albeit with much overlap). Pericolic
fat stranding and ascites are variably seen.
Location
Diffuse involvement of whole colon
Organism
CMV and e-coli
Right sided colon
Salmonella and shigella
Left sided colon
Schistosomiasis
Rectosigmoid colon
Gonorrhoea, herpes, Chlamydia (LGV
The correct pairings are as follows:





Immediate uniform enhancement which washes out - malignant lesion
Peripheral nodular enhancement with gradual filling in - haemangioma
Spoke wheel enhancement of a central scar - fibrous nodular hyperplasia
Gradual uniform enhancement - benign lesion
Arterial enhancement with a non-enhancing central scar - fibrolamellar hepatocellular carcinoma
Contrast enhanced ultrasound (CEUS)
CEUS is cheaper than MRI and confers less risk to the patient. The patient is injected with a contrast
agent consisting of tiny microbubbles measuring micrometers in diameter. These circulate within the
patient and when insonated cause strong reflections which show up as hyperechogenicity in real time as
the bubbles wash in and out of the field of view. The microbubbles burst in time and the process can be
repeated within a few minutes if required. There is no renal toxicity and adverse reactions are very rare
meaning this is a safe procedure for almost all patients. The most significant limitation is the location of
the lesion; if the lesion cannot be seen with B-mode ultrasound then it cannot be interrogated with
CEUS.
It is a useful technique particularly for differentiating between malignant lesions (which tend to washout
rapidly owing to their high vascularity), and benign lesions but is also useful for characterising benign
lesions such as haemangiomata or focal nodular hyperplasia by demonstrating the same enhancement
patterns which would otherwise be expected on an MRI.
The technique, having been developed with liver lesions in mind, is now being expanded to renal
lesions, testicular masses and vascular work too, among others.
As a general rule, if the lesion can be seen on ultrasound, it can be investigated with CEUS however
lesions smaller than 10mm are often challenging in this regard. In any case, an anechoic lesion (i.e. a
cyst) needs no further investigation. Lesions close to the diaphragm (Segments VII and VIII in particular)
are difficult to see with ultrasound at the best of times.
The anatomical relations of each part of the colon are shown in the table below:
Section of colon
Anterior relations
Posterior relations
Quadratus lumborum
Anterior abdominal wall Iliacus
Ascending colon
Small intestine
Right kidney
Greater omentum
Iliohypogastric nerve
Ilioinguinal nerve
Transverse colon
Anterior abdominal wall Duodenum
Greater omentum
Jejunum
Ileum
Head of pancreas
Quadratus lumborum
Anterior abdominal wall Iliacus
Descending colon Small intestine
Greater omentum
Left kidney
Iliohypogastric nerve
Ilioinguinal nerve
Urinary bladder
Rectum
Sigmoid colon
Uterus (females)
Sacrum
Upper vagina (females)
Portal circulation
Systemic circulation
Clinical condition
Left gastric vein
Azygous vein
Oesophageal varices
Para-umbilical veins Inferior epigastric vein
Superior rectal vein
Caput medusae
Middle and inferior rectal veins Haemorrhoids
The key differentiator between dorsal pancreatic agenesis and lipomatosis is the absence of the
pancreatic duct. If no duct is visualised, this suggests agenesis over lipomatosis. Furthermore,
lipomatosis usually affects the whole gland and does not spare the pancreatic head. Dorsal agenesis is
much more common than total pancreatic agenesis.
The most common cause of pancreatic lipomatosis in children is cystic fibrosis, the second most
common cause is Shwachman-Diamond syndrome. Additional features of this condition include short
stature with metaphyseal chondroplasia and eczema. Steroid use and Cushing syndrome are also
associated with lipomatosis.
Neutropenic colitis also known as typhilitis
The name typhilitis comes from the greek typhlos meaning blind ending sac and relates to the
involvement of the caecum. Although the rest of the bowel can be affected it is the caecum which bears
the brunt of this disease. The caecal wall becomes thickened (to >4mm) and markedly oedematous; the
appearance may be so extreme that it may seem more like a large fluid density mass than part of the
bowel. Barium studies carry a significant risk of perforation and should be avoided but would show
oedema and severe ulceration. On CT transmural oedema with adjacent fat stranding is found. It
develops in immunocompromised patients, in particular those undergoing induction chemotherapy prior
to bone marrow transplantation.
