Despite advances in the treatment of chronic liver disease (most notably viral hepatitis), cirrhosis remains the twelfth most frequent cause of death in the United States and results in 33,539 deaths annually.1 Only a fraction of the individuals with advanced liver disease benefit from liver transplantation (LT), with approximately 7000 recipients per annum. Although innovations such as living and split donor transplantation have modestly enhanced transplant rates, only a substantial increase in the deceased donor pool will increase transplant activity. Currently, 17,000 people await LT, with more than 1500 wait-listed patients dying annually. The Model for End-Stage Liver Disease (MELD) score, an objective method adopted in 2002 for organ allocation in the United States, has resulted in a reduction of deaths on the waiting list. Despite the continuing debate about its application in some circumstances [e.g., hepatocellular carcinoma (HCC)], the MELD score has stood the test of time as an equitable system for the distribution of a scarce resource.
Indications (Table 1)
The commonest indication for LT in adults is decompensated cirrhosis, which in turn reflects the most frequent etiologies of chronic liver disease (Fig. 1); these include chronic hepatitis C virus (HCV), alcohol, cholestatic disease, and fatty liver disease. Another prominent indication for LT is small, nonresectable HCC.
|Chronic noncholestatic liver disorders|
|Chronic hepatitis B|
|Alcoholic liver disease|
|Cholestatic liver disorders|
|Primary biliary cirrhosis|
|Primary sclerosing cholangitis|
|Nonsyndromatic paucity of intrahepatic bile ducts|
|Progressive familial intrahepatic cholestasis|
|Metabolic disorders causing cirrhosis|
|Nonalcoholic steatohepatitis and cryptogenic cirrhosis|
|Glycogen storage disease type IV|
|Metabolic disorders causing severe extrahepatic morbidity|
|Urea cycle defects|
|Disorders of branch chain amino acids|
|Primary malignancies of the liver|
|Fulminant hepatic failure (ALF)|
|Metastatic neuroendocrine tumors|
Importantly, even though most adult LT recipients have cirrhosis in the absence of complications, its diagnosis does not imply a need for transplantation. Some simple clinical details, such as the presence of varices, ascites, infection, or renal failure, provide useful prognostic information for the patient with cirrhosis3 (Table 2). A referral for LT should be considered when a patient with cirrhosis experiences an index complication such as ascites, variceal hemorrhaging, or hepatic encephalopathy that cannot be managed medically or when the MELD score of a patient with declining hepatocellular function approaches 15 (Fig. 2). Importantly, a stable patient with cirrhosis can deteriorate quite precipitously once a major complication such as variceal hemorrhaging supervenes. However, acute decompensation in a previously stable patient with cirrhosis can often respond to prompt medical therapy, such as the control of variceal hemorrhaging via endoscopic banding with other measures, including antibiotic prophylaxis. Implicit in the decision to initiate an LT evaluation is an absence of effective medical therapy (e.g., corticosteroids for autoimmune hepatitis) or a reversible component in hepatic decompensation (e.g., continued alcohol use). Although LT is unequivocally beneficial for recipients with advanced liver disease, the introduction of the MELD score (http://optn.transplant.hrsa.gov/resources/MeldPeldCalculator.asp?index=98) has helped define which patients should undergo transplantation.4 Recipients undergoing LT with a MELD score less than 15 had significantly higher 1-year mortality in comparison with candidates with similar disease severity who remained on the waiting list. A transplant survival benefit was unequivocally observed at MELD scores of 18 and higher, with the magnitude progressively increasing with higher MELD scores5 (Fig. 3).
|Stage of Cirrhosis||Criteria||Prognosis: Mortality/Year (%)|
|1||Compensated, no varices||1|
|5||Infections and renal failure||67|
HCC has become a prominent indication for LT, and this reflects not only its rising incidence but also the enhanced priority for organ allocation for HCC within the Milan criteria. Currently, nearly 20% of adult transplants in the United States are performed for HCC. Nearly half of these (9.9% of the overall total) reflect the allocation of 22 MELD points for potential recipients within the Milan criteria (i.e., a single HCC ≤ 5 cm or up to three tumors, none > 3 cm, without vascular invasion, regional node involvement, or distant metastases).6 Continued areas of controversy include downsizing larger tumors with chemoembolization to fit these criteria because, in comparison with tumor size alone, tumor biology more accurately reflects the risk of HCC recurrence.7 A report from the University of California San Francisco suggested that recipients with a solitary HCC up to 6.5 cm or with up to three lesions, the largest of which was ≤4.5 cm with the sum of the diameters no larger than 8 cm, had outcomes similar to those of patients meeting the Milan criteria.8 However, expansion beyond the Milan criteria for extra MELD points has not been generally accepted, and this reflects continued uncertainty about the role of LT with a more extensive tumor burden.
Hepatopulmonary syndrome is another complication of cirrhosis that is potentially eligible for extra MELD points because LT can favorably alter its course. Potential recipients must have an arterial oxygen tension less than 60 mm Hg on room air without underlying lung disease to receive these points. However, patients with HPS who have an arterial oxygen tension less than 50 mm Hg alone or in conjunction with a preoperative shunt fraction greater than 20% were 7.5 times as likely to experience perioperative mortality.9 Portopulmonary hypertension is another important extrahepatic complication of cirrhosis. Potential recipients suffering from portopulmonary hypertension with a mean pulmonary artery pressure greater than 35 mm Hg despite vasodilator therapy are usually not candidates for transplantation because of the magnitude of the perioperative and postoperative risk of cardiopulmonary complications. Acute liver failure (ALF) is defined as severe liver injury with encephalopathy and coagulopathy [international normalized ratio (INR) > 1.5] in a patient without preexisting cirrhosis and with an illness of less than 26 weeks' duration. ALF has a variable prognosis depending on the etiology and the likelihood of spontaneous recovery. The acknowledgment of the rapidly progressive course of ALF and its high mortality rate has led to its prioritization for LT if specific criteria are met.
Key components of the evaluation for LT include an assessment by a transplant hepatologist and surgeon to confirm that the patient's liver disease is of such severity that LT is reasonable and feasible and that other therapeutic options have been exhausted. A comprehensive medical assessment is undertaken to exclude important comorbidities such as coronary artery disease (Table 3). Once these consultations and investigations are complete, the patient's candidacy is discussed at a formal patient selection meeting. If the patient is accepted and financial clearance is obtained, the patient can be listed to wait for a donor organ for transplantation.
|Anatomical abnormality precluding LT|
|Acquired immune deficiency syndrome|
|Advanced cardiac or pulmonary disease|
|Ongoing alcohol/illicit drug use|
|Extensive thrombosis involving superior mesenteric vein and portal vein|
|ALF with intracranial pressure > 50 mm Hg or cerebral perfusion pressure < 40 mm Hg|
|Lack of psychosocial support|
|Human immunodeficiency virus|