LIVER TRANSPLANTATION
Category: Diagnostic Radiology
Abstract : LIVER TRANSPLANTS - Indications for transplant Liver transplantation has now
become a successful treatment for many chronic liver conditions and is also used
in the treatment of fulminant hepatic failure. The range of indications has
steadily increased as surgical techniques have developed and immunosuppression
has improved. The majority of hepatic transplants (80%) are still performed
LIVER TRANSPLANTS - Indications for transplant
Liver transplantation has now
become a successful treatment for many chronic liver conditions and is also used
in the treatment of fulminant hepatic failure. The range of indications has
steadily increased as surgical techniques have developed and immunosuppression
has improved.
The majority of hepatic transplants (80%) are still performed in
patients with cirrhosis and primary cholestatic disease. The 5-year survival
rate is between 65 and 90%.32,33 This is highly dependent upon both the primary
disease and upon the clinical state of the patient. Currently, seven centres in
the UK perform liver transplants, totalling around 700 patients per year. This
figure has remained relatively stable for some time and is dependent upon the
availability of donor organs.
Worldwide, the most common cause for liver
transplantation is hepatitis C. The indications for transplant are now many and
varied and the number of absolute contraindications continues to dwindle,
including AIDS and extrahepatic malignancy. Transplantation in patients with
malignant liver disease has a poorer prognosis with a lower 5-year survival.
However, the presence of small HCCs in patients with chronic liver disease is
not a contraindication, and tumour recurrence is uncommon in these patients.
Patients with larger HCCs (> 3 cm) and those with cholangiocarcinoma have a
higher rate of recurrence post-transplant, and are generally not considered for
transplantation.
Preoperative assessment
The ultrasound scan is one of
many investigations leading up to transplantation. The diagnosis of liver
pathology often uses ultrasound scanning as a first line, augmented by histology
and additional cross-sectional imaging. The role of ultrasound includes
contributing to, or confirming, the initial diagnosis, assessing the degree of
severity and associated complications of the disease and providing guidance for
biopsy. An important objective is also to exclude patients for whom liver
transplant is not feasible, or of little benefit, for example those with
extrahepatic malignant disease. The preoperative scan includes all the features
of any abdominal ultrasound survey, with the emphasis on assessing the
complications of the disease, depending upon the initial diagnosis.
In
particular, the sonographer should look for:
● Portal vein thrombosis: this
may be a contraindication to transplant if it is extensive, or unable to be
effectively bypassed by the surgeon.
● Any of the features of portal
hypertension associated with chronic liver disease.
● Focal liver lesions
which may represent malignancy. These may require the administration of
ultrasound contrast agents, or further imaging to characterize, such as MRI. An
HCC greater than 3 cm in diameter has an 80% chance of recurrence
post-transplant. If under 2 cm and solitary, this is likely to be cured. Check
the size, number and local spread of disease.
● It is useful to document the
spleen size as a baseline for postoperative comparisons.
● Extrahepatic
malignancy, in cases with an initial diagnosis of carcinoma.
● Degree and
scope of vascular thrombosis in cases of BCS.
● Any incidental pathology
which may alter the management plan.
Doppler ultrasound is, of course,
essential in assessing the patency and direction of blood flow of the portal
venous system, the hepatic veins, IVC and main hepatic artery. It may
occasionally be possible to demonstrate arterial anomalies. While large numbers
of patients are considered for transplant and undergo ultrasound assessment, the
majority of these will never actually be transplanted. This factor has numerous
implications for resources when setting up a transplant ultrasound
service.
Operative procedure
Most transplants are orthotopic, that is
the diseased liver is removed and replaced by the donor organ, as opposed to
heterotopic, in which the donor organ is grafted in addition to the native organ
(like most kidney transplants). If the patient suffers from extensive varices,
which may bleed, the removal of the diseased organ prior to transplant is
particularly hazardous.
Donor livers which are too large for the
recipient, for example in small children, may require cutting down to reduce the
size. There is an increasing trend towards a split liver technique, in which
the donor liver is divided to provide for two recipients. The lack of donors has
also led to the development of living-related donor transplantation for
paediatrics.
The transplant requires five surgical anastomoses:
●
suprahepatic vena cava
● infrahepatic vena cava
● hepatic artery (either
end-to-end, or end-toside to aorta)
● PV
● CBD (the gallbladder is
removed).
IOUS is useful for assessing the size and spread of
intrahepatic neoplastic growths and to assess vascular invasion in the
recipient. Mapping of the hepatic vascular anatomy in living-related donors is
also feasible using IOUS. IOUS with Doppler is also useful for assessing the
vascular anastomoses and establishing if portal venous and hepatic arterial flow
are adequate.
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