This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Air in the biliary tract is seen in all except – 
Select and explain. 
A. Gall stone ileus, B. Sclerosing cholangitis, C. Carcinoma gall bladder, D. Endoscopic papillotomy
B: Sclerosing cholangitis
Answer: B: Sclerosing cholangitis 
Explanation: Gallstone ileus, carcinoma gall bladder and endoscopic papillotomy can cause pneumobilia (air in biliary tract)
Ascending cholangitis (not sclerosing cholangitis) can cause pneumobilia.