Radiation enteritis
Acutely following radiation therapy there is cell death of the rapidly turning over mucosal cells of the
bowel wall, and particularly of the terminal ileum. This leads to ulceration and mucosal/submucosal
oedema.
Subacutely to chronically the radiation damage leads to endarteritis obliterans and chronic mesenteric
ischaemia. The bowel does heal but fibrous changes persist and strictures can form. There is no link in
severity between the acute and chronic forms; the presence or absence of the one does not predict the
other.
The bowel loops can be seen to be fixed in the same positions on sequential contrast studies by a
desmoplastic response within the mesentery. Patients complain of crampy abdominal pain from
intermittent obstruction as well as diarrhoea.
Tuberculosis
Abdominal tuberculosis most commonly affects the ileocaecal junction with thickening of the ileocaecal
valve and narrowing of the terminal ileum. This can be seen on fluoroscopic examination as the
Fleischner sign or umbrella sign where the gaping ileocaecal valve abuts the thin, strictured terminal
ileum. Local lymph node enlargement with or without central low attenuation to the lymph nodes may be
seen on CT. Multiple different lesions in multiple sites (i.e. skip lesions) is also a feature and a
characteristic feature is of elevation of the margins of an ulcer which follow the orientation of lymphoid
follicles. In the colon this means the margins are elevated in the transverse plane but in the terminal
ileum they are longitudinal.
The involvement of the ileocaecal valve and the presence of skip lesions means that a key differential
diagnosis is Crohn disease. Over half of cases of abdominal tuberculosis will have concurrent ascites
whereas this is a relatively rare feature for Crohn disease and can be used as a discriminator.
Specifically relating to the stomach, tuberculosis can cause pyloric stenosis, multiple deep ulcers on the
lesser curve, and linitis plastic type narrowing of the antrum.
Crohn disease
Crohn disease is characterised by discontinuous (skip lesions) transmural non-caseating granulomatous
inflammation. By contrast, ulcerative colitis is characterised by continuous mucosal inflammation. Crohn
disease is usually diagnosed in adolescence or young adulthood and patients present with non-specific
abdominal pains, diarrhoea, weight loss and anaemia. Crohn disease can affect any part of the entire
length of the gastrointestinal tract, in contrast to ulcerative colitis which affects only the colon, but owing
to the high concentration of lymphoid tissue in the terminal ileum the vast majority of patients will have
terminal ileal involvement, in particular thickening of the iliocaecal valve. Aphthous ulceration is common
and on endoscopy a cobblestone appearance to the mucosa can be seen where the thickened and
oedematous wall is broken up by deep longitudinal fissures. Deep ‘rosethorn’ ulcers can be seen on
fluoroscopic studies. Strictures and fistulae characterise the chronic sequela of this disease.
Conditions associated with Crohn disease
Erythema nodosum
Gallstones
Oxalate ureteric calculi
Sclerosing cholangitis
Cholangiocarcinoma
Small bowel carcinoma
A Zenker diverticulum
A dehiscence in the cricopharyngeal muscle (at an area called the Killian triangle, thereby Killian
dehiscence) allows the protrusion of mucosa and submucosa through it to form a diverticulum. Food
and fluid can collect in these leading to symptoms of halitosis, aspiration of undigested food (leading to
aspiration pneumonia) and the pressure effect of the diverticulum causes dysphagia. They occur in
elderly women in particular. On barium swallows they can be seen as extension of barium posteriorly
from the oesophagus, around the level of C5-6. Occasionally they can be seen as an air-fluid level in the
neck on a chest x-ray.
Intramural pseudodiverticulosis
This is a feature of candidal oesophagitis. Tiny diverticulae are found scattered along the length of the
oesophagus and on a barium swallow the appearance can be quite impressive! Like most candidal
infections oesophagitis is most common in patients with suppressed immunity including patients with
diabetes, on steroids, or chemotherapy.
