Pneumothorax
Dr Andrew Dixon◉ and Dr Martin Gorrochategui et al.
Pneumothorax (PTX) (plural: pneumothoraces) refers to the presence of gas (air) in the pleural space. When this collection of gas is constantly
enlarging with resulting compression of mediastinal structures, it can be life-threatening and is known as a tension pneumothorax (if no tension is
present it is a simple pneumothorax). For those pneumothoraces occurring in neonates see the article on neonatal pneumothorax.
Epidemiology
There are many causes of pneumothorax which makes it impossible to generalise the epidemiology. However, primary spontaneous
pneumothoraces occur in younger patients (typically less than 35 years of age) whereas secondary spontaneous pneumothoraces occur in older
patients (typically over 45 years of age) 4.
Clinical presentation
Presentation is variable and may range from no symptoms to severe dyspnoea with tachycardia and hypotension. In patients who have a tension
pneumothorax, presentation may be with distended neck veins and tracheal deviation, cardiac arrest and in the most severe cases, death.
It is interesting to note that some generalisations can be made in regards to the clinical presentation in primary versus secondary spontaneous
pneumothoraces:

primary spontaneous: pleuritic chest pain usually present, dyspnoea mild or moderate

secondary spontaneous: pleuritic chest pain often absent, dyspnoea usually severe
Pathology
It is useful to divide pneumothoraces into three categories 4:

primary spontaneous: no underlying lung disease

secondary spontaneous: underlying lung disease is present

iatrogenic/traumatic
Primary spontaneous
A primary spontaneous pneumothorax is one which occurs in a patient with no known underlying lung disease. Tall and thin people are more likely to
develop a primary spontaneous pneumothorax. There may be a familial component, and there are well-known associations 10:

Marfan syndrome

Ehlers-Danlos syndrome

alpha-1-antitrypsin deficiency

homocystinuria
Secondary spontaneous
When the underlying lung is abnormal, a pneumothorax is referred to as secondary spontaneous. There are many pulmonary diseases which
predispose to pneumothorax including:

cystic lung disease
o
o
o
o
o
o
o
o

bullae, blebs
emphysema, asthma
pneumocystis jiroveci pneumonia (PJP)
honeycombing: end-stage interstitial lung disease
lymphangiomyomatosis (LAM)
Langerhans cell histiocytosis (LCH)
due to apical lung changes from ankylosing spondylitis 1
cystic fibrosis
parenchymal necrosis
o
o
lung abscess, necrotic pneumonia, septic emboli, fungal disease, tuberculosis
cavitating neoplasm, metastatic osteogenic sarcoma
o
o

radiation necrosis
pulmonary infarction
other
o
catamenial pneumothorax 2,4: recurrent spontaneous pneumothorax during menstruation, associated with endometriosis of
pleura
o
rarely pleuroparenchymal fibroelastosis
9
Iatrogenic/traumatic
Iatrogenic/traumatic causes include 1-4:

iatrogenic:
o
o
o
o
o

percutaneous biopsy
barotrauma (e.g. divers), ventilator
radiofrequency (RF) ablation of lung mass
endoscopic perforation of the oesophagus
central venous catheter insertion, nasogastric tube placement
trauma:
o
o
o
o
pulmonary laceration
tracheobronchial rupture
acupuncture 14,15
oesophageal rupture
Others

pneumoperitoneum with passage through congenital/acquired diaphragmatic defects

buffalo pneumothorax is the presence of bilateral pneumothoraces due to an abnormal communication between the pleural spaces
Unusual forms

loculated pneumothorax

interlobar pneumothorax / interfissural pneumothorax 17 - form of loculated pneumothorax confined to the fissures
Radiographic features
Plain radiograph
A pneumothorax is, when looked for, usually easily appreciated on erect chest radiographs. Typically they demonstrate:

visible visceral pleural edge is seen as a very thin, sharp white line

no lung markings are seen peripheral to this line

peripheral space is radiolucent compared to the adjacent lung

lung may completely collapse

mediastinum should not shift away from the pneumothorax unless a tension pneumothorax is present (discussed separately)

subcutaneous emphysema and pneumomediastinum may also be present
Described methods for estimating the percentage volume of a pneumothorax from an erect PA radiograph include:

