Cystic duct entry--another cause of pseudocalculus.

Certain pitfalls face the endoscopist during ERC in the diagnosis of common bile duct stones. False-positive filling defects for calculi may be caused by air bubbles, blood clot, tumor, and the pseudocalculus sign of the lower common bile duct (CBD) due to sphincter spasm. Another false positive may be encountered by the presence of a filling defect at the confluence of the cystic duct and common bile duct, and we report on three such cases. The cause of this pseudocalculus sign of the mid-CBD is not clear. We speculate that it may arise as a result of an unopacified jet of bile flowing from the cystic duct displacing contrast in the CBD.