Gardner syndrome
This is a subtype of Familial Adenomatous Polyposis (FAP) and is a triad of colonic polyps, osteomas of
the membranous skeleton (skull, maxilla, mandible) and soft tissue tumours such as desmoid tumours
of the mesentery, lipomas, fibromas, keloid scarring. Many patients have supernummary teeth and
dental caries requiring significant dental work at an early age.
Cowden syndrome
This is a rare hamartomatous syndrome which is inherited as an autosomal dominant defect on
chromosome 10. The polyps are predominantly (but not exclusively) in the rectosigmoid colon. There is
an association with fibrocystic disease and fibroadenomas of the breast; around half of patients have
breast pathology. There is a specific association with dysplastic cerebellar gangliocytoma also known as
Lhermitte-Duclos disease. Patients with Cowden syndrome also develop skin lesions on the head and
face called trichilemmomas which resemble tiny basal cell carcinomas.
Turcot syndrome
This is a subtype of Familial Adenomatous Polyposis (FAP)and inherited in an autosomal recessive
fashion. The polyps are adenomatous and largely colonic. They are subject to the adenoma-carcinoma
sequence and thus most patients develop cancer before the reach 40 years of age. Brain tumours are
also part of this disease; supratentorial glioblastomas or medulloblastomas. A patient with diarrhoea and
seizures would be a typical scenario in which Turcot syndrome is diagnosed.
Peutz-Jegher syndrome
Around half of cases are inherited in an autosomal dominant fashion but the rest are sporadic mutations
to a tumour suppressing gene on chromosome 11. Innumerable hamartomatous polyps develop
throughout the gastrointestinal tract. For a firm diagnosis there should be at least 100 polyps but usually
there are far more. In the large bowel the polyps can be larger and more pedunculated, putting the
patient at risk of intussusceptions. Patients are also at greater risk of many different cancers (upper GI,
ovary, thyroid, testis, pancreas, breast). Mucocutaneous pigmentation is classic.
Familial Adenomatous Polyposis (FAP)
The polyps in FAP are said to resemble a carpet since they are so numerous. There are invariably
colonic adenomatous polyps and around half of patients have stomach hamartomas too and a quarter of
patients have duodenal adenomas. Patients usually undergo a prophylactic total colectomy and
thereafter the greatest risk is of a periampullary carcinoma.
Syndrome
Familial
Adenomatous
Polyposis
Inheritance
AD – Ch5
Gardner syndrome AD – Ch5
Typical age at which
patients become
symptomatic
30-40s
15-30
AR – Ch10
20s
Cowden syndrome AD – Ch10
20s
Turcot syndrome
Peutz-Jegher
syndrome
AD – Ch11
25
Features
















Colonic carpet of polyps
Stomach hamartomas
Duodenal adenomas
Periampullary carcinoma
Desmoid tumours
Colonic polyps, skull osteomas, soft-tissue
tumours
Poor dentition.
Diarrhoea – colonic polyps
Seizures – glioblastoma
Rectosigmoid polyps
Fibrocystic breast disease
Dysplastic cerebellar gangliocytoma
Trichilemmomas
Hamartomatous polyps
Mucocutaneous pigmentation
Increased risk of many cancers
Target lesions (also known as Bull's eye lesions) in the liver are usually discussed in the context of an
ultrasound scan. All of the options listed could produce one or other kind of appearance.
Liver abscesses can demonstrate a variety of appearances from one patient to the next although a
Bull's eye appearance is common. In particular candidal abscesses often show a target appearance and
have a strong association with induction chemotherapy regimens prior to bone marrow transplantation.
Candidal infections anywhere in the body tend to be characterised by micro-abscess formation and the
liver is no different. If the abscesses are sufficiently large then they may be appreciated on CT. Necrotic
areas on CT are low in attenuation and surrounding inflammatory change will be hyperenhancing giving
rise to a CT target type appearance.
The stomach receives an extensive arterial supply that is derived from the coeliac trunk and its
branches. Anastomoses form along the lesser curvature by the left and right gastric arteries and long
the greater curvature by the left and right gastro-omental arteries.
