Prospective evaluation of ultrasonography and liver function tests for preoperative assessment of the bile duct.

Current means of predicting the presence of bile duct stones are sensitive but produce a large number of false-positive results, potentially leading to added morbidity from unnecessary invasive investigation. This study prospectively assessed 545 patients with gallbladder stones, including 55 patients with bile duct stones, to refine criteria for further investigation of the bile duct. The sensitivity, specificity, and positive and negative predictive values were calculated for bile duct dilatation (diameter abnormal if larger than 5 mm below age 50 years, normal value increasing by 1 mm per decade) and elevation of three liver function tests, singly or in combination. Depending on the number of abnormalities used the sensitivity ranged from 46 to 96 per cent and the positive predictive value from 35 to 77 per cent. All groupings gave at least 96 per cent negative predictive value for the absence of stones but none combined both high sensitivity and positive predictive value. The specificity was improved if the tests were done on the working day before operation. Refining criteria for predicting bile duct stones allows the selective use of cholangiography and may reduce the number of negative cholangiograms.