Collins method 19
o
o
o
o

% = 4.2 + 4.7 (A + B + C)
A is the maximum apical interpleural distance
B is the interpleural distance at midpoint of upper half of lung
C is the interpleural distance at midpoint of lower half of lung
Rhea method 20

Light index 21
In cases where a pneumothorax is not clearly present on standard frontal chest radiography a number of techniques can be employed:

lateral decubitus radiograph:
o
o

should be done with the suspected side up
the lung will then 'fall' away from the chest wall
expiratory chest radiograph:
o
o
lung becomes smaller and denser
pneumothorax remains the same size and is thus more conspicuous: although some authors suggest that there is no difference
in detection rate 6

CT scan
When imaged supine detection can be difficult: see pneumothorax in a supine patient, and pneumothorax is one cause of a transradiant hemithorax.
Ultrasound
M-mode can be used to determine movement of the lung within the rib-interspace. Small pneumothoraces are best appreciated anteriorly in the
supine position (gas rises) whereas large pneumothoraces are appreciated laterally in the mid-axillary line.
See: ultrasound for pneumothorax.
CT
Provided lung windows are examined, a pneumothorax is very easily identified on CT, and should pose essentially no diagnostic difficulty. When
bullous disease is present, a loculated pneumothorax may appear similar.
Treatment and prognosis
Treatment depends on a number of factors:

size of the pneumothorax

symptoms

background lung disease/respiratory reserve
Estimating the size of pneumothorax is somewhat controversial with no international consensus. CT is considered more accurate than plain
radiograph.

British Thoracic Society (BTS) guidelines (2010): measured from chest wall to lung edge at the level of the hilum
o
o

12
<2 cm: small
≥2 cm: large
American College of Chest Physicians guidelines (2001): measured from thoracic cupola to lung apex 13
o
o
<3 cm: small
≥3 cm: large
These can be used together to determine the best course of action. The following is based on the BTS guidelines 12 for the treatment of
pneumothorax; local protocols may differ:

asymptomatic small rim pneumothorax: no treatment with follow-up radiology to confirm resolution

pneumothorax with mild symptoms (no underlying lung condition): needle aspiration in the first instance

pneumothorax in a patient with background chronic lung disease or significant symptoms: intercostal drain insertion (small drain using
the Seldinger technique)
In trauma patients, the "35 mm rule" seems to predict which patients can be safely observed. If the pneumothorax measures <35 mm, when
measuring the largest air pocket between the parietal and visceral pleura perpendicular to the chest well on axial imaging, in stable, non-intubated
patients there was a 10% failure rate (i.e. requiring intercostal catheter insertion) during the first week 16.
In patients with recurrent pneumothoraces or who are at very high risk of having recurrent events and have a poor respiratory reserve, pleurodesis
can be performed. This can either be medical (e.g. talc poudrage) or surgical (e.g. VATS pleurectomy, pleural abrasion, sclerosing agent) 4.
Differential diagnosis
Usually, the diagnosis is straightforward, but occasionally other entities should be considered:

artifacts: air caught between structures outside the chest
o
skinfold:

the apparent pleural edge is denser (i.e. black) compared to a true pneumothorax which is a white pleural edge

o
o
may be seen extending beyond the chest cavity or seen to fade out
clothing
blankets

monitoring leads (although these should be obvious)

overlapping breast margin

normal anatomical structures, e.g. medial border of the scapula

pulmonary bullae

giant bullous emphysema: differentiated from tension pneumothorax by clinical stability, interstitial vascular markings projected with the
bullae and lack of hemithorax re-expansion following the insertion of an intercostal catheter

calcified pleural plaques

other gas in abnormal locations
o
o
pneumomediastinum
pneumopericardium

other causes of a hyperlucent hemithorax

on CT
o
o
gas in a brachiocephalic vein from cannulation
beam-hardening artifact from concentrated iodinated contrast in a brachiocephalic vein or the SVC
See also