The arteries supplying the stomach are:





The left gastric artery – arises directly from the coeliac trunk
The right gastric artery – is a branch of the common hepatic artery, which arises from the coeliac trunk
The left gastro-omental artery – is a branch of the splenic artery, which arises from the coeliac axis
The right gastro-omental artery – is a terminal branch of the gastroduodenal artery, which arises from
the common hepatic artery
Short gastric arteries – arise from the distal end of the splenic artery
Focal steatosis also known as focal fatty infiltration
The liver plays a small role in fat storage, and subtle variation in blood supply and drainage between
different areas can lead to variations in the amount of fat in those areas. Focal fatty change is very
common and has a geographic appearance on all imaging modalities, with a lack of mass effect (i.e.
preservation of the vascular architecture). It can occur anywhere within the liver but is classically found
adjacent to the falciform ligament (i.e. segments II, III and IV). Fat-identifying sequences on MRI can be
very useful to confirm the diagnosis with signal drop out on out-of-phase images. Focal fatty sparing on
the other hand appears as the inverse of this and on CT will be seen as isoattenuation on a background
of a diffusely hypoattenuating liver. On ultrasound the liver will be diffusely hyperechoic when compared
to the right kidney, and the spared area will be hypoechoic.
Steatosis can be focal or diffuse. In this example of diffuse steatosis there is signal drop out in the whole
of the liver on the out-of phase images:
Image sourced from Wikipedia(link is external)
Courtesy of SpinDfazor CC BY-SA 3.0(link is external)
Haemochromatosis
The primary version of this disease can be inherited in an autosomal recessive fashion. Excess dietary
iron is absorbed and this accumulates in all tissues of the body leading to various different problems.
Secondary haemochromatosis can arise if patients receive numerous blood transfusions without
sufficient chelation to mitigate against the iron overload.







Cirrhosis – the presence of the excess iron in the liver leads to unusual signal properties on an MRI
scan. Iron is paramagnetic and causes spin dephasing. T2* and T2 sequences are particularly
vulnerable to this effect but lower than expected signal will be seen on all sequences. Importantly the
signal from the spleen and bone marrow should be normal. By contrast they will be involved in cases of
transfusional siderosis.
Generalised osteoporosis
Hook like osteophytes on the radial aspect of the metacarpal heads – these are highly characteristic
Chondrocalcinosis, particularly affecting the knees
Insulin dependent diabetes
Congestive cardiomyopathy
Skin pigmentation
Wilson disease
Inherited in an autosomal recessive fashion, this disease results from an excess of copper within the
body due to the inability of the liver to excrete it. It can present in childhood with cirrhosis but later
presentations are more likely to be due to the neuropsychiatric manifestations. Clinically adolescent or
adult patients develop tremor and dysarthria due to copper deposition in the lentiform nucleus. The
classic diagnostic feature is Kayser-Fleischer pigment rings in the eyes. Radiologically the following
features can be seen:



Hepatic manifestations: The liver appears normal on MRI since fatty infiltration effectively cancels out
the paramagnetic effects of copper
Musculoskeletal manifestations: Generalised osteoporosis, subarticular cysts, chondrocalcinosis and
arthropathy which can mimic CPPD
CNS manifestations: White matter atrophy and T2 hyperintensities predominantly affecting the basal
ganglia and thalami. T1 signal is also high in these areas, differentiating it from many of the other basal
ganglia disorders. There is a classical feature of ‘sparing of the red nucleus’ leading to an appearance
known as the giant panda sign at the level of the pons.
Amiodarone therapy
Amiodarone is an anti-arrhythmic drug which contains iodine (am-IOD-arone). Consequently, as it
accumulates in the liver, it can cause significant increase in density to the liver on a CT scan.
Osler-Weber-Rendu
Classically patients have telangiectasia on the skin, particularly around the oral and nasal mucosa. With
regards to the liver, cirrhosis and a grossly dilated hepatic artery are textbook features. Raised portal
venous pressure is common if the liver is involved.
Cystic fibrosis
Steatosis due to untreated malabsorption and features of portal hypertension accompany the classical
feature of fatty infiltration of the liver.
