Detection of choledocholithiasis: comparison of unenhanced helical CT and endoscopic retrograde cholangiopancreatography

PURPOSE: To compare unenhanced helical computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP) in the detection of common bile duct calculi. MATERIALS AND METHODS: Within 13 months, 51 patients (aged 18-94 years) with clinically suspected choledocholithiasis underwent unenhanced helical CT immediately before undergoing ERCP. CT scans were evaluated for the presence of bile duct stones, ampullary stones, the gallbladder and gallbladder stones, intrahepatic biliary dilatation, and the size of the bile duct at the porta hepatis and in the pancreatic head. ERCP images were evaluated for the presence of bile duct or ampullary stones, as well as for biliary dilatation. RESULTS: Unenhanced helical CT depicted common bile duct stones in 15 of 17 patients found to have stones at ERCP. Three patients had stones impacted at the ampulla, all of which were detected with CT. In addition, there was one false-positive finding at CT. CT had a sensitivity of 88%, a specificity of 97%, and an accuracy of 94% in the diagnosis of common bile duct stones. CONCLUSION: Unenhanced helical CT is useful for evaluating suspected choledocholithiasis.