Biliary Atresia: Pathogenesis and Treatment

ABSTRACT

Biliary atresia is a disorder of infants in which there is obliteration or discontinuity of the extrahepatic biliary system, resulting in obstruction of bile flow. Untreated, the resulting cholestasis leads to progressive conjugated hyperbilirubinemia, cirrhosis, and hepatic failure. Biliary atresia has an incidence of approximately one in 10,000 live births worldwide. Evidence to date supports a number of pathogenic mechanisms for the development of biliary atresia. An infectious cause, such as by a virus, would seem most pausible in many cases. The clinical observation that biliary atresia is rarely encountered in premature infants would support an agent acting late in gestation. However, no infectious or toxic agent has been conclusively implicated in biliary atresia. Genetic mechanisms likely play important roles, even regarding susceptibility to other specific causes, but no gene whose altered function would result in obstruction or atresia of the biliary tree has been identified. The variety of clinical presentations support the notion that the proposed mechanisms are not mutually exclusive but may play roles individually or in combination in certain patients.

Biliary atresia, when untreated, is fatal within 2 years, with a median survival of 8 months. The natural history of biliary atresia has been favorably altered by the Kasai portoenterostomy. Approximately 25 to 35% of patients who undergo a Kasai portoenterostomy will survive more than 10 years without liver transplantation. One third of the patients drain bile but develop complications of cirrhosis and require liver transplantation before age 10. For the remaining one third of patients, bile flow is inadequate following portoenterostomy and the children develop progressive fibrosis and cirrhosis. The portoenterostomy should be done before there is irreversible sclerosis of the intrahepatic bile ducts. Consequently, a prompt evaluation is indicated for any infant older than 14 days with jaundice to determine if conjugated hyperbilirubinemia is present. If infectious, metabolic, endocrine disorders are unlikely and if the child has findings consistent with biliary atresia, then exploratory laparotomy and intraoperative cholangiogram should be done expeditiously by a surgeon who has experience doing the Kasai portoenteostomy. Biliary atresia represents the most common indication for pediatric liver transplantation, representing more than 50% of cases in most series. Transplantation is indicated when symptoms of end stage liver disease occur, including recurrent cholangitis, progressive jaundice, portal hypertension complications, ascites, decreased synthetic function, and growth/nutritional failure.

KEY WORDS

biliary atresia - pathogenesis - outcome