"Up to 85% of CBD stones are secondary from GB. Primary CBD stones are caused by conditions leading to bile stasis and chronic bactibilia. Up to 90% of patients with brown pigment CBD stones have bile culture results positive for bacteria. Primary duct stones are usually brown pigment stones. Brown stones differ from black pigment stones by having a higher content of cholesterol . In Western population Biliary stasis is secondary to factors such as sphincter of Oddi dysfunction, benign biliary strictures, sclerosing cholangitis, and cystic dilatation of the bile ducts. Bile stasis promotes growth of bacteria, which produce phospholipase A1, thus releasing fatty acids from biliary phospholipids. The duct epithelium and/or bacteria (eg, Escherichia coli) produce beta-glucuronidase in amounts sufficient to deconjugate bilirubin diglucuronide. The presence of free fatty acids, deconjugated bilirubin, and bile acids leads to the formation of insoluble calcium bilirubinate particles. With the loss of bile acids, cholesterol becomes insoluble, resulting in the formation of biliary sludge. The sludge also contains mucin and bacterial cytoskeletons, which further aid in stone formation. In Asian populations, infestation with A lumbricoides and C sinensis may promote stasis by either blocking the biliary ducts or by damaging the duct walls, resulting in stricture formation. Bactibilia is also common in these instances, probably secondary to episodic portal bacteremia. Some authors have suggested that the stones are formed because of the bactibilia alone and that the parasites' presence is just a coincidence. "
Case By Dr MGK Murthy, Sr Consultant Radiologist