Pseudotumor of the distal common bile duct at endoscopic retrograde cholangiopancreatography

Background: Prior studies have described a pseudocalculus appearance in the distal common bile duct as a normal variant at cholangiography. The objective of this study was to describe the occurrence of pseudotumor in the distal common bile duct at endoscopic retrograde cholangiopancreatography (ERCP). Methods: Nine patients who underwent ERCP between May 2004 and July 2008 were identified as having a transient eccentric mural-based filling defect in the distal common bile duct. A single reader systematically reviewed all studies and recorded the imaging findings. Results: The mean diameter of the filling defect was 9 mm (range, 5 to 11). Eight patients had resolution of the filling defect during the same ERCP or on a subsequent ERCP, and in two of these patients the inferior border of the filling defect was not well visualized. The other patient underwent surgical resection of a presumed tumor with no evidence of malignancy on surgical pathology. Conclusion: An eccentric mural-based filling defect in the distal common bile duct can be artifactual in nature and may reflect transient contraction of the sphincter of Oddi. Recognition of this pseudotumor may help avoid unnecessary surgery.