Anatomy of the Abdomen
in Computed Tomography
Michael C. Ficorelli, RT
Lesson Description
To explain the various exams pertaining to the
abominal cavity using computed tomography,
incorporating cross sectional anatomy from
images
Lesson Description
• To be able to identify anatomy of the abdominal
cavity. Understand the clinical indications for exams
of the abdomen. To understand the methods of
patient scanning, positioning, and protocols. To
understand indications for contrast.
CT of the Abdomen
Abdominal Cavity
• Region between the diaphragm and the sacral promontory (L-5 / S-1)
– Divided into 4 quadrants or 9 regions
• Contains:
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Liver
Gallbladder
Biliary System
Pancreas
Spleen
Adrenal Glands
Kidneys
Ureters
Stomach
Intestines
Vascular Structures
Abdominal Cavity
Peritoneum
• Thin serous membrane which lines the walls of the
abdominal cavity
– 2 Layers separated by fluid used for lubrication
• Parietal Peritoneum – lines abdominal wall
• Visceral Peritoneum – lines organs
– In males, cavity is closed. In females, cavity extends
outward via uterine tubes, uterus and vagina
– Folds extend between organs allowing them to hold
position and enclose the vessels and nerves between them
• Mesentery – encloses intestines
• Omentum – Attached to stomach
– Greater omentum – greater curvature to spleen
– Lesser omentum – lesser curvature to duodenum
Peritoneum
• Contains:
– Stomach, 1st part of duodenum, jejunum, ileum,
cecum, appendix, transverse colon, sigmoid,
upper 1/3 or rectum, liver, spleen and pancreas
• In women – fallopian tubes and ovaries
Peritoneum
• Peritoneal ligaments connect organs to one
another or to the abdominal wall
– Numerous but most important
• Falciform ligament – liver to anterior abdominal wall
and diaphragm which divides the liver into 2 lobes
Retroperitoneum
• Structures posterior to peritoneum yet lined
by it anteriorly
– Kidneys, Ureters, Adrenal Glands, Pancreas,
Duodenum, Ascending and Descending colon,
Aorta, IVC, Bladder, Prostate, and Uterus
Liver
• Largest organ in abdomen which is
divided into 4 lobes (or 8 segments
based on its vascular system) taking
up the right upper quadrant
– Left and right are largest
– Caudate – inferior and posterior
– Quadrate – inferior and anterior
• Bordered superiorly, anteriorly and
laterally by the diaphragm, medially
by the stomach and duodenum
which has many functions
– Metabolic regulation
– Hematologic regulation
– Bile production
• Has dual blood supply – arterial and
venous
Portal Hepatic System
• Route liver receives venous
blood from gastrointestinal
tract
– Portal Vein – in
retroperitoneum by union of
SMV and splenic vein
• Branches out into right and left
portal veins
• Right hepatic vein enters the
IVC laterally
• Middle hepatic vein enters
IVC anteriorly
• Left hepatic vein enters IVC
on left anterior surface
Hepatic Arterial
• Common Hepatic artery
arises from one of the 3
celiac arteries and
divides down to proper
hepatic the right and
left hepatic…
Biliary System
• Gallbladder and bile ducts
– Gallbladder is organ which
stores and concentrates bile
prior to sending to duodenum
– Bile ducts run beside hepatic
arteries and veins
• Common Bile Duct – originates
at junction of common hepatic
duct (united right and left
hepatic duct) and the cystic
duct (duct of gallbladder)
• CBD empties into the
duodenum along with
pancreatic duct at the Ampulla
of Vater through the Sphincter
of Oddi
Pancreas
• Located in retroperitoneum
• Long, narrow organ lying posterior to the stomach and
extends transversely at an oblique angle between the
duodenum and splenic hilum
– Head – broad and flat; lies nestled in the curve of the
duodenum around L – 2 / L – 3
– Body – largest anterior portion
– Tail – extends to the left anterior pararenal space
• Functions in endochrine system by producing insulin and
glucagon
– Also produces digestive enzymes
• Main pancreatic duct carries products into the duodenum
through the ampulla of vater
Pancreas
Spleen and Adrenal Glands
• Spleen – in peritoneum, posterior to the
stomach; largest lymph organ which functions to
produce white blood cells, remove abnormal
blood cells, and aid in immunity
• Adrenal Glands – located superior to each kidney
– Right is located just posterior to IVC, medial to the
posterior part of the right hepatic lobe – lower and
more medial than the left
– Left is triangular shaped
• Both produce more than 2 dozen hormones including
corticosteroids
Spleen and Adrenal Glands
Kidneys
