Pseudocalculus sign. A pitfall of static cholangiography.

The pseudocalculus formation was first noted by Caroli in 1960, and was first called a sign by Beneventano and Schein in 1968. It is a cholangiographic illusion that appears as a filling defect in the distal common bile duct when static or "spot" films are exposed during the contractile phase of choledochal sphincter activity. Although first noted and most frequently seen in T-tube cholangiography, it is seen also during intravenous and intraoperative cholangiography. Because it mimics radiographically an impacted stone in the distal common bile duct, its delineation is critical to avoid unnecessary instrumentation of the common bile duct or even reoperation. In this review the authors discuss briefly the anatomy and physiology of the distal common bile duct and the etiology, differential diagnosis, and recognition of the pseudocalculus sign.