A biliary fistula is a type of fistula in which bile flows along an abnormal connection from the bile ducts into nearby hollow structure. Types of biliary fistula include: * bilioenteric fistula: abnormal connection to small bowel, usually duodenum. * thoracobiliary fistula: abnormal connection to pleural space or bronchus (rare). These may be contrasted to a bile leak, in which bile escapes the bile ducts through a perforation or faulty surgical anastomosis into the abdominal cavity. Damage to a bile duct may result in a leak, which may eventually become a biliary fistula.