Pseudocalculus sign (common bile duct)

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The pseudocalculus sign is a term coined to describe a mimic of a distally impacted common bile duct (CBD) stone on ERCP, MRCP and the various forms of cholangiography, including T-tube, CT, intraoperative, and percutaneous .

It results from the forceful contraction of the choledochal sphincter (of Oddi) at the ampulla of Vater with pouting into the lower end of the CBD. This impression is superiorly rounded imitating the superior surface of a stone, potentially leading to the misdiagnosis of choledocholithiasis.

Findings that support diagnosis of pseudocalculus rather than true calculus:

the inferior margin of the pseudocalculus will never be seen as it is not a true filling defect; if an inferior margin is visualized then pseudocalculus has been excluded
the pseudocalculus usually resolves with application of IV/IM glucagon which relaxes the choledochal sphincter
pseudocalculus will not impede the passage of contrast medium/bile nor be associated with abdominal pain
pseudocalculus lacks any calcification

The sign was first reported in 1968 by the renowned GI radiologist Thomas C Beneventano (1932-1988) who spent his entire career at the Albert Einstein College of Medicine in New York City .