This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
Pneumobilia is seen in 
Select and explain. 
A. Gallstone ileus, B. TPN, C. Volvulus, D. Ruptured hydatid cyst
A: Gallstone ileus
Answer: A: Gallstone ileus 
Explanation: Causes of pneumobilia Previous surgery (papillotomy, choledochojejunostomy, ERCP with sphincterectomy) Gallstone ileus Emphysematous cholecystitis Choledochoduodenal or cholecystocolic fistula Tracheobiliary fistula Suppurative cholangitis Mirriz's syndrome (Due to cholecystoenteric fistula) Ref: Sabiston 20th edition Pgno :1570