If a pancreatic tumor is so small that it does not show up on spiral ct, what are the odds that this would cause bile duct obstructions?

Very low: Pancreatic cancers commonly arise in the head of the pancreas and thus present with obstructive jaundice. This is caused by extrinsic compression of the common bile duct(cbd). However, some of these tumors can originate in the periampullary area where they may not show well on a ct scan and need upper endoscopy and ERCP to be visualized/localized.

Non: pancreatic Ca develops in the ductal system over 15-20 yrs Then invasion thru the wall of the duct will begin but jaundice will not occur. Approx 1/2 cm below the pancreatic duct is a groove in the head of the pancreas beginning at the top and extending the full width. Here the bile duct runs from liver to duodenum. As tumor grows it eventually reaches the groove to obstruct the duct.