pneumothorax ex vacuo

tension pneumothorax

pneumothorax (basic)

capnothorax
Pneumomediastinum
Dr Tom Foster and Dr Martin Gorrochategui et al.
Pneumomediastinum is the presence of extraluminal gas within the mediastinum. Gas may originate from the lungs, trachea, central
bronchi, oesophagus, and peritoneal cavity and track from the mediastinum to the neck or abdomen.
Terminology
In the setting of trauma, if pneumomediastinum is visible on chest x-ray it is termed overt pneumomediastinum whereas if it is only visible on CT
then it is termed occult pneumomediastinum 8.
Pathology
Aetiology

blunt or penetrating chest trauma

secondary to neck, thoracic, or retroperitoneal surgery

oesophageal perforation
o
o
o


laceration
bronchial stump dehiscence
bronchoscopy
tracheostomy
laryngeal fracture
childbirth (see: Hamman syndrome)
weightlifting
Valsalva manoeuvre
asthma
barotrauma
o
o

oesophageal carcinoma
vigorous exercise (see: pulmonary interstitial emphysema)
o
o
o

endoscopic intervention
tracheobronchial perforation
o
o
o
o
o

Boerhaave syndrome
diving
ventilator: most commonly secondary to ARDS with positive pressure ventilation
infection
o
o
o
o
tuberculosis
histoplasmosis
dental or retropharyngeal infection
mediastinitis

interstitial lung disease 12

connective tissue disorders
o

11
polymyositis/dermatomyositis, uncertain if related to vasculopathy or associated interstitial lung disease 12
idiopathic
Although it is rare, pneumomediastinum can occur spontaneously. This is considered benign and generally affects young adult males 9,10.
Radiographic features
Small amounts of gas appear as linear or curvilinear lucencies outlining mediastinal contours such as:

subcutaneous emphysema

gas anterior to pericardium: pneumopericardium

gas around pulmonary artery and main branches: ring around artery sign

gas outlining major aortic branches: tubular artery sign

gas outlining bronchial wall: double bronchial wall sign

continuous diaphragm sign: due to gas trapped posterior to pericardium

gas between parietal pleura and diaphragm: extrapleural sign

gas in pulmonary ligament

Naclerios V sign
Paediatric pneumomediastinum may have slightly different appearances:

elevated thymus: thymic wing sign

gas crossing the superior mediastinum: haystack sign (the heart appears like a haystack in a Monet painting)
Ultrasound
Sonography is not a diagnostic modality of choice, but is often used in the initial workup of undifferentiated trauma patients, or in differentiating
causes of dyspnoea or chest pain. Sonographic features which may appear in pneumomediastinum include 14:

cervical subcutaneous emphysema
o
o

typically found anterior or lateral to the thyroid and medial to the internal jugular vein
loss of the parasternal and apical views when performing transthoracic echocardiography
o

anterior cervical ultrasonography demonstrates hyperechoic foci with "dirty" posterior acoustic shadowing
with preservation of the subxiphoid window
the air gap sign
o
o
originally described using M-mode, describes systolic obscuration of cardiac structures as viewed from a parasternal long axis view 15
cyclic appearance of a dense band of horizontal reverberation artifacts which were discontinuous in the far field
Differential diagnosis
Must be distinguished most importantly from:

medial pneumothorax

pneumopericardium

pneumoperitoneum

pneumoretroperitoneum

Mach bands

subcutaneous emphysema
For small gas collections on a CT scan, also consider 3:

subcarinal air cyst

paratracheal air cyst

tracheal diverticulum
Aortic aneurysm
Dr Yair Glick◉ and Assoc Prof Craig Hacking◉ ◈ et al.
The broad term aortic aneurysm is usually reserved for pathology discussion. More specific anatomic and radiologic discussion is based on the
location of the aneurysm:

