The purpose of the bile ducts is to transport bile from the liver to the small intestine, where it helps to digest food.

An infant with biliary atresia is born with malformed bile ducts. The ducts fail to form correctly during development in the womb.

In an infant with biliary atresia, the bile does not pass into the intestine. If the bile ducts are blocked then the bile backs up into the liver and causes damage to the liver. Eventually, the bile in the liver causes the bilirubin level to rise in the bloodstream, resulting in jaundice.