CT of the
Hepatobiliary System
and Pancreas
Kelly Pollak, MS3
Module Outline

Part I: Liver Parenchyma

Part II: Biliary Tract

Part III: Gallbladder

Part IV: Pancreas
Part I:
Liver Parenchyma
CT of the Liver
Normal Anatomy (as seen on un-enhanced CT):

Hepatic parenchyma high density (liver > spleen
> muscle)

Homogenous appearance of parenchyma

Hepatic veins and portal veins branch through
parenchyma as lower density structures
Hepatic Anatomy – Segments




The liver is composed of right and left lobes (separated
anatomically by a vertical plane through the IVC, gallbladder fossa,
and middle hepatic vein), and a total of 8 segments, which are
divided by main hepatic veins and portal veins (inferiorly)
Each segment has its own vascular supply and biliary drainage
The segments are numbered clockwise when the liver is viewed
ventrally
It is useful to learn the individual segment locations on CT in order
to localize masses
Hepatic Segments as seen on CT

Superior liver: Left, middle, and
right hepatic veins (arrows)
can be used to demark
segments II, IV, VII, and VIII,
and the IVC can be used to
locate I (which lies next to it) :

Inferior liver: Fissure for
falciform ligament appears
(block arrow) and the left,
middle, and right hepatic veins
(black arrows) now can be
used to demark segments III,
IV, V, VI:
Role of intravenous contrast in liver
CT

Increases the density of normal liver
parenchyma

Emphasizes difference between parenchyma
and poorly enhancing lesions

Scans at different time intervals after contrast
administration allow visualization of different
phases of opacification, enabling distinction of
lesions such as hemangiomas and neoplasms
IV Contrast Distribution Over Time

Three phases of hepatic enhancement post-contrast
injection:



Vascular: Rapid rise in aortic enhancement and gradual hepatic
enhancement
Redistribution: Contrast diffuses from central blood
compartment to extravascular liver compartment (increase in
hepatic enhancement and decrease in aortic)
Equilibrium: Aortic and hepatic enhancement gradually decline
as contrast diffuses back into central vascular compartment and
to muscle and fat compartments
Normal liver, unenhanced CT
Note the areas of hypodensity (arrows), which are normal hepatic and
portal veins coursing through the liver.
Photo, Armstrong et al, 2004
Normal liver CT, enhanced
Note the increased density of the hepatic and portal veins. Also note
the adjacent stomach, which is filled with contrast.
Photo, Armstrong et al. 2004
Systematic Approach to Examining
Liver Parenchyma

Observe for:
 Overall shape
 Should have smooth edges
 cirrhosis
 Homogeneity of parenchyma
 Parenchyma should be homogenous. This helps in
determining:





Liver metastases
Primary tumors
Abscesses
Cysts
Trauma
Shape

Normal liver edges
should be smooth:

In Cirrhosis, liver
edges have a nodular
contour:
Photo Lee et al, 1998
L=liver, C=caudate lobe
Homogeneity: Primary Benign Liver
Masses

Contrast enhancement helps determine
presence of hemangiomas:
 In
early vascular phase, hemangiomas are
lower density than surrounding parenchyma
 During
later phases, hemangiomas appear
higher density than surrounding parenchyma
CT Detection of Hemangioma
Early arterial phase
Photos, Armstrong et al, 2004
Later (redistribution)
phase
Homogeneity – Hepatic Neoplasms
Contrast enhancement also helps identify
hepatic neoplasms:
Neoplasms, both metastases and primary
neoplasms, can be hyper- or hypovascular.
Hypervascular enhance brightly during
early arterial phase, whereas hypovascular
are hypodense in the early arterial phase
(but enhance during the redistribution
phase).
Homogeneity – Hepatic Neoplasms

Knowing which lesions are hypervascular and
which are hypovascular can help identify the type
of neoplasm, but the key thing is that they are of a
different density than the surrounding liver
parenchyma.
 Hypervascular
examples: carcinoid tumor mets,
hepatocellular carcinoma
 Hypovascular examples: colon cancer mets,
cholangiocarcinoma

