Entericobiliary fistulas represent a complication of cholelithiasis or choledocholithiasis. Cholecystoduodenal fistulas are the most common type, followed by cholecystocolic and choledochoduodenal fistulas.

Distal small bowel obstruction from an impacted ectopic gallstone, called gallstone ileus, is an unusual complication of chronic cholecystitis and affects only a minority of patients with cholecystoduodenal fistulas. Gallstones that result in intestinal obstruction typically exceed 2 cm in diameter.

Pneumobilia suggests the presence of an internal biliary fistula in the absence of prior
sphincterotomy, surgical bypass procedure, recent endoscopic retrograde cholangiopancreatography, or passed common duct stone.