Prediction of common bile duct stones prior to cholecystectomy: a prospective validation of a discriminant analysis function.

BACKGROUND Selection routines for preoperative endoscopic retrograde cholangiopancreatography (ERCP) in patients with symptomatic gallstone disease should give a low frequency of both false-negative ERCP results and residual common bile duct stones (CBDS). OBJECTIVE To validate a discriminant function (DF) based on retrospectively collected data, for characterization of patients with symptomatic gallstone disease as regards presence of CBDS, and to compare clinical, ultrasonographic, and DF characterization. DESIGN Prospective registration of CBDS criteria in consecutive patients with symptomatic gallstone disease. SETTING A department of surgical gastroenterology in a Norwegian central hospital. PATIENTS One hundred ninety-two patients with gallbladder stones. INTERVENTION Laparoscopic cholecystectomy or ERCP with or without endoscopic sphincterotomy. MAIN OUTCOME MEASUREMENTS Sensitivity and specificity of the clinical, ultrasonographic, and DF characterizations, and test of the validity of the DF. RESULTS Thirty-two patients had CBDS. The clinical criteria of CBDS were present in 152 patients (79.2%): 21.1% of these patients had CBDS and there were no false-negative results (sensitivity, 100%; specificity, 25%). The risk of CBDS in patients with normal bile ducts at ultrasonographic examination was 8 of 124, and in patients with dilated ducts or suspected CBDS, 17 of 47 (sensitivity, 68%; specificity, 80%). The DF was positive in 50 patients (26%): 60% of these had CBDS, and there were 2 false-negative results (sensitivity, 94%; specificity, 88%). A discriminant analysis of the prospectively registered data selected the same set of CBDS criteria, and a new DF did not alter the characterization of any patient. CONCLUSIONS Clinical characterization had a higher sensitivity for CBDS detection than ultrasonography alone, but a lower specificity. The DF analysis was both more sensitive and specific than ultrasonography, and seemed efficient in selecting symptomatic gallstone patients for ERCP. It was reproducible and simple to use.