<prompt> Air in biliary tract is seen in all, Except:Gall stone ileusSclerosing cholangitisCarcinoma gall bladderEndoscopic papillotomy  <response>: Ans. is b Sclerosing cholangitis Ref. Sutton Radiology, 6e, p. 957.First go through the causes of air in billary tract:Following surgery or endoscopic intervention on biliary tract.Gall stone fistulaMalignant fistulaPhysiological lax sphincterPerforation of peptic ulcer in biliary tract.Now lets see why option b is to be preferred.Option aGall stone ileus is obvious to everyone.Option cCarcinoma gall bladder can cause air in biliary tract by forming malignant fistulae.Option dEndoscopic papillotomy- Any operation on biliary tract can cause air in biliary tract, moreover endoscopic papillotomy can lead to lax sphincter. 