• Bean shaped organs lying obliquely on the posterior
abdominal wall on either side of the vertebral column,
contains medial hilum where renal arteries and veins enter
– Gerota’s (Renal) Fascia – protective layer anchoring the kidneys
to the surrounding structures
– Renal Cortex – outer third containing the nephrons (functional
unit of kidney)
– Renal Medulla – consists of renal pyramids which contain the
loops of Henle (beginning of collecting system)
– Renal Pelvis - kidney has 7-14 minor calyces which merge into 2
– 3 major calyces…they merge together to form renal pelvis
• Largest point of collecting system which is continuous with the ureter
• Filters blood of impurities and begins transportation out
Kidneys
• Ureters – muscular
tubes transporting
urine to the urinary
bladder in the pelvis
Stomach
• Located under left dome of
diaphragm and responsible
for early digestion
• 3 Parts
– Fundus – superior
• Entry is through cardiac orifice
– Body – largest
• 2 curves – Lesser and Greater
– Pylorus – empties into
duodenum through pyloric
sphincter
• Rugae – prominent folds
when stomach is empty
Small Intestine
• Loops of bowel approx. 6 –
7 meters in length
• 3 portions
– Duodenum – short, begins
following pylorus and curves
around head of pancreas
• Bulb – 1st 2 inches
– Jejunum – 2.5 meters long,
bulk of digestion occurs here
– Ileum – Lower 3/5, longest
portion
• Ileocecal Valve – termination
of small bowel
Large Intestine
• Functions to reabsorb water
and excrete feces
• 1.5 meters in length, “Frames”
the small intestine, large
diameter and thinner walls
– Taenia coli – bands which form
the haustra pockets
• Parts:
– Cecum – at ileocecal valve
• Veriform appendix – attached to
cecum
– Colon:
• Ascending – On right
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Hepatic flexure
Transverse
Splenic flexure
Descending
Sigmoid
Rectum
Abdominal Aorta
• Located in retroperitoneum
• Extension of thoracic aorta through the
diaphragm and descends just left of the
midline next to vertebrae
• At L-4, Bifurcates into the common iliac
arteries
Abdominal Aorta
• Branches in order descending…
– Inferior Phrenic – Paired
– Celiac Trunk – divides into left gastric, common
hepatic and splenic arteries
– Superior Mesenteric Artery (SMA) – Level L-1 – feeds
pancreas and both small and large intestines
– Suprarenal
– Renal – L-1 / L-2
– Gonadal
– Inferior Mesenteric Artery (IMA) – Level L-3/4
Abdominal Aorta
Inferior Vena Cava
• Largest vein in the body carrying blood from the
lower limbs, pelvis, abdominal viscera and wall
• Formed by union of common iliac veins at level
of L-5
• Passes through posterior surface of the liver and
ascends through the diaphragm to the heart
• Has tributaries:
– Renal Veins – IVC at L-2
– Hepatic Veins – IVC at level of diaphragm
Visualized Abdominal Muscles
• Psoas Muscle – extends along lateral surfaces
of the lumbar vertebrae
• Rectus abdominus – anterior surface of the
abdomen and pelvis
– Linea Alba – longitudinal band of fibers found at
midline anteriorly
• External and Internal Oblique – outer lateral
portions of the abdomen until crest
Indications for Abdominal Imaging
• Metastatic Workup
• Abscess
• Abdominal Pain
– Presenting Right Lower Quadrant Pain – Appendicitis?
– Presenting Left Lower Quadrant Pain – Diverticulitis?
– Presenting Flank or Lower Back Pain – Renal Colic?
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Liver Function and Structure
Pancreatic Pathologies
Hernia – Hiatal means Chest!
Aneurysm of Abdominal Aorta
Patient Preparation
• If exam is done with I.V. contrast patient must be
NPO 4-6 hours
• Lab work for I.V. contrast exams
• Oral contrast can be given the night before and the
morning of the exam, or can be given 2 hours before
the exam
• Oral contrast can be given at a constant rate of
900ml over a 45 minute period, 200ml is given at the
time of the exam to distend the stomach
• Air contrast can also be used to give a negative
(black) appearance
Parameters
PATIENT
Single Slice
4 SLICE
FEET FIRST. SUPINE
SAME
SAME
ABOVE LIVER TO SYMPHSIS
SAME
SAME
• Lung nodules
PUBIS
100ML AT 2-3 ML/SEC @ 45SAME
CONTRAST
• Cancer
80 SECOND DELAY
NA
4X2.5MM
DETECTOR COLLI
• Vascular disease
ON PATIENT
SAME
DFOV
• Effusion andDEPENDS
infiltration
5 MM
SAME OR SMALLER
SLICE THICKNESS
• Trauma
SAME
ANGLE
• Pulmonary NONE
Parenchymal diseases
6MM
12.5MM
TABLE FEED/ROT
• Hilar Masses
SCANNING AREA
16 SLICE
SAME
16X1.5
SAME
SAME
SAME
24MM
PITCH
1 OR 1.5
VARIES
VARIES
ROT TIME
1 SEC
0.5 SEC
0.5 SEC
RECON
STANDARD/LIVER IF NO I.V.
