Diagnostic ultrasound ( PDFDrive )

624 PART II Abdominal and Pelvic Sonography
of transplant-related complications. hese improvements have
resulted in a 1-year patient survival rate of over 80% for each of
these organ transplants. 2,3
Because the clinical presentation of posttransplant complications
varies widely and is oten nonspeciic, imaging studies are
essential for monitoring the status of the allograt. If diagnosis
is delayed, the function of the allograt may be permanently
compromised, and in severe cases with complete loss of function,
retransplantation may be warranted. However, the chronic
shortage of suitable donor organs may delay or preclude immediate
retransplantation, with devastating clinical consequences.
herefore preservation of the allograt function and early detection
of complications, with institution of appropriate treatment, are
essential in the clinical management of these patients.
Ultrasound has revolutionized the practice of organ transplantation.
Liver, renal, and pancreatic transplants should be
assessed with gray-scale, color Doppler, and spectral Doppler
interrogation. Gray-scale sonography permits optimal assessment
of the textural and morphologic changes of the parenchyma,
and color and spectral Doppler ultrasound permit evaluation of
both parenchymal perfusion and the status of the major transplanted
artery and vein. his chapter focuses on the ultrasound
appearances of the normal organ transplant, acute and chronic
transplant-related complications, and potential errors of interpretation
that can lead to misdiagnoses.
LIVER TRANSPLANTATION
From January 1, 1988 to June 30, 2016 in the United States,
143,856 patients underwent liver transplantation. 4 One-year
survival in liver transplant patients is approximately 87%, with
1-year grat survival of 80.3%. Patients are selected for transplantation
when their life expectancy without transplantation is less
than their life expectancy ater the procedure. Hepatitis C is the
most common disease requiring transplantation, followed by
alcoholic liver disease and cryptogenic cirrhosis. Other end-stage
liver disorders treated by transplantation include chronic cholestatic
diseases, such as primary biliary cirrhosis and primary
sclerosing cholangitis; metabolic diseases, including hemochromatosis
and Wilson disease; and other hepatitides, such as
autoimmune hepatitis, chronic hepatitis B, and acute liver failure.
Patients with end-stage hepatitis B cirrhosis were initially regarded
as poor transplant candidates because of the high rate of recurrence
of infection in the implant, associated with rapid progression
to cirrhosis. he use of hyperimmunoglobulins and nucleoside
analogues has changed these expectations to a more favorable
outcome. 5
Most centers consider transplantation only in patients with
early-stage hepatocellular carcinoma (HCC) or rarely neuroendocrine
metastasis. he generally accepted guidelines for
transplantation in patients with HCC are the Milan criteria: (1)
no lesion greater than 5 cm in diameter or (2) no more than
three lesions greater than 3 cm in diameter. 5,6
Contraindications for liver transplantation include compensated
cirrhosis without complications, extrahepatic malignancy,
cholangiocarcinoma, active untreated sepsis, advanced cardiopulmonary
disease, active alcoholism or substance abuse, or an
anatomic abnormality precluding the surgical procedure. Although
portal vein thrombosis is not an absolute contraindication to
liver transplantation, its presence makes the surgery more
complex, and posttransplantation patients show higher morbidity
and mortality rates. 5
Surgical Technique
Traditionally, most adult liver transplants involve explantation
of the recipient liver and replacement with a cadaveric allograt.
he surgery requires four vascular anastomoses (suprahepatic
vena cava, infrahepatic vena cava, hepatic artery, portal vein) as
well as a biliary anastomosis (Fig. 18.1).
he hepatic artery is reconstructed with a “ish-mouth”
anastomosis between the donor common hepatic artery and
either the bifurcation of the right and let hepatic arteries or the
branch point of the common hepatic artery into the gastroduodenal
and proper hepatic arteries of the recipient. When the
native hepatic artery is small in diameter or shows minimal low,
a donor iliac artery or splenic artery interposition grat may be
anastomosed directly to the supraceliac or infrarenal aorta. 7
he end-to-end attachment of these patulous arterial ends
leads to a normally expected mild widening at the arterial
anastomosis.
he portal vein anastomosis is usually end to end between
the donor and recipient portal veins. In cases of extensive recipient
portal vein thrombosis, a venous jump grat from the donor
portal vein or the iliac vein may be used, to the portomesenteric
conluence, superior mesenteric vein (SMV), or a collateral vein,
or as a last resort, an anastomosis between both the portal vein
and the hepatic artery of the donor and the arterial vessels of
the recipient. 7,8
During hepatectomy, the inferior vena cava (IVC) of the
recipient usually is transected above and below the intrahepatic
FIG. 18.1 Normal Liver Transplant: Surgical Approach. The
transplanted liver shows four vascular anastomoses and a biliary anastomosis.
The inferior vena cava (IVC, blue) is transplanted with a
suprahepatic and infrahepatic anastomosis. An end-to-end anastomosis
is often used for the common bile duct (CBD, green) and portal vein
(PV, purple), whereas the hepatic artery (HA, red) is reconstructed with
a “ish-mouth” anastomosis.