Biliary Atresia

Biliary atresia is a progressive fibro-obliterative cholangiopathy of infancy. The extrahepatic bile ducts—and often portions of the intrahepatic ducts—become inflamed, scarred, and obstructed. Bile cannot reach the intestine, so it accumulates in the liver and damages the portal tracts. Without effective drainage, fibrosis advances to biliary cirrhosis and liver failure. This obstruction explains the characteristic combination of findings. Conjugated bilirubin backs up into the bloodstream and, because it is water soluble, is excreted in urine, making the urine dark. Bile pigments no longer reach the intestine, so stools become pale, clay-colored, or acholic. Reduced bile in the intestine also impairs fat digestion and absorption, leading to deficiency of vitamins A, D, E, and K and contributing to poor growth. The infant may look surprisingly well at first. Feeding can remain normal while liver injury is already progressing. Untreated biliary atresia is fatal, and the condition is the leading indication for liver transplantation in children.