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.
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.