Most mets, as opposed to primary tumors, are
rounded and well demarcated from surrounding
parenchyma on enhanced scans.
Appearance of various liver neoplasms
during early arterial phase
Hypovascular metastasis
due to colon cancer
Carcinoid tumor metastasis
is hypervascular
Hypovascular primary
cholangiocarcinoma
Primary hepatocellular
carcinoma is hypervascular
(hypodense area is necrosis)
Homogeneity – Cysts and
Abscesses
Contrast also helps identify cysts and abscesses, which
contain collections of fluid

Cysts: Have well-defined margins and are low density
(attenuation similar to water), unenhancing lesions


Note: cysts below ~ 1cm in size cannot be reliably distinguished
from neoplasms
Abscesses: appear similar to cysts, but usually their
walls are thicker (due to surrounding edema) and more
irregular

May not be able to distinguish from a necrotic tumor
Hepatic Cyst vs. Abscess
Photo, Novelline et al, 2004
Photo Lee et al, 1998
Left, hepatic cyst; right, hepatic abscess. Note the thickened wall of
the abscess.
Homogeneity – Liver Trauma

Trauma can cause hepatic parenchymal
lacerations, subcapsular and intrahepatic
hematomas

All are low-density areas relative to contrastenhanced parenchyma

Leakage of contrast = active bleeding
Hepatic Laceration
Photo, www.e-radiography.net
Quiz time
Identify and localize the following
liver abnormalities on CT
What is the abnormality, and what
segment is it located in?
Answer
There is hepatocellular carcinoma in the second segment
of the liver. Notice how it enhances here during an early
arterial phase scan (hypervascular) and is less well
defined than metastases would appear.
What is the abnormality?
Answer
This represents cirrhosis of the liver. Note the nodular appearance of
the liver, instead of the usual smooth edges characteristic of a normal,
healthy liver.
What is the abnormality, and in
what segment is it located?
Image, www.learningradiology.com
Answer

There is a laceration
from a traumatic
injury to the liver,
located in segment
VII.
Part II:
Biliary Tract CT
Normal Anatomy








Bile (green tract in image) flows thru
biliary tree from periphery of liver to
duodenum
Biliary tree: intrahepatic ducts,
common hepatic duct (CHD), and
common bile duct (CBD)
Intrahepatic ducts course from
periphery centrally to hepatic hilum
Join to form centrally located main left
and right hepatic ducts
Portal triad: intrahepatic ducts are
located adjacent to portal veins and
hepatic arteries
Left and right hepatic ducts join to form
common hepatic duct near liver margin
Porta Hepatis – CHD runs with portal
vein and hepatic artery
CHD joins cystic duct to form CBD
inferior to the liver
Appearance on CT

Superior slices: With contrast,
intrahepatic ducts appear as
hypodense areas in the periphery
of the parenchyma (look very
closely to see); they appear near
portal veins and hepatic arteries,
which enhance.

More inferior slices: As move
inferiorly, right and left hepatic
ducts appear centrally
(hypodensities, arrows), adjacent
to the right and left portal veins
(brightly enhancing, block arrows).
Appearance on CT, cont’d.


Further inferiorly: The left
and right main hepatic ducts
fuse to form the common
hepatic duct, and the left and
right portal veins fuse to form
the portal vein.
Common
hepatic duct
forming
Portal vein
forming
Even more inferior:
Common hepatic duct (and
porta hepatis) appears.
CHD
Hepatic
artery
Portal
vein
Appearance on CT, cont’d.

