Download cross-sectional-anatomy-liver-part-2

HHHoldorf
 Traditionally,
the liver has been described as
having four lobes, namely, right, left,
caudate, and quadrate. With the advent of
surgical resection of focal hepatic lesions,
the gross lobar anatomy has been modified
to reflect the surgical approach which is
based on segmental divisions.
 Couinaud
Segment
 1 Caudate lobe
 2 Left lobe, lateral segment
 3 Left lobe, lateral segment
 4 Left lobe, medial segment
 5 Right lobe, anterior segment
 6 Right lobe, anterior segment
 7 Right lobe, posterior segment
 8 Right lobe, posterior segment
 The
Couinaud classification of liver anatomy
divides the liver into eight functionally
independent segments.
Each segment has its own vascular inflow,
outflow and biliary drainage.
In the centre of each segment there is a
branch of the portal vein, hepatic artery and
bile duct.
In the periphery of each segment there is
vascular outflow through the hepatic veins.
 Right
hepatic vein divides the right lobe
into anterior and posterior segments.
Middle hepatic vein divides the liver into
right and left lobes (or right and left hemi
liver). This plane runs from the inferior
vena cava to the gallbladder fossa.
Left hepatic vein divides the left lobe into
a medial and lateral part.
 Portal vein divides the liver into upper and
lower
segments.
The left and right portal veins branch
superiorly and inferiorly to project into the
center of each segment.
 Because
of this division into self-contained
units, each segment can be resected without
damaging those remaining. For the liver to
remain viable, resections must proceed along
the vessels that define the peripheries of
these segments. This means, that resectionlines
parallel
the
hepatic
veins,
The centrally located portal veins, bile
ducts, and hepatic arteries are preserved.
 Segmental
liver anatomy is based on fissures
which contain the major hepatic veins and or
ligaments which are easily identified with
ultrasound and CT imaging. The hepatic veins
course between the hepatic lobes and
segments, whereas the portal vessels are
essentially within the liver lobes and
segments. With segmental liver anatomy,
here are three lobes and four segments to
consider…
 The
MAIN LOBAR FISSURE divides the right
and left lobes. This fissure is identified by
the middle hepatic vein superiorly, and by
an echogenic line between the right portal
vein and the gallbladder inferiorly. The
echogenic line represents fibro-fatty tissue
in the main lobar fissure. It may be a useful
landmark in identifying a contracted or
stone-filled gallbladder (or a porcelain
gallbladder).
 The
right inter-segmental fissure divides
the right lobe into anterior and posterior
segments. The only landmark which
identifies this fissure on ultrasound is the
right hepatic vein.
 The
left inter-segmental fissure divides the
left lobe into medial and lateral segments
(part of the medial segment is the quadrate
lobe). This fissure may be identified by three
landmarks on ultrasound:
 left hepatic vein (superior portion)
 anterior turn of the left portal vein (middle
portion)
 Falciform ligament and Ligamentum teres
(inferior portion)

The left portal vein has a characteristic “hook”
configuration on Sagittal scans. The Ligamentum
teres or round ligament of the liver is the
obliterated umbilical vein from embryological
development. It courses along the undersurface
of the Falciform ligament between the umbilicus
and the inferior portion of the left
intersegmental fissure. The Ligamentum teres
separates from the Falciform ligament and
extends to the left portal vein (with which it
communicated in fetal life). On Sagittal section,
it appears as a linear echo dense structure. ON
transverse section, the Ligamentum teres is seen
as a circular structure. Strong attenuation by the
Ligamentum teres may cause acoustic shadowing
and it may be mistaken for a calcified lesion
 The
CAUDATE lobe has four distinct
sonographic landmarks:
 IVC posterior
 Proximal portion of the left portal veinantero-inferior
 fissure of the Ligamentum venosum-left
anteriolateral margin
 main portal vein-inferior
 The caudate lobe is supplied by branches of
the left and right portal venous and hepatic
arterial systems, and is drained by small
caudate veins which enter directly into the
IVC. The caudate vessels are infrequently
seen in normal patients.

Caudate Lobe. The caudate lobe (c) is
between the inferior vena cava (I) and the
fissure of the ligamentum venosum (long
arrow). The inferior vena terminates in the
right atrium (A). The curved arrow indicates
the right hepatic vein. Also seen are the
portal vein (p) and the hepatic artery (short
arrow).
 The
caudate lobe is situated upon the
postero-superior surface of the liver on the
right lobe of the liver, opposite the tenth
and eleventh thoracic vertebrae. It is
bounded on the left side by the
ligamentum venosum.
 It
is bounded, below, by the portal vein; on
the right, by the fossa for the inferior vena
cava, and on the left by the fossa for the
ductus venosus.
 Structure:
RHV
 Location: Right inter-segmental fissure
 Usefulness: Divides cephalic aspect of
anterior and posterior segments of right
lobe.
 Structure:
MHV
 Location: Main Lobar Fissure
 Usefulness: Separates right and left lobes
 Structure:
LHV
 Location: Left inter-segmental fissure
 Usefulness: Divides cephalic aspects of
medial and lateral segments of left lobe
 Structure:
RPV (anterior branch)
 Location: Intra-segmental in anterior
segment of right lobe
 Usefulness: Courses centrally in anterior
segment of right lobe.
 Structure:
RPV (posterior branch)
 Location: Intra-segmental in posterior
segment of right lobe
 Usefulness: Courses centrally in posterior
segment of right lobe.
 Structure:
LPV (horizontal segment)
 Location: Anterior to caudate lobe
 Usefulness: Separates caudate lobe
Posteriorly from medical segment of left lobe
anteriorly.
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Structure: LPV (ascending segment)
Location: Left inter-segmental fissure
Usefulness: Divides medal and lateral segments of left lobe
Structure: GB fossa
Location: Main Lobar fissure
Usefulness: Separates right and left lobes
Structure: Fissure for the Ligamentum teres
Location: Left inter-segmental fissure
Usefulness: Divides caudal aspect of left lobe into medial
and lateral segments.
Structure: Fissure for the Ligamentum venosum
Location: left anterior margin of caudate lobe
Usefulness: Separates caudate lobe Posteriorly from left
lobe anteriorly.
 Ligamentum


Round appearance on transverse view.
Represents the remnant of fetal umbilical vein.
 Ligamentum

teres:
Venosum:
Remnant of the ductus venosus of the fetal
circulation.
 Create
a storyboard explaining the segmental
anatomy of the liver.
 Utilize diagrams, ultrasounds, and CT scans
 Include in your story board the following:
 Left portal vein-the bifurcation of the left
portal vein into medial and lateral branches
demonstrated on a transverse scan.
 The
hepatic veins (transverse sub costal
scan of the liver – showing the three main
hepatic veins. showing the following
 Right lobe
 left lobe
 anterior segment
 posterior segment
 lateral segment
 medial segment
 right hepatic vein
 middle hepatic vein
 left hepatic vein
 inferior vena cava
 Normal
liver segmental anatomy showing the
right portal vein- transverse sub costal scan
of the liver showing the right portal vein
dividing to anterior and posterior branches.
 The echo texture of the normal liver
 Main lobar fissure
 left, right, caudate lobe
 Fissure of the Ligamentum teres
 Fissure of the Ligamentum venosum
 GB fossa