Autoimmune hepatitis
Starts as hepatomegaly and jaundice but progresses to cirrhosis with no specific or classical features.
Haemochromatosis Very low T2 signal, due to iron accumulation, coupled with cirrhotic change.
Anabolic steroid use
Anabolic steroid use can cause non-alcoholic fatty liver disease. Hepatic adenomas are also associated
with anabolic steroid use.
In an ideal world every trainee radiologist would have all the intricacies of staging for all tumour types
committed to memory. A qualified subspecialist radiologist could reasonably be expected to be
extremely familiar with the staging for cancers within their remit but for the majority of trainees it is
simply not practical to memorise each and every staging scheme. As an overall strategy, the most
important stages to understand are those which change the management for patients. Of note with lung
cancer, at Stage IIIb the management changes significantly because stage IIIb and stage IV patients are
unresectable. Another useful facet to lung cancer (TNM) staging is satellite nodules:
o
o
o





Same lobe = T3
Different lobe = T4
Contralateral lung = M1
For lung cancer some of the important staging features are as follows:
T1 tumours are <3cm
N1 = ipsilateral hilar nodes
T2 tumours are >3cm but >2cm from the carina
N2 = ipsilateral mediastinal or subcarinal nodes
T3 tumours are any size with extension to:
N3 = contralateral hilar, mediastinal or
supraclavicular nodes
Chest wall
Diaphgragm
Pleura or pericardium
<2cm of the carina
Satellite nodules within the same lobe
M1 = bilateral lesions, malignant pleural effusion,
distant metastases
T4 tumours affect mediastinal organs, carina, vertebral
body
T1 and T2 both have further subdivisions.
Unresectable tumours are T4, N3 or M1.
Beyond TNM staging patients with similar prognostic outcomes are given further stages. Simple
observation of these groupings reveals the following:



Stage I patients MUST be N0
Stage III patients MUST have a sum ≥ 3 (ie T2N2M0, or T1N2M0). [NB some patients with Stage II will
also have a sum of 3 (for example T2N1M0) however ALL stage III patients have a sum ≥ 3.]
Stage IIIb patients are unresectable → stage IIIb is denoted either by N3 status or T4N2.
MIDDLE EAR ANATOMY
The anatomy of the middle ear is complex but important and contains a number of specific anatomical
terms.
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The epitympanum, also known as the attic, is the superior portion above the highest point of the
tympanic membrane. It contains the head of the malleus and the short crus of the incus (These give the
appearance of an ice-cream cone on an axial CT).
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The Prussak space is found within the epitympanum and is a tiny space at the top of the tympanic
membrane, just behind the scutum. Its clinical relevance is that it is the usual origin for pars flaccida
cholesteatomas.
The aditus ad antrum connects the epitympanum to the mastoid antrum and thence the mastoid air
cells.
The tegmen mastoidium (tegmen means roof) is the point at which the mastoid air cells meet the
temporal lobe of the brain.
The tegmen tympani is the point at which the upper most extent of the epitympanum reaches the
temporal lobe of the brain.
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The mesotympanum is the space posterior to the tympanic membrane and contains the body of the
incus, the manubrium (connected to the tympanic membrane) and the anterior process of the malleus
and the stapes. The stapes is connected to the incus as well as the oval window of the cochlea. There is
also a round window placed more inferiorly which bulges to allow compression waves transmitted from
the stapes to the oval window to travel through the cochlea.
The hypotympanum is a far less significant space than either the epitympanum or the mesotympanum.
It begins at the inferior most extent of the tympanic membrane. The Eustachian tube opens into the
hypotympanum anteriorly.
This question draws on the classic differential diagnosis of ‘basal ganglia signal changes’.
Poisoning
Impairment of mitochondrial function in the highly metabolically active basal ganglia classically causes
high T2/FLAIR signal in a bilateral symmetrical fashion but the T1 is usually low in signal. Methanol,
cyanide, and carbon monoxide can all cause this.
Neurodegeneration with brain iron accumulation aka hallervorden-Spatz syndrome
The classic radiological feature which comes up here is the ‘eye of the tiger’ sign where there is low T2
signal in the globus pallidus due to iron accumulation. Confusingly the patient can go on to develop high
T2 signal in these areas as gliosis develops. The typical patient will be a young woman with a family
history of movement disorders presenting with rigidity or bradykinesia.