Most inferior:
Gallbladder appears,
left lobe of liver starts
to disappear
Click through the following
slides to familiarize yourself
with the progression of the
biliary system superior-toinferior within the liver
Systematic Approach to Examining
Biliary Tract on CT

Things to look at:
 Bile
duct size
Peripheral ducts: mean diameter=1.8mm
 Central ducts: mean diameter=2mm
 Common hepatic duct: mean diameter=2.8mm

 Bile
duct wall
Wall enhances to varying degrees with IV contrast
(insensitive indicator of pathology)
 Thickness important; normal 1-1.5mm

 Density

Normal is near water density
Abnormalities – Biliary Dilatation

Dilated biliary ducts are a
feature of biliary
obstruction, common
causes of which include:



Impacted stone in CBD
Carcinoma in head of
pancreas
Carcinoma in ampulla of
Vater
Note the greatly enlarged
intrahepatic bile ducts. As
expected, they are hypodense
compared to the liver
parenchyma.
Photo Armstrong et al, 2004
Part III
Gallbladder
Gallbladder Anatomy



Gallbladder is a storage
organ
It is located within the
gallbladder fossa of the
liver, which separates the
right and left lobes of the
liver
Its wall is normally thin,
and it is usually filled with
bile
Gallbladder Appearance on CT



Sits in fossa between
right and left lobes of
liver
Density: fluid density,
free of particulate
debris
Usually distended
with bile
Systematic Approach to Observing
Gallbladder on CT
Observe for three things: size, density, and
surroundings:
 Size:


Overall size: Diameter 2-5cm
Wall size: 3mm thickness

Density: Homogenous, fluid density

Surroundings: No surrounding edema should be
present
Abnormalities – Acute Cholecystitis

Size: distended gallbladder,
possibly thickened wall,
subserosal edema. CHD or CBD
may be dilated if they are
occluded.

Density: gallstones may be
visible (usually hyperintense
spots); high density bile

Surroundings: pericholecystic
stranding and fluid (indicating
inflammation)
Notice the thickened gallbladder wall
(arrowheads) and dilated CHD.
Photo Lee et al, 1998
Abnormalities – Chronic Cholecystitis

Size:

Small, irregularly shaped
overall
 Wall: dystrophic
calcification (aka,
Porcelain Gallbladder)
 CHD or CBD may be
dilated if they are
occluded

Density:

Bile w/particulate matter
and high concentration of
calcium cmpds appears
radio-opaque (aka, Milk of
Calcium Bile)
Notice the rim of enhancement
around the gallbladder, indicating
calcification.
Photo Novelline RA, 2004

Abnormalities – Gallbladder
Carcinoma
Major manifestations:

Focal/diffuse wall thickening (hard
to distinguish from chronic
cholecystitis)

Discrete intraluminal mass



Mass replacing the gallbladder
(most common)



Shape: well-differentiated, papillary
Density: hypointense
Notice here the distinct mass
within the gallbladder wall.
Shape: irregular
density: heterogeneous
enhancement 2° to tumor necrosis)
All may demonstrate dilated bile
ducts 2° to obstruction and/or tumor
extension to adjacent structures
Here the neoplasm appears to be
replacing the normal gallbladder
(the gallbladder wall also appears
thickened).
Photos Lee et al, 1998
Part IV
Pancreas
Pancreas Anatomy





Pancreas runs obliquely
Retroperitoneal
Tail: next to spleen
Body:
Portal vein
 Ant to left kidney
 Ant to sup mesenteric a.
Head:
 Med to 2nd part of duodenum
Spleen
Pancreas
Sup mesenteric vein
Sup mesenteric
artery
Duodenum
Pancreas on CT

Need several slices to identify all parts of
pancreas (due to its oblique orientation)

Important to know and make use of
surrounding anatomy to locate the
pancreas
Locating the Tail of the Pancreas

The tail lies next to
the spleen and
ventral to the splenic
vein (SV). It is the
first part to come into
view when advancing
through slices
superior-to-inferior.
Locating the Body of the Pancreas
Pancreatic duct

The body next comes
into view. One can
recognize it by its
tongue-like shape,
and by the
hypodense
pancreatic duct that
runs horizontally
through it.
Locating the Head of the Pancreas
on CT

