Diagnostic ultrasound ( PDFDrive )

CHAPTER 4 The Liver 77
TABLE 4.1 Structures Useful for Identifying Hepatic Segments
Structure Location Usefulness
Right hepatic vein Right intersegmental issure Divides cephalic aspect of anterior and
posterior segments of right lobe
Middle hepatic vein Main lobar issure Separates right and left lobes
Left hepatic vein Left intersegmental issure Divides cephalic aspect of medial and lateral
segments of left lobe
Right portal vein (RPV) (anterior
branch)
Intrasegmental in anterior segment of
right lobe
Courses centrally in anterior segment of right
lobe
RPV (posterior branch)
Intrasegmental in posterior segment of Courses centrally in posterior segment of right
right lobe
Anterior to caudate lobe
lobe
Separates caudate lobe posteriorly from
medial segment of left lobe anteriorly
Left portal vein (LPV) (horizontal
segment)
LPV (ascending segment) Left intersegmental issure Divides medial from lateral segment of left
lobe
Gallbladder fossa Main lobar issure Separates right and left lobes
Fissure for ligamentum teres Left intersegmental issure Divides caudal aspect of left lobe into medial
and lateral segments
Fissure for ligamentum venosum Left anterior margin of caudate lobe Separates caudate lobe posteriorly from left
lobe anteriorly
Modiied from Marks W, Filly R, Callen P. Ultrasonic anatomy of the liver: a review with new applications. J Clin Ultrasound. 1979;7(2):137-146. 2
TABLE 4.2 Couinaud Segments and
Traditional Hepatic Anatomy
Couinaud
Segment I
Segment II
Segment III
Segment IV
Segment V
Segment VI
Segment VII
Segment VIII
Traditional
Caudate lobe
Lateral segment left lobe (superior)
Lateral segment left lobe (inferior)
Medial segment left lobe
Anterior segment right lobe (inferior)
Posterior segment right lobe (inferior)
Posterior segment right lobe (superior)
Anterior segment right lobe (superior)
the medial segment of the let lobe. he right lobe consists of
segments V and VI, located caudal to the transverse plane, and
segments VII and VIII, which are cephalad 4,5 (Fig. 4.5). he
caudate lobe (segment I) may receive branches of both the right
and the let portal vein. In contrast to the other segments, segment
I has one or several hepatic veins that drain directly into the
IVC.
he portal venous supply for the let lobe can be visualized
using an oblique, cranially angled subxiphoid view. A “recumbent
H” is formed by the main let portal vein, the ascending branch
of the let portal vein, and the branches to segments II, III, and
IV 6 (Fig. 4.6). Segments II and III are separated from segment
IV by the let hepatic vein, as well as by the ascending branch
of the let portal vein and the falciform ligament. Segment IV
is separated from segments V and VIII by the middle hepatic
vein and the main hepatic issure.
he portal venous supply to the right lobe of the liver can
also be seen as a recumbent H. he main right portal vein gives
rise to branches that supply segments V and VI (inferiorly) and
VII and VIII (superiorly). hey are seen best in a sagittal or
oblique sagittal plane. 6
he oblique subxiphoid view shows the right portal vein in
cross section and enables identiication of the more superiorly
located segment VIII (closer to conluence of hepatic veins) from
segment V. Segments V and VIII are separated from segments
VI and VII by the right hepatic vein. 6
Ligaments
he liver is covered by a thin connective tissue layer called Glisson
capsule. he capsule surrounds the entire liver and is thickest
around the IVC and the porta hepatis. At the porta hepatis, the
main portal vein, the proper hepatic artery, and the common
bile duct are contained within investing peritoneal folds known
as the hepatoduodenal ligament (Fig. 4.7). he falciform ligament
conducts the umbilical vein to the liver during fetal
development (Fig. 4.8). Ater birth, the umbilical vein atrophies,
forming the ligamentum teres (Fig. 4.9). As the falciform ligament
reaches the liver, its leaves separate. he right layer forms the
upper layer of the coronary ligament; the let layer forms the
upper layer of the let triangular ligament. he most lateral portion
of the coronary ligament is known as the right triangular ligament
(Fig. 4.10). he peritoneal layers that form the coronary ligament
are widely separated, leaving an area of the liver not covered by
peritoneum. his posterosuperior region is known as the bare
area of the liver. he ligamentum venosum carries the obliterated
ductus venosus, which until birth shunts blood from the umbilical
vein to the IVC.