Diagnostic ultrasound ( PDFDrive )

CHAPTER 4 The Liver 81
A
B
FIG. 4.11 Normal Liver Echogenicity. (A) The liver is more echogenic than the renal cortex. (B) The liver is less echogenic than the spleen,
as seen in many thin women, whose left lobe of the liver wraps around the spleen.
RRCCa
A
B
FIG. 4.12 Diaphragmatic Slip. (A) Sagittal sonogram shows echogenic mass (arrows) adjacent to right hemidiaphragm in this patient with
right renal cell carcinoma (RRCCa). (B) Subcostal oblique image reveals mass is diaphragmatic slip (arrows).
in only 55% of the population. he remaining 45% have some
variation of this anatomy, the main patterns of which are (1)
replaced let hepatic artery originating from the let gastric artery
(10%), (2) replaced right hepatic artery originating from the
superior mesenteric artery (11%), and (3) replaced common
hepatic artery originating from the superior mesenteric artery
(2.5%).
Congenital portal vein anomalies include atresias, strictures,
and obstructing valves, all of which are uncommon. Other
variations of anatomy include absence of the right portal vein,
with anomalies of branching from the main and let portal veins,
and absence of the horizontal segment of the let portal vein. 12
In contrast, variations in the branching of the hepatic veins
and accessory hepatic veins are relatively common. he most
common accessory vein drains the superoanterior segment of
the right lobe (segment VIII) and is seen in approximately onethird
of the population. It usually empties into the middle hepatic
vein, although occasionally it joins the right hepatic vein. 13 An
inferior right hepatic vein, which drains the inferoposterior
portion of the liver (segment VI), is observed in 10% of individuals.
his inferior right hepatic vein drains directly into the IVC
and may be as large as the right hepatic vein or larger. 14 Let and
right marginal veins, which drain into the let and right hepatic
veins, occur in about 12% and 3% of individuals, respectively.