CONTRAST
SAME
SAME
WINDOW
450W/30L
SAME
SAME
Abdomen CT
2
1
3
1 – Liver
2 – Rt. Venticle
3 – Lt. Ventricle
4 – IVC
5 – Azygos Vein
6 - Abdominal Aorta
6
4
5
7
7 – Rt. Atrium
Abdomen CT
1
2
3
1 – Rt Hepatic Vein
2 – Middle Hepatic
Vein
3 – Left Hepatic
Vein
4 - IVC
4
Abdomen CT
2
1
1 – Middle Hepatic
Vein
3
2 – Left Hepatic
Vein
3 – Stomach
6
4 – Right Hepatic
Vein
5 – Caudate Lobe
of Liver
4
5
1 – Lt. Portal Vein
Abdomen CT
1
3
2
2 – Portal Vein
3 – Falciform
Ligament
4
4 – Celiac Artery
9
5 – IVC
6 – Lt Kidney
8
7 - Splenic Artery
8 – Spleen
7
9 – Splenic Flexure
6
10 – Adrenal Gland
5
10
Abdomen CT
3
1 – Rt Adrenal
2 – Pancreas
3 - SMA
2
1
Abdomen CT
2
1
3
6
1 - Duodenum
2 – Duodenal
Bulb
3 – Pylorus
4 – Left Renal
Vein
5
5 – Pancreas
6 - SMA
4
Abdomen CT
5
1
2
1 – Transverse
Colon
2 – SMA
3
3 - Small Intestine
(Jejunum)
4 – Renal Artery
5 – SMV
4
Abdomen CT
1
2
3
1 – Hepatic Flexure
(Ascending Colon)
2 – Transverse
Colon
3 – Descending
Colon
Abdomen CT
1
2
3
4
1 – IVC
2 – Linea Aspera
3 – Rectus
Abdominus
4 – Aorta
5 - Psoas
5
Phasic Studies of Liver
A three phase CT scan, usually of the liver, requires an
injection of contrast medium which helps outline the
vessels of your body by giving the x-rays something to be
absorbed by besides blood which has a very low
absorption rate. The phases are:
1. Scan during injection: Arterial Phase, this will highlight
lesions in or around the artery leading into the liver.
2. Scan during injection or shortly after: Portal Venous
Phase, this will show lesions in or around the portal vein.
3. Delayed scan after injection: Equilibrium Phase, this
will allow the soft tissue to absorb the contrast and may
highlight changes in tissue.
Parameters
Single Slice
4 SLICE
16 SLICE
PATIENT
FEET FIRST. SUPINE
SAME
SAME
SCANNING AREA
ABOVE LIVER TO SYMPHSIS
PUBIS OR ASIS
SAME
SAME
CONTRAST
100-150ML @ 2 -4 CC/SEC
PHASE 1 – NON CONTRAST
PHASE 2 – 30 SECONDS
PHASE 3 - 70 SECONDS
SAME
SAME
DETECTOR COLLI
NA
4X1MM 4X1.25
16X.075 16X1.25
DFOV
DEPENDS ON PATIENT
SAME
SAME
SLICE THICKNESS
5 MM
1-5 MM
SAME
ANGLE
NONE
SAME
SAME
TABLE FEED/ROT
4MM
VARIES
VARIES
PITCH
1.5
VARIES
VARIES
ROT TIME
1 SEC
0.5 SEC
0.5 SEC
RECON
STANDARD
SAME
SAME
WINDOW
450W/30L
SAME
SAME
Phasic Studies of Liver
CT Urography
• Test of choice for many urologic problems,
including urolithiasis, renal masses, urinary tract
infection, trauma, and obstructive uropathy.
• CT urography provides a detailed anatomic
depiction of each of the major portions of the
urinary tract--the kidneys, intrarenal collecting
systems, ureters, and bladder--and thus allows
patients with hematuria to be evaluated
comprehensively.
CT Urography