thoracic aortic aneurysm

abdominal aortic aneurysm
Related Radiopaedia articles
Aortic pathology

acute aortic syndrome[+]

aortic aneurysms
o
o
o
o
thoracic aortic aneurysm

aortic root dilatation[+]

ascending aorta dilatation

thoracic aortic dilatation (differential)
abdominal aortic aneurysm

aortic aneurysmal rupture

aorto-caval fistula

aorto-enteric fistula

aorto-left renal vein fistula

inflammatory abdominal aortic aneurysm[+]

signs[+]
endovascular aneurysm repair (EVAR)
reporting tips for aortic aneurysms

inflammatory[+]

congenital[+]

traumatic aortic injury[+]

miscellaneous[+]
PEDIATRIC RADIOLOGY
1. Hirschsprung
Disease
- the most common cause of neonatal colonic obstruction (15-20%). It is commonly characterised by a short segment of colonic aganglionosis
affecting term neonates, especially boys.
S/Sx:
- typically presents in term neonates with failure to pass meconium in the first 1-2 days after birth, although later presentation is also common.
- ~75% of cases present within six weeks of birth
- over 90% of cases present within the first five years of life
- A very small number may present in the adult population
Dx:
A definitive diagnosis requires a full thickness rectal biopsy.
Pathology:
- characterised by aganglionosis (absence of ganglion cells) in the distal colon and rectum
- failure of neuroblasts in neural crest cells to migrate into bowel segments or degeneration of already migrated neuroblasts
- affects cells both in the myenteric and submucosal plexuses
- functional obstruction develops as a result of a spasm in the denervated colon
It can be anatomically divided into four types according to the length of the aganglionic segment:

short segment disease: ~75% *
o

long segment: ~15%
o

typically extends to splenic flexure / transverse colon
total colonic aganglionosis: ~7.5% (range 2-13%)
o
o

rectal and distal sigmoid colonic involvement only
also known as Zuezler-Wilson syndrome
occasional extension of aganglionosis into the small bowel
ultrashort segment disease
o
o
3-4 cm of internal anal sphincter only
controversial entity
Radiographic features:
Radiograph
Fluoroscopy
Antenatal ultrasound
Tx/ Prognosis:
Surgical treatment is by removal of the affected portion of the colon
Differential diagnosis:
General differential considerations include
 functional megarectum
 necrotising enterocolitis
 microcolon: appears similar to long segment / whole colon Hirschsprung disease
2. Pyloric
stenosis
- the idiopathic thickening of gastric pyloric musculature which then results in progressive gastric outlet obstruction.
Risk factors
 being firstborn
 maternal history of pyloric stenosis
S/Sx:
- symptoms may start as early as 3 weeks, it typically clinically manifests between 6 to 12 weeks of age.
- non-bilious projectile vomiting.
- olive-sized mass in the right upper quadrant
- succussion splash may be audible
- Due to the loss of hydrochloric acid in the gastric contents from persistent vomiting, patients are at risk of electrolyte imbalance, specifically
the characteristic hypochloraemic metabolic alkalosis.
Pathology:
- result of both hyperplasia and hypertrophy of the pyloric circular muscle fibers
Dx:
Ultrasound is the modality of choice in the right clinical setting because of its advantages over a barium meal are that it directly visualises the
pyloric muscle and does not use ionising radiation.
The hypertrophied muscle is hypoechoic, and the central mucosa is hyperechoic. Diagnostic measurements include (mnemonic "number pi"):
 pyloric muscle thickness, i.e. diameter of a single muscular wall (hypoechoic component) on a transverse image: >3 mm (most accurate 3)
 length, i.e. longitudinal measurement: >15-17 mm
 pyloric volume: >1.5 cm3
 pyloric transverse diameter: >13 mm
With the patient's right side down the pylorus should be watched and should not be seen to open.
Described sonographic signs include:
 antral nipple sign
 cervix sign
 target sign
Tx:
Treatment is surgical with a pyloromyotomy in which the pyloric muscle is divided down to the submucosa. This can be performed both open and
laparoscopically.
3. Primary Pulmonary Tuberculosis
- patients not previously exposed to Mycobacterium tuberculosis
- most common in infants and children and has the highest prevalence in children under 5 years of age
Radiographic features
Primary pulmonary tuberculosis manifests as four main entities:
 parenchymal disease
o usually manifests as dense, homogeneous parenchymal consolidation in any lobe
o however, predominance in the lower and middle lobes (subpleural sites) is suggestive of the disease, especially in adults
 lymphadenopathy
 miliary opacities
 clustered parenchymal opacification may give a galaxy sign
 pleural effusion
1
Treatment and prognosis
- parenchymal focus resolves without sequelae at conventional radiography
- this resolution can take up to 2 years. In the remaining cases, a radiologic scar persists that can calcify in up to 15% of cases, an entity
that is known as a Ghon focus.
Differential diagnosis
- indistinguishable from that of bacterial pneumonia.
4. Wilms Tumour
- also known as nephroblastoma, is a malignant paediatric renal tumour.
- most common paediatric renal mass, accounting for over 85% of cases 1,8 and accounts for 6% of all childhood cancers
S/Sx:
- painless upper quadrant abdominal mass
- Haematuria is seen in ~20% of cases
- hypertension due to excessive renin production
Radiographic features
- large heterogeneous solid masses which displace adjacent structures. Occasionally they may be mostly cystic.
5. Patent Urachus
- occasionally been termed "urachal fistula"
- urine is noted leaking from the umbilicus
Pathology:
- failure of the entire course of the fetal allantois to involute into the median umbilical ligament
- results in an open channel between the bladder and the umbilicus
Radiographic features
Contrast studies (VCUG)
A patent urachus can be demonstrated by:
 retrograde injection of contrast material into the orifice of the channel at the umbilical end
 reflux up the urachus during VCUG (better seen in the lateral projection)
Ultrasound
A patent urachus can be seen on longitudinal ultrasound images of the midline ventral abdomen as a tubular connection between the
anterosuperior aspect of the bladder and the umbilicus.
6. Congenital Heart Disease
I. Most important congenital heart defects associated with cyanosis :





