Brown pigment gallstones differ from cholesterol stones in their pathogenesis. The formation of brown pigment stones is most directly promoted by:

• A Bacterial deconjