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Liver - Anatomy
Largest of all abdominal organs, commands the right
upper abdominal quadrant
Great transverse measurement -20 to 26 cm
Vertically measurement- 15 to 21 cm
Greatest anteroposterior diameter (determined at
the level of the upper right kidney) - 7 to 12 cm.
The hepatic parenchyma is surrounded by a dense
layer of connective tissue forming the liver capsule.
convex diaphragmatic surface
concave visceral surfaces.
Bare area , Fossa of the gallbladder, fossa of the
inferior vena cava (IVC), and the suprarenal impression
are not covered by peritoneum.
• Two sagitally oriented fissures
linked centrally by transverse
porta hepatis , form the letter
H on visceral surface.
• Left fissure – Fissure for round
ligament anteriorly and
fissure for ligamemtum
• Right fissure – Fossa for GB
anteriorly and groove for IVC
Functional segmental anatomy
Centrally located in each of the hepatic segments
segmental branch of the portal vein
segmental bile duct.
The distal hepatic veins lie
between the individual
Divides the liver into 8 functionally independent
Each segment has its own vascular inflow ,
outflow and biliary drainage.
Centre – Hepatic artery , portal vein and bile duct.
Periphery – Vascular outflow through hepatic
Segment I -caudate lobe.
Receives branches from both the main portal vein
and its right and left branches - portal trinity.
Does not drain into the hepatic veins but directly
into the IVC.
All remaining liver segments (II to VIII) are defined
by their positions relative to branches of the portal
and hepatic veins.
Left portal vein
Gives off a caudate branch.
Divides into its terminal branches - left lateral
and left medial portal venous branches.
The left lateral portal venous branch supplies
superior segment II, located lateral to the left
hepatic vein and above the portal venous plane.
The left medial portal venous branch supplies
inferior segment III located laterally to the left
hepatic vein and beneath the portal venous plane
as well as segment IV.
• Segment IV is delineated
• Medially - middle hepatic vein and
• Laterally - left hepatic vein
• Subdivided into a superior segment IVa and an
inferior segment IVb in regard to the portal venous
Right portal vein
The right anterior portal venous branch
anterior-inferior segment V
anterior-superior segment VIII
The right posterior portal venous branch
posterior-inferior segment VI
posterior-superior segment VII
LIVER ANATOMY VARIANTS
• Horizontal elongation of the lateral segment
(bismuth-couinaud segment II) of the left
hepatic lobe, which can extend into the left
upper abdominal quadrant and eventually
abut or even wrap around the splenic contour.
• Riedel lobe - vertical
elongation of the right
• Differentiated from
caused by a liver tumor (
hepatic adenoma or
Precontrast T1-weighted hepatic MRI in a
77-year-old woman with Riedel’s lobe
resulting from a prominent inferiorly
positioned narrow right lobe of the liver
that significantly extends the expected
confines of the liver.
On computed tomography , normal intra hepatic bile ducts
appear as linear water-density structures accompanying the portal
Normal IHDs measure less than 3 mm.
They appear to be randomly scattered throughout the liver
but are confluent toward the hilum.
The IHDs from each lobe unite to form the right and left main
hepatic ducts, which are located anterior to the portal veins .
Common hepatic duct
The right and left main hepatic ducts unite in
the hilum to form the common hepatic duct
The CHD usually courses along a 45-degree
oblique plane with reference to the midline
sagittal plane, which lies to the right and
lateral to the proper hepatic artery.
On CT the CHD usually measures 3 to 6 mm
in short-axis diameter
Common bile duct
The common bile duct (CBD) forms when the
cystic duct joins the CHD.
This union occurs at varying levels, from high
in the porta hepatis to near the ampulla of
Because the union is usually not
demonstrated on CT, the term common duct
is used when the CHD and CBD cannot be
THE UNION IS USUALLY NOT DEMONSTRATED
ON CT, THE TERM COMMON DUCT IS USED
WHEN THE CHD AND CBD CANNOT BE
Ampulla of Vater
The CBD enters the pancreas and typically lies along the
posterior and lateral aspect of the pancreatic head.
The distal CBD and main pancreatic duct come into contact
on the medial side of the descending part of the
The two ducts pass separately
through the wall of the
duodenum and unite to form
a short dilated tube—the
ampulla of Vater
• The sphincter of Oddi is the circular muscle
complex around the CBD, pancreatic duct, and
ampulla of Vater; it consists of the
• sphincter choledochus
• sphincter pancreaticus and
• sphincter ampullae
On endoscopic retrograde cholangio pancreatography,
the ampullary segment is usually not visualized
because of the contraction of the sphincter of Odd.
• The gallbladder is a blind
pouch lying along the
undersurface of the liver.
• The normal gallbladder
wall thickness ranges from
1 to 3.5 mm. On US, 3 mm
might be a reasonable
upper limit of normal.
Normal GB wall appears s a pencil thin
echogenic line at sonography
Minimum 6 hrs fasting
Subcoastal or intercostal
Supine – LLD
GB wall - <3mm
Transverse diameter - <4cm
• On transverse CT images, the gallbladder is a
rounded structure with a maximum diameter
of less than 4 to 5 cm in the distended state.
• Visualization of the gallbladder wall depends
on the degree of gallbladder distention and
the presence of abnormality.
• Enhancement of the gallbladder wall on CT
and MRI is normal after the intravenous
administration of contrast medium.
• The density of the gallbladder lumen is
generally that of water (0-20 Hounsfield units
• After intravenous contrast administration, an
increase in density is observed on CT.
Normal GB wall apperas as a thin
rim of soft tissue density that
enhances on contrast
The most common anomaly of the entire
Septation in the distal fundus of the
gallbladder, which results in the configuration
called a phrygian cap.
In the retroserosal or concealed type, the
mucosal fold projecting into the lumen may
not be visible externally.
In the serosal or visible type, the
peritoneum follows the bend in the fundus
and then reflects on itself as the fundus
overlies the body.
Ectopic gall bladder
can be located in
CT ANATOMY - PANCREAS
The density of the nonenhanced pancreas is
normally the same as that of soft tissue, between
30 and 50 HU. It increases to 100 to 150 HU after
intravenous administration of iodine-based
Homogeneous enhancement of the normal gland is
a useful sign for excluding necrosis in pancreatitis.
PANCREAS LIES OBLIQUE , HENCE ALL
PARTS ARE NOT AT THE SAME
MRI ANATOMY - PANCREAS
On T1-weighted images, the normal gland, owing to the
aqueous protein content, reveals higher signal
intensity than nonfatty tissue such as liver and
On fat-suppressed T1-weighted sequences, the
relatively high signal intensity of the pancreas
On T2-weighted sequences, the normal pancreas is
slightly hyperintense to muscle, whereas on fat-
suppressed T2-weighted images, the contrast
between the normal pancreas and surrounding
suppressed fat is minimal
Being a very vascular organ, the pancreas shows
intense contrast enhancement in the arterial
phase, followed by a rapid washout (
• Failure of fusion of the dorsal and ventral ducts
• Separate drainage into duodenum - Predominant
drainage occurs through dorsal duct system (duct
• Classified into three types
– I (classic form): complete lack of fusion between
dorsal and ventral duct systems
– II: absent duct of Wirsung
– III: small communicating branch connects dorsal and
ventral duct systems
portion of pancreatic tissue in continuity with the
head that partially or completely circumscribes
encircles second portion of duodenum
associated with duodenal anomalies such as atresia,
atrophy, or stenosis .
discovered in childhood because of upper GI
Agenesis of pancreas
Complete agenesis of the dorsal pancreas: body and tail
of pancreas and whole dorsal duct system, including
minor papilla and accessory duct, are absent.
Partial agenesis of the dorsal pancreas: distal part of
pancreatic body or at least a remnant of accessory
duct and minor papilla are found.
the rounded head of the
pancreas (arrow) and the
absence of the neck and body.
the abnormal position of the bowel loops
(arrowheads) behind the stomach.
• Lies within the left upper
• Weighs 100 to 200 g
• The max craniocaudal
length is 12 cm.
• The normal spleen may have rib notching and
clefts that should not be confused with
lacerations in patients who have experienced
The spleen is a network of
white and red pulp.
The white pulp consists
of lymphocytes, plasma
cells, and macrophages.
The red pulp contains
splenic cords, splenic
branches of the central
arteries, and pulp veins.
The visceral surface of the spleen is adjacent to
the stomach, left kidney, splenic flexure of the
colon, and tail of the pancreas.
Spleen – USG anatomy
Best assessed in left lateral
position with left arm
behind the head.
Visualised best obliquely in
9th or 10th intercostal space.
Higher echogenicity than
On unenhanced CT
scans, the normal
homogeneous - it
measures 40 to 60
(HU), usually 5 to
10 HU less than
the normal liver.
ROI measurement is placed within the liver and spleen.
If spleen measures 10HU or more than the liver – fatty
infiltrate is indicated.
VZAfter intravenous (IV)
the spleen can have a
appearance on early
arterial-phase images on
both CT and MRI.
This appearance is
believed to be due to
enhancement of red and
Patterns of spleen enhancement in
T1-weighted MRI the normal spleen has a
signal intensity equal to or less than that of
T2-weighted images, the spleen has
uniformly high signal intensity.
Easily recognized because of
their sharp, smooth borders.
Typically located superiorly
Splenic clefts are not
associated with perisplenic
edema ,seen with splenic
• Accessory spleen represents normal splenic tissue in
• Arising from failure of fusion of some of the multiple buds
of splenic tissue in the dorsal mesogastrium during
• They are typically located near the splenic hilum but can be
found anywhere in the peritoneal cavity
Wandering spleen - or ectopic
spleen is a rare entity
whereby the spleen migrates
from its normal site in the left
Nonunion of the peritoneum
of the lesser and greater sacs,
creating a longer splenic
mesentery and highly mobile
Single breath hold and IV administration of a contrast
90-ml bolus of nonionic contrast agent is administered
at a rate of 2 to 3 ml/second.
Scanning is performed during the portal venous phase
at 60 seconds after the bolus is given. This approach
typically provides uniform enhancement of the spleen
and enhancement of the liver during the portal venous
In any patient being evaluated for trauma, delayed
scans taken 2.5 to 3 minutes after the bolus can often
exclude lacerations of the spleen or other abdominal
Kidney - anatomy
Paired retroperitoneal organ.
Located on posterior abdominal wall.
Lies between T12 to L3.
Adult male – 10 to 14cm
Adult female – 9-13cm
Anterior renal fascia
Posterior renal fascia
The renal fascial layers divide the general retroperitoneal
space into three compartments extending from the
diaphragm to the pelvic brim—the anterior pararenal space,
the perinephric space, and the posterior pararenal space
Contains the kidney, adrenal gland, renal
pelvis, proximal ureter, renal blood vessels,
renal capsular vessels, and perinephric fat.
It is bounded by the anterior and posterior
renal fascial layers and is demarcated by their
sites of fusion.
Above -- two fascial layers fuse and adhere firmly to
the diaphragmatic fascia;
Laterally -- the layers fuse behind the ascending or
descending colon to form the lateroconal fascia
Medially -- the anterior renal fascia blends into the
connective tissue near the midline . posterior
renal fascia fuses with the psoas or quadratus
Inferiorly -- fascial cone forming a caudal extension
of the main perinephric space containing the
proximal ureter and gonadal vessels
Anterior renal fascia
Posterior renal fascia
Kidney – USG anatomy
Cortex is less echogenic than
liver and more echogenic than
Renal sinus consisting of
calyces , renal pelvis and fat
appears echogenic than cortex.
• CT protocol for evaluation of the kidneys
consists of both non enhanced and contrast-
enhanced CT scans obtained in suspended
respiration to overcome the motion artifact.
• Non enhanced CT scans the normal renal
parenchyma has an attenuation value of 30 to
50 hounsfield units (HU), depending on
patient hydration, and the cortex and medulla
show no visible density differences.
• Nonenhanced scans
permit contrast enhancement of a renal lesion to be
ensure that renal parenchymal calcifications, renal
calculi, renal and perinephric hemorrhage and fat,
and calcification in a renal mass will not be obscured
by contrast medium.
• The accuracy of attenuation values should also be
tested by measuring the attenuation value of the
gallbladder contents before and after IV
administration of contrast medium.
Corticomedullary phase occurs
between 25 and 70 seconds after
the start of contrast administration.
Renal cortex can be differentiated
from renal medulla at this stage
because (1) the vascularity of the
cortex is greater than that of the
medulla, and (2) contrast material
has not yet reached the distal aspect
of the renal tubules
Maximal opacification of the renal vein and arteries
occurs during this phase, allowing confident diagnosis of
tumor extension to the vein.
The nephrographic phase
starts about 80 seconds and lasts
up to 180 seconds after the start
Offers the best opportunity for
discrimination between the
normal renal medulla and a renal
The nephrographic phase is the most valuable for detecting
renal masses and characterizing indeterminate lesions
Approximately 180 seconds after
the start of contrast injection, the
excretory phase begins.
The contrast material is excreted
into the collecting system, so the
attenuation of the nephrogram
Delineate the relationship of a centrally located mass with the
Evaluating urothelial masses.
Normal renal MRI.
A T1-weighted (gradient opposed-phase)
T2-weighted axial image (B) demonstrate
the normal appearance of the kidneys
T1-weighted axial Gd-enhanced image
reveals normal enhancing renal
Renal ectopia - Abnormal anatomical location of
one or both the kidney.
Normal adrenal glands have a characteristic
inverted Y, V, or T shape
Right adrenal gland is typically superior to the
Left adrenal gland is usually anterior to the
superior pole of the left kidney.
The adrenals are typically described as having
a central body and two (medial and lateral) limbs.
The body and limbs are typically smoothly shaped
and measure less than 10 mm in thickness; the
limbs can measure up to 4 cm in length
Normal adrenal glands. Axial and coronal contrast-enhanced
CT demonstrates typical location and appearance of the right
and left adrenal glands
Axial contrast-enhanced T1-weighted MRI shows normal
thickness of the adrenal body and limbs (<1 cm) and normal
length (<4 cm).
Stomach These areas of the stomach
cannot always be well
demonstrated on axial CT or MRI,
so coronal or sagittal imaging
planes are very helpful to
understand the exact anatomic
location of the lesion .
Normal gastric wall is 2 to 5 mm
thick, with 10 mm being the upper
In an air-filled stomach - 3mm or
On CT or MRI, the normal gastric
wall enhances homogeneously
but shows a two- or three-
layered structure .
Inner layer- mucosal layer,
Intermediate layer - submucosal
layer low attenuation
Outer layer – muscular serosal
layer of slightly higher
Normal gastric wall of the stomach (S) with
In a suboptimally distended stomach, false-
positive gastric wall thickening can frequently
When air techniques are used
the right decubitus position -proximal stomach
the left decubitus position -distal stomach and
[reverse of the patient’s position when barium
or water is used].
Left posterior oblique position - gastric antrum
Prone position - gastric fundus
Normal small bowel wall thickness - 2 to 3
In the terminal ileum where 5 mm is
considered the upper limit of normal.
The thickness of valvulae conniventes
should not exceed 3 mm.
Normal coronal CT enterography
image after oral administration of
Gastrografin as a positive oral
Normal coronal CT enterography
image after oral administration of
water as a neutral oral contrast.
Colon and Rectum
Colon is visualized on CT by its
typical haustral morphology
Ringlike or tubular structure, depending on
the orientation and position relative to the
The wall of the normal colon measures 3
mm or less in thickness when the colon is
distended with oral contrast material.
• Caecum - Recognition of the cecum is
facilitated by visualization of the terminal
ileum, ileocecal valve, or appendix.
Appendix - The appendix appears as a
small ringlike or tubular structure. The
presence of air or contrast material in the
appendix along with normal-appearing
surrounding fat may be indicative of absence
• The ascending and descending colons are
within the anterior pararenal space and
usually are surrounded by homogeneous fatty
• The rectum is about 12 to 15 cm in length.
• The peritoneum covers the anterior surface of
the upper rectum
• Lower two thirds of the rectum are enveloped
by extraperitoneal connective and adipose