Biliary Atresia

Biliary Atresia

Also read: Bile duct stricture

A Developmental defect of the Bile Ducts
Biliary Atresia is a defect in the development of the bile ducts that drain from the liver into the intestines that is characterized by obliteration of the biliary system, resulting in obstruction to bile flow. The disorder represents the most common surgically treatable cause of jaundice encountered during the newborn period. However due to lack of timely diagnosis, secondary biliary cirrhosis or scarring of the liver invariably results (Over ten babies are reviewed each year at the author's center with liver failure secondary to BA that was not treated on time nearly 5 babies have been transplanted here for secondary biliary cirrhosis). Patients with biliary Atresia have two distinct type of defects. The post natal form with isolated biliary Atresia that accounts for 65 - 90% of cases, and the fetal/embryonic form that is associated with situs inversus or polysplenia/asplenia with or without other congenital anomalies that accounts for 10 - 35% of cases.

The pathological types of the defect are as follows-

1. Type 1 involves obliteration of the common duct, while the proximal ducts are patent;
2. Type II is characterized by Atresia of the hepatic duct, with cystic structures found in the porta-hepatis;
3. And type III (> 90% of patients) involves Atresia of the right and left hepatic ducts at the level of the portal hepatis. (these variants can be easily confused with intrahepatic biliary hypoplasia, which is essentially a disorder that cannot be rectified surgically)

Why does it happen?

The pathogenesis of this disorder remains poorly understood, though histopathologic features of biliary Atresia have been studied extensively in surgical specimens. Early studies postulated a congenital malformation of the biliary ductular system. The fetal/embryonic form of Atresia that is associated with other congenital anomalies is likely to be due to a birth defect. However the more common neonatal type has fair degree of progressive inflammatory lesion, suggesting a role for infectious and/or toxic agents that may cause bile duct obliteration.

Ducts within the liver, extending to the portal hepatis, are initially patent in the most prevalent type III histopathological variant during the first few weeks of life but may progressively be destroyed by the same agent(s) that damaged the extrahepatic ducts and by the effects of retained toxins in bile. This suggests that extrahepatic biliary Atresia is most likely an acquired lesion. However, to date, no single etiologic factor has been identified. Infectious agents seem to be the most plausible candidates, particularly in the isolated (neonatal) form of Atresia. Retroviruses and other viruses, including rotavirus and cytomeglaovirus (CMV) have also been implicated as causative agents.