Chemical composition of common bile duct stones.

The common bile duct stones obtained from 148 patients were analysed chemically for cholesterol, calcium and bilirubin. When stones were present in both the common bile duct and gallbladder at the time of surgery, the common duct stones were similar in chemical composition to gallbladder stones in the majority of cases and were predominantly cholesterol-type stones. However, common bile duct stones from patients whose gallbladders had been removed at least one year before the detection of common duct stones contained less cholesterol and more bilirubin than common bile duct stones which were associated with gallbladder stones. Thirty per cent of these stones contained suture material in the centre of the stone. Overall, the results indicate that common bile duct stones are more likely to be pigment type than gallbladder stones, especially if the common duct stones are large, have formed in the duct and become symptomatic less than 12 years after cholecystectomy. Non-absorbable suture material should be avoided in surgery involving the common bile duct.