Analysis of the signs of common bile duct obstruction at percutaneous transhepatic cholangiography.

The radiological signs of common bile duct obstruction have been analysed in a series of 146 Chiba needle percutaneous cholangiograms. The upward pointing convexity was the most reliable sign, indicating impacted stones in all cases. The least reliable sign was the biconcave caudal cut-off. An inter-observer variation study of the signs indicated that a knowledge of the clinical history did not improve the diagnostic accuracy of film reading.