Which of the following statements about choledocholithiasis are correct?

A. Common duct stones can originate in the gallbladder and migrate to the common duct, and stones can form de novo in the duct system

B. Calcium bilirubinate stones are associated with the presence of bacteria in the duct system.

C. Common duct stones discovered at laparoscopic cholecystectomy should be treated by postoperative endoscopic extraction.

DISCUSSION: Most common duct stones originate in the gallbladder and migrate to the common duct, where they may become larger. These stones tend to consist predominantly of cholesterol (about 80% of gallbladder stones are predominantly cholesterol). Stones found in the bile ducts after cholecystectomy may have been overlooked, but de novo stone formation does occur. Arbitrarily, stones found 2 years after cholecystectomy are assumed to have formed within the duct system. Calcium bilirubinate stones are thought to result from precipitation of insoluble bilirubin monoglucuronide formed by deconjugation of bilirubin diglucuronide, a reaction promoted by the enzyme betaglucuronidase, which is produced by bacteria in the biliary tract. Calcium bilirubinate stones are found almost exclusively in patients who have some form of biliary tract lesion that causes partial obstruction, and these patients tend to have bactibilia. Stones smaller than approximately 5 mm. often can be extracted through a dilated cystic duct or pushed into the duodenum. Larger stones are best left for postoperative endoscopic sphincterotomy and extraction. Patients with more than five stones or stones larger than 1.5 cm. should be treated by open choledocholithotomy or, when indicated, a biliary-enteric anastomosis. Not all patients with symptomatic common duct stones have elevated serum bilirubin, but when jaundice is present the bilirubin is only rarely greater than 15 mg. per dl.