Assessment For Liver Transplantation
As with renal transplantation, assessment of a potential
liver transplant recipient involves not only evaluation of the liver disease
for which transplantation is indicated, but also determination of comorbidity
that may affect peri or post-operative morbidity and mortality. Moreover, since
liver transplantation is now a successful treatment for liver failure, focus
has switched to ensuring longterm survival rather than just surviving the
surgical assault. The shortage of organs has necessitated increased
selectivity, favouring patients with better anticipated outcomes.
Evaluating the liver disease
Most liver screening tests are repeated to verify the
diagnosis and rule out other diseases. These are illustrated in Figure 34.
Liver biopsy may be indicated
in patients with a presumed hepatoma but otherwise good function, when biopsy
of the back-ground liver will help decide whether a liver resection is possible
rather than a transplant. In general, focal lesions are not biopsied if
they have characteristic radiological features of a hepatoma, due to the risk
of seeding the tumour outside the liver.
Upper gastrointestinal endoscopy looking for varices, ulcers and tumours.
Ultrasound examination screens for focal lesions that may represent tumours, and confirms the
presence of patent hepatic artery, and portal and hepatic veins. Hepatic vein
occlusion suggests Budd Chiari disease.
Further cross-sectional imaging may be required to characterise any focal lesion – hepatomas typically take
up contrast in the arterial phase of computed tomography (CT) and ‘wash out’
leaving a hypodense area in the portal venous phase. Magnetic resonance (MR)
imaging may help to define a lesion. The differential diagnosis of small
lesions is between regenerative nodule and hepatoma.
Nodules that have the typical appearance of tumour are
not biopsied for fear of seeding the tumour outside the liver.
Pre-transplant anti-hepatoma therapy, either radiofrequency ablation (RFA) or trans-arterial chemo-embolisation
(TACE), are considered as treatment to reduce the growth (and prevent spread)
of the tumour while the patient is on the waiting list.
Evaluating the surgical challenge
Previous upper abdominal surgery, particularly procedures in the liver hilum such as cholecystectomy or
highly selective vagotomy, result in adhesions, which become very vascular in
the presence of portal hypertension and are associated with longer surgery and
greater blood loss.
Patency of the portal vein is checked, and if thrombosed, the possibility of performing a graft from
the portal vein of the transplant to the superior mesenteric vein or left renal
vein of the recipient is assessed. Mesenteric venous thrombosis may be an
indication for a multivisceral transplant rather than a liver transplant alone.
Portal vein thrombosis in the presence of hepatoma is often due to vascular
invasion which precludes liver transplantation.
Hepatic artery anatomy, patency and identification of anomalies is important. If the recipient
artery is small or thrombosed, it may be necessary to do a jump graft from the
recipient’s aorta, so the presence or absence of aortic disease is assessed –
it is too late to discover an aortic aneurysm once the liver has been removed.
Evaluating comorbidity
Cardiovascular disease can be difficult to assess. Most liver failure patients have limited
exercise tolerance and their vasodilated state, a consequence of liver failure,
tends to offload the heart, so masking possible cardiac disease.
Echocardiography and stress testing are performed where concern exists.
Portopulmonary hypertension (pressure >25 mmHg) may be
suggested on echocardiography. If so, it is confirmed by direct measurement.
Severe portopulmonary hypertension (mean pulmonary arterial pressure [MPAP]
>50 mmHg) constitutes a contraindication to liver transplantation,
Diabetes is common in
patients with chronic liver disease, particularly hepatitis C and non-alcoholic
fatty liver disease (NAFLD), and may contribute to cardiovascular disease.
Chronic renal disease has a significant impact on outcome and requires careful assessment.
Combined liver and kidney transplant may be preferred in carefully selected
patients to improve post- operative outcome.
Respiratory assessment with pulmonary function testing and blood gas analysis is necessary to
evaluate any associated lung disease – smoking and alcohol are common
bedfellows. Hypoxic patients with hepatopulmonary syndrome due to arteriovenous
shunting through the lungs require careful study – high levels of shunting
preclude transplantation because adequate oxygenation may not be possible
post-operatively. An arterial pO2 <50 mmHg on room air is a
contraindication to transplantation.
Oropharyngeal examination is appropriate in patients with a history of alcohol intake and smoking;
oropharyngeal (and oesophageal) cancers are common in this group and easily
missed.
Psychiatric evaluation is important where substance misuse has occurred (e.g. alcohol-related
liver disease or prior intravenous drug misuse), with particular attention paid
to ensuring that adequate support services are in place for the patient in the
post-operative period. Such support can minimise the chances of return to
alcohol consumption or illicit drug use, which can have a negative impact on
patient and graft survival post-transplantation.
