PREDICTING COMMON BILE-DUCT LITHIASIS - DETERMINATION AND PROSPECTIVE VALIDATION OF A MODEL PREDICTING LOW-RISK

BACKGROUND: The aim of this two-part prospective study was: (1) to identify simple, noninvasive, preoperative factors associated with low or very low risk of common bile duct lithiasis (CBDL); and (2) to test the validity of the statistical model obtained during Part One by the postcholecystectomy follow-up of patients classified into a low-risk group. PATIENTS AND METHODS: In Part One of the study, preoperative clinical, biologic, and ultrasonographic data, and intraoperative cholangiographic findings were collected from 503 consecutive patients undergoing cholecystectomy for symptomatic lithiasis from 1985 to 1989. Using the data obtained in Part One, a linear logistic model was used prospectively in Part Two to determine the prediction of absence of CBDL in 279 consecutive patients. No jaundice, normal transaminase levels, common bile duct (CBD) diameter <8 mm, and no intrahepatic duct enlargement defined the low-risk group of CBDL. RESULTS: In Part One, CBDL was present in 84 (17%) of all patients. Five parameters were used to classify 73% of all patients as low risk of CBDL and 27% as high risk. In the low-risk groups, CBDL was present in 1% of 116 cases with acute gallbladder complications, and 5% of 250 cases with no acute gallbladder complications. In Part Two, 171 (61%) patients were classified in the low-risk group (Group 1), and CBD stones were not sought by any additional preoperative investigations or intraoperative cholangiography (IOC). One hundred eight patients (39%) were considered at risk of CBDL (Group 2). Mean follow-up was 20.6 months (median 19); 2 patients (1%) in the low-risk group presented a symptomatic retained stone. CONCLUSIONS: This study validated this simple model for predicting risk of CBDL and avoiding invasive preoperative investigations-as well as IOC-in more than 60% of symptomatic cholelithiases. In addition, this model seemed useful for defining patients in whom further exploration for CBDL was justified, since 42 (39%) of the 108 Group 2 patients were proved to have CBDL.