Pre-operative ultrasound measurement of bile duct diameter: basis for selective cholangiography.

In this prospective study, prior to cholecystectomy, the diameter of the common hepatic duct was measured; duct size was then compared with probability of finding stones at operation. Of 115 patients entering the study, 36 had stones removed from the common duct at the time of cholecystectomy but only three (8%) were demonstrated by ultrasonography. No stones were found in ducts less than or equal to 3 mm in size (31% patients). Only two of 26 patients with ducts measuring 4 mm had stones. As duct size increased, so did the probability of stones and all patients with ducts greater than or equal to 9 mm in diameter had stones. It is concluded that pre-operative ultrasound provides a reliable basis for a policy of selective cholangiography.