Behcet syndrome
Behcet syndrome is classically described as a triad of oral and genital ulcers associated with one of
several ocular manifestations. Its effect on the CNS tends to be as meningoencephalitis or venous sinus
thrombosis. In the basal ganglia, in some patients, it can cause lesions with low T1 signal and high T2
signal.
Toxoplasmosis
Infections derived from intrauterine transmission cause periventricular calcifications affecting the basal
ganglia. Otherwise, in AIDS related toxoplasmosis the findings are more of multiple ring enhancing
lesions.
Toxoplasmosis is a more common finding in AIDS patients than lymphoma is, by a large margin. On
MRI it is seen as multiple ring enhancing lesions, which can show haemorrhage particularly following
treatment. One of the stronger differentiators between toxoplasmosis and lymphoma is the SPECT
findings. This is sometimes termed ‘hypometabolic’ meaning the lesions do not demonstrate SPECT
uptake. The table below gives some general features of the two conditions. There is however
considerable overlap in the imaging features despite these broad trends.
Toxoplasmosis
Lymphoma
Number of lesions
Multiple lesions
Single lesion (can be multiple)
Predilection/involvement of
Basal ganglia
Corpus callosum
DWI
Range of appearances
Restricts
Thallium SPECT
Negative
Avid
MRS choline
Decreased
Increased
MR perfusion
Decreased rCBV
Increased rCBV
Lymphoma
A ring solitary ring enhancing lesion in the context of an AIDS patient should raise lymphoma as a
strong possibility. Multiple lesions can and do occur however, making the distinction from toxoplasmosis
challenging. Lymphoma is also part of the differential diagnosis for lesions that cross the corpus
callosum and this can be a feature that separates it from toxoplasmosis, although is not a feature of
exclusion. Similarly if haemorrhage has been seen associated with the lesion this is more a feature of
toxoplasmosis but absence of haemorrhage does not exclude toxoplasmosis.
The main features of neurofibromatosis 1 and 2 are summarised in the diagrams below:
The presence of hydrocephalus is key in this question, which should steer you away from the most
common TORCH (CMV) and towards toxoplasmosis. The key features of the TORCH infections are
below:
Toxoplasmosis
Toxoplasmosis is a reasonable suggestion if there is hydrocephalus with the calcifications.
Toxoplasmosis is the second most common TORCH infection after CMV.
CMV
This is by far the most common TORCH infection (almost twice as common as all the others put
together). Periventricular calcification is the most common finding. It is also commonly associated with
polymicrogyria.
HSV
Haemorrhagic infarction is a prominent feature of HSV, with subsequent encephalomalacia. It is usually
HSV-2 rather than HSV-1.
Rubella
Focal high signal in the white matter is the most common finding.
HIV
Frontal predominant atrophy is the main feature with basal ganglia calcification.
A superior quadrantanopia arises from a temporal lesion (Meyers loop).
An inferior quadrantanopia arises from a parietal lesion (Dorsal optic radiation).
By the time the tracts reach the occipital lobe they have rejoined and lesions of the occipital cortex
cause hemianopias, scotomas or cortical blindness.
Distinguishing between Graves eye disease and IgG4 related disease should be relatively simple.
The mnemonic for remembering the order in which the eye muscles are affected in Graves eye disease
is: I’m Slow (Inferior, Medial, Superior, Lateral). Otherwise the following table compares the features of
the two conditions.
IgG4 related disease is a relatively newly developed concept with a number of radiological avenues.
Involves ONLY muscle, not tendons or
other structures
Orbital pseudotumour aka IgG4 related
disease
Involves anything within the orbit; lacrimal
gland, tendons → any part of the eye
Unilateral or bilateral
Usually unilateral
No intraorbital fat stranding (until late)
Intraorbital fat stranding
Graves Eye Disease
Painless
Painful
Multiple associations including
retroperitoneal fibrosis
Does respond to steroids
Responds dramatically to steroids
Slow onset
Sudden onset