Diagnostic ultrasound ( PDFDrive )

638 PART II Abdominal and Pelvic Sonography
53.0 cm/s
F
120.1 cm/s
E
156.0 cm/s
A B C
FIG. 18.15 Portal Vein Stenosis: Anastomotic Stricture. (A) Gray-scale sonogram of main portal vein shows narrowing at the anastomosis
(arrowhead). (B) Color Doppler shows aliasing at the region of stenosis caused by high-velocity turbulent low. (C) Spectral Doppler shows velocities
of 32.8 cm/sec proximal to the stenosis. (D) Velocities at the stenosis are elevated at 156 cm/sec. (E) Poststenotic high-velocity turbulent low is
identiied, measuring 120.1 cm/sec. (F) Beyond the turbulent low, velocities of 53 cm/sec are obtained. This represents a threefold increased
velocity gradient across the anastomosis, indicating that the stenosis is hemodynamically signiicant.
D
32.8 cm/s
Extrahepatic Fluid Collections
Perihepatic luid collections and ascites are frequently observed
ater transplantation. In the early postoperative period a small
amount of free luid or a right pleural efusion may be observed,
but these usually resolve in a few weeks. Fluid collections and
hematomas are common in the areas of vascular anastomosis
(hepatic hilum and adjacent to IVC) and biliary anastomosis,
in the lesser sac, and in the perihepatic and subhepatic spaces. 7
Because the peritoneal relections surrounding the liver are ligated
at transplantation, luid collections can occur around the bare
area of the liver, a location for luid that is not encountered in
the preoperative liver 5 (Fig. 18.22).
Ultrasound is highly sensitive in detecting these luid collections,
although it lacks speciicity with regard to etiology because
bile, blood, pus, and lymphatic luid can all have a similar
sonographic appearance. he presence of internal echoes in a
luid collection suggests blood or infection. Particulate ascites
may also be observed in peritoneal carcinomatosis, although
this would seem less likely in the transplant recipient
population. 5
Adrenal Hemorrhage
Right-sided adrenal hemorrhage may be observed in the immediate
postoperative period and results from (1) venous engorgement
caused by ligation of the right adrenal vein during the removal
of a portion of the IVC or (2) a coagulopathy caused by the
patient’s preexisting liver disease. 26 On ultrasound, adrenal
hemorrhage may be seen as a hypoechoic nodular structure or
as a luid collection in the right suprarenal region (Fig. 18.23).
Intrahepatic Fluid Collections
Sterile postoperative luid collections are oten located along the
falciform ligament and ligamentum venosum, usually appearing
as luid-illed anechoic collections surrounding the echogenic
ligaments (Fig. 18.24). Bilomas may manifest as a hypoechoic
or complex cyst. Intraparenchymal hematomas may result from
the transplant surgery or percutaneous biopsy or may be a sequela
of donor trauma (e.g., motor vehicle crash).
Abscess Versus Infarct
In the early stages it may be diicult to diferentiate a liver abscess
from an infarct. Initially, both abscesses and infarcts may appear
as a subtle hypoechoic region, associated with a localized coarsening
of the parenchymal echotexture. Infarcts may subsequently
organize into avascular round or wedge-shaped lesions, which
can eventually develop central hypoechoic areas relecting liquefaction
and necrosis. A focal liver infarct should be diagnosed
with accompanying Doppler evidence of hepatic arterial
compromise.
As with infarcts, the ultrasound appearance of a liver abscess
also varies with its maturation. he classic appearance of a mature
transplant liver abscess is a complex, cystic structure with thick,