<prompt> All of the following are known predesposing factors for cholangiocarcinoma except :CBD stonesClonorchis sinensisUlcerative colitisPrimary sclerosing cholangitis  <response>: Answer is A CBD stone : Cholelithiasis is not clearly a predisposing factor for Cholangiocarcinoma - Harrison The predisposing factors of cholangiocarcinoma include : I. Chronic hepato-biliary parasite infection Clonorchiasis or Asiatic cholangio-hepatitis Q Congenital Anomaly with ectatic ducts Choledochal cyst.Q Sclerosing cholangitis Q Ulcerative colitis Occupational exposure to carcinogensQRubber Automotive plants Note: Nodular lesions that arise at the bifitrcation of hepatic ducts are called Klastskin tumors. Q 