Can ERCP contrast agents cause pseudomicrolithiasis? Their effect on the final outcome of bile analysis in patients with suspected microlithiasis

Background: Microlithiasis has been implicated in the etiology of idiopathi c pancreatitis and biliary-type pain in patients with intact gallbladders. Contrast injection at endoscopic retrograde cholangiopancreatography (ERCP) is used to confirm access into the bile duct and bile is also aspirated to look for microlithiasis. It is not known whether contrast agents contain c rystals that could mimic true microlithiasis. Methods: Four mt of 2 contrast agents (Hypaque and Omnipaque) were examined after centrifugation under polarizing microscopy. In the second part of th e study, bile aspirated during ERCP with contrast injection was examined fo r microlithiasis and contrast pseudomicrolithiasis. Results: Contrast agents exhibited pseudomicrolithiasis that mimicked calci um bilirubinate granules. Pathologists participating in the study were not aware of contrast pseudomicrolithiasis. Nine of twelve (75%) patients would have been reported as having microlithiasis and would possibly have underg one an unnecessary cholecystectomy. Conclusion: When bile collected during ERCP is to be examined for microlith iasis, it should be collected without contamination by a contrast agent. If this is not possible, pathologists should be aware that contrast can cause pseudomicrolithiasis.