Diagnostic ultrasound ( PDFDrive )

CHAPTER 51 The Pediatric Liver and Spleen 1731
A
B
C
FIG. 51.1 External Segmental Anatomy of the Liver. Segments are numbered in a counterclockwise direction. Their borders are marked with
string. (A) Upper and anterior surface. Note the whitish falciform ligament that separates segments 3 and 4. (B) Lower surface: the forceps are
in the main portal vein. The gallbladder has been removed from its bed, which separates segments 4 and 5. The vertical string between segments
4 and 5 and between 1 and 7 follows the gallbladder/middle hepatic vein axis and marks the main hepatic issure, the division between right and
left lobes. Segment 1, the caudate lobe, is to the right of the forceps. Segments 3 and 4 are separated by the falciform ligament; 1 and 2 by the
ligamentum venosum. (C) Schema of the hepatic segments with their portal venous branches (upper anterior, viewed as in [A]). (D) Diagram of
the portal and hepatic veins and their relationship to the segments (lower liver surface, viewed as in [B]). (With permission from Ikeda S, Sera Y,
Yamamoto H, Ogawa M. Effect of phenobarbital on serial ultrasonic examination in the evaluation of neonatal jaundice. Clin Imaging.
1994;18[2]:146-148. 4 )
D
Each lobe of the liver contains four segments. he segments are
numbered counterclockwise: 1 through 4 make up the let lobe,
and 5 through 8, the right lobe. Segment 1 is the caudate lobe
or Spiegel lobe. he right and let lobes are separated by the
main hepatic issure, a line connecting the neck of the gallbladder
and the let side of the inferior vena cava (IVC) (Fig. 51.1).
he segmental branches of the portal vein (each one of which
leads into a segment) can be outlined in the form of two Hs
turned sideways, one for the let lobe (segments 1-4) and one
for the right lobe (segments 5-8) (Fig. 51.2).
Portal Vein Anatomy
Left Lobe of Liver
he H of the let lobe is visualized with an oblique, upwardly
tilted subxiphoid view. he H is formed by the let portal vein,
the branch entering segment 2, the umbilical portion of the let
portal vein, and the branches to segments 3 and 4. To this
recumbent H are attached two ligaments, the ligamentum
venosum, also called the “lesser omentum” or the “hepatogastric
ligament,” and the falciform ligament. he ligamentum venosum
separates segment 1 from segment 2. he falciform ligament is
visible between the umbilical portion of the let portal vein 2
and the outer surface of the liver. It separates segment 3 from
segment 4.
Segment 1, the caudate lobe, is bordered posteriorly by the
IVC, laterally by the ligamentum venosum, and anteriorly by
the let portal vein. Unlike the other segments of the liver, segment
1 may receive branches of the let and right portal veins. he
portal veins to segment 1 are usually small and are rarely seen
sonographically. he caudate lobe has one or more hepatic veins
that drain directly into the IVC, separately from the three main
hepatic veins. 3 his special vascularization is a distinctive
characteristic of segment 1.
he portal vein leading to segment 2 is a linear continuation
of the let portal vein, completing the lower horizontal limb of
the H. Segmental branches to segments 3 and 4 form the other
horizontal limb. Segments 2 and 3 are thus located to the let