Alagille syndrome is a genetic condition in which a person has fewer than the normal number of small bile ducts inside the liver. Bile ducts, also called hepatic ducts, are tubes that carry bile from the liver cells to the gallbladder and eventually drain into the small intestine. Bile is a liquid produced in the liver that serves two main functions: carrying toxins and waste products out of the body and helping the digestion of fats and the fat-soluble vitamins A, D, E, and K. The decreased number of hepatic ducts causes bile to build up in the liver, leading to liver damage. Eventually the liver may stop working and a liver transplant is necessary.