Brown pigment stones in the common bile duct: Reduced bilirubinate diconjugate in bile

Background: Bilirubin is the main component of most common bile duct stones . Normally, almost all bilirubin in bile is conjugated to glucuronic acid o r some other sugar moiety. These conjugates are unstable and liable to deco njugation. Unconjugated bilirubin is insoluble and may precipitate as the c alcium salt found in brown pigment stones. The pattern of bilirubin conjuga tes in common duct bile of patients with choledocholithiasis has been unkno wn. Methods: In a clinical series of 55 patients with choledocholithiasis c ommon-duct bile was aspirated, and the bibirubin conjugates analyzed with h igh-performance liquid chromatography. One stone from each patient was anal yzed fur cholesterol and bilirubin content to determine stone type. Results : Sixteen patients had cholesterol stones, 38 patients had brown pigment st ones, and 1 patient had a black; stone. Patients with pigment stones had a lower percentage of bilirubin diglucuronide (median, 60.3%; interquartile r ange. 49.7%-67.3%) than patients with cholesterol stones (64.0%; 60.2%-73.3 %) (Mann-Whitney, P = 0.015). No significant difference was round for the o ther bilirubin conjugates, total bilirubin, or biliary pH when pigment and cholesterol stone patients were compared. The time of bile sampling in rela tion to papillotomy and treatment of cholestasis was not associated with th e low percentage of bilirubin diglucuronide. The observation of reduced val ues for bilirubin diglucuronide could not be ascribed to duodenal diverticu la or Billroth-II gastric resection. Conclusion: The percentage of the main bilirubinate conjugate. bilirubin diglucuronide, is decreased in the commo n duct bile of patients with pigmented compared with cholesterol stones.