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.