T:
T:
T:
T:
T:
tetralogy of Fallot (TOF)
transposition of the great arteries (TGA)
truncus arteriosus
total anomalous pulmonary venous return (TAPVR)
tricuspid valve abnormalities and hypoplastic right heart syndrome
GI RADIOLOGY
Acute Appendicitis
Acute Pancreatitis
Malignant vs Benign Ulcer
Colorectal Carcinoma
Intestinal Volvulus
Ascending Cholangitis
1. Acute Appendicitis
inflammation of the vermiform appendix
- one of the main reasons for abdominal surgery in young patients
-
 CT is the most sensitive modality to detect appendicitis.
- a disease of children and young adults with a peak incidence in the 2nd to 3rd decades of
life
S/Sx:
- periumbilical pain (referred) which within a day or later localizes to McBurney point with
associated fever, nausea and vomiting
- children often present with vague and non-specific signs and symptoms
General signs and symptoms include 1,2:
 fever
 localized pain and tenderness
o right lower quadrant pain over appendix (i.e. McBurney sign)
o pelvic pain, diarrhea and tenesmus (pelvic appendix)
o flank pain (retrocecal appendix)
o groin pain - appendix within an inguinal hernia (Amyand hernia) or a femoral hernia
(De Garengeot hernia)
o right upper quadrant pain (subhepatic appendicitis )22
 leukocytosis
 nausea and vomiting
 atypical location:
o within the pelvis (30%)
o extraperitoneal (5%)
o left iliac fossa (rare), found in patients with a long appendix, intestinal malrotation,
situs inversus and those with a mobile cecum
 Alvarado Score
 PAS or pARC Score for Pedia
Pathology:
Obstruction may be caused by 1:
 lymphoid hyperplasia (~60%)
 appendicolith (~33%)


foreign bodies (~4%)
Crohn disease or other rare causes, e.g. stricture, tumor, parasite