The head lies next
to the second part
of the duodenum
and actually wraps
around and lies
dorsal to the SMV
and SMA:
CBD=common bile duct;
SMV=superior mesenteric vein;
SMA=superior mesenteric artery;
D=duodenum; P=pancreas head
Use the following video of
successive abdominal CT crosssectional slices to familiarize
yourself with locating the various
parts of the pancreas
Left click on the image to play
Coronal views of the body illustrating
the various parts of the pancreas
duodenum
spleen
tail
Can you also see the lesions in the liver? These are hypovascular
metastases (this is the same patient from the prior movie).
head
Systematic Approach to Viewing
the Pancreas
Things to observe:
 Size and shape:
 Tongue-shaped,12-15cm long
 Diameters:
 Head: max 3cm
 Body: max 2.5cm
 Tail: max 2.0cm
 Duct: 3-4mm, tapering at tail


Density: similar to liver parenchyma
Margins: normally appear fluffy
Abnormalities – Acute Pancreatitis
Typical Presentation:
 Size/shape: swollen,
diffuse enlargement
 Density: may not
enhance w/contrast
(signals necrosis)
 Margins: ill-defined
 Surroundings:
inflammation
Photo Lee et al, 1998
inflammation
The pancreas is diffusely enlarged
and there is inflammation in the
surrounding area, notably around the
kidneys
Abnormalities - Acute Pancreatitis Pseudocysts
Presentation:
 Size: enlarged to varying
degrees (cyst can be up to
several cm in diameter)
 Shape: cyst is usually rounded
and well-circumscribed
 Density: cyst is hypodense,
thick walled area within
pancreas
 Surroundings: peripancreatic
fluid collections/inflammation
may be present
Note the large pseudocyst in the head
of the pancreas.
Abnormalities - Chronic
Pancreatitis

Size and shape:

Pancreas: may enlarge
generally or focally, or may
appear atrophied
 Duct: may be enlarged and
irregular


Density: areas of fibrosis and
calcification appear
hyperintense w/contrast
Surroundings: surrounding
fluid collections may not be
present
Chronic pancreatitis, demonstrating
numerous areas of calcification
Abnormalities – Pancreatic
Carcinoma
Most neoplasms are adenocarcinomas
occurring in the head (2/3)

Size and shape:
 tumor size can be variable; focal
mass deforms the outline of the
gland
 Pancreatic duct may be dilated 2°
to obstruction by tumor

Density:
 tumor of lower density than
pancreatic tissue on enhanced CT

Surroundings:
 tumor spread to lymph nodes,
liver, surrounding vessels
common
A tumor in the body of the pancreas
has greatly deformed the shape of the
pancreas.
Quiz Time
Can you find the pancreas? What
part is located here?
Answer

The pancreatic body
and tail are seen on
this slice. Notice the
tail lying next to the
spleen. Also note the
pancreatic duct
running through the
body.
Pancreatic duct
tail
spleen
Can you tell what the abnormality
is?
Answer

This is acute pancreatitis.
Note the diffusely
enlarged pancreas and
considerable
inflammation surrounding
it (especially apparent
around the kidneys)
Inflammation
Can you identify the abnormality?
Photo, Lee et al, 1998
Answer

There is a pancreatic
pseudocyst in the head of
the pancreas. There is
not a lot of peripancreatic
inflammation present,
largely because this
represents a pseudocyst
that has been resolving
over time.
Pseudocyst
References
Armstrong, P, et al. Diagnostic Imaging, 5th Ed. Blackwell Publishing,
Malden. 2004.
Brant WE and Helms CA. Fundamentals of Diagnostic Radiology, 2nd
Ed. Williams and Wilkins, Baltimore. 1999.
Lee, JKT, et al. Computed Body Tomography with MRI Correlation, 3rd
Ed. Lippincott-Raven, Philadelphia. 1998.
Netter FH, Atlas of Human Anatomy, 3rd Ed. Icon Learning Systems,
Teterboro. 2003.
Novelline RA. Squire’s Fundamentals of Radiology, 6th Ed. Harvard
University Press, Cambridge. 2004.
www.learningradiology.com
www.e-radiography.net