Diagnostic ultrasound ( PDFDrive )

78 PART II Abdominal and Pelvic Sonography
RHV
MHV
IVC
LHV
2
7
2
5/8
4
3
8
1
4
3
6
5
6/7
A
PV
FIG. 4.5 Couinaud Functional Segmental Anatomy. (A) The liver is divided into nine segments. Blue longitudinal boundaries (right, middle,
and left scissurae) are three hepatic veins. Transverse plane is deined by right main and left main portal pedicles. Segment I, caudate lobe, is situated
posteriorly. (B) Corresponding sonogram shows the main portal vein with its right and left branches. The plane through the right and left branches
is the transverse separation of the liver segments. Cephalad to this level lie segments II, IVa, VII, and VIII. Caudally located are segments III, IVb,
V, and VI. GB, Gallbladder; LHV, left hepatic vein; LPV, left portal vein; MHV, middle hepatic vein; RHV, right hepatic vein; RPV, right portal vein.
(With permission from Sugarbaker PH: Toward a standard of nomenclature for surgical anatomy of the liver. Neth J Surg. 1988;PO:100. 5 )
B
5/8 5/8
4
3
R
6/7 6/7
L
R
L
2
A
B
FIG. 4.6 Portal Venous Anatomy in Two Patients. (A) Best seen with a subcostal oblique view, the main portal vein is formed by the union
of the right and left portal venous branches at the porta hepatis. (B) Segmental branches of the right and left portal veins are marked. Well seen
is the recumbent-H shape of the left portal venous bifurcation, made from the ascending and horizontal left portal vein and the segmental branches
to 2, 3, and 4.
Hepatic Circulation
Portal Veins
he liver receives a dual blood supply from both the portal vein
and the hepatic artery. Although the portal vein carries incompletely
oxygenated (80%) venous blood from the intestines and
spleen, it supplies up to half the oxygen requirements of the
hepatocytes because of its greater low. his dual blood supply
explains the low incidence of hepatic infarction.
he portal triad contains a branch of the portal vein, hepatic
artery, and bile duct. hese are contained within a connective
tissue sheath that gives the portal vein an echogenic wall on
sonography and that distinguishes it from the hepatic veins,
which have an almost imperceptible wall. he main portal vein
divides into right and let branches. he right portal vein has
an anterior branch that lies centrally within the anterior segment
of the right lobe and a posterior branch that lies centrally within
the posterior segment of the right lobe. he let portal vein
initially courses anterior to the caudate lobe. he ascending branch
of the let portal vein then travels anteriorly in the let intersegmental
issure to divide the medial and lateral segments of the
let lobe.
Arterial Circulation
he branches of the hepatic artery accompany the portal
veins. he terminal branches of the portal vein and their accompanying
hepatic arterioles and bile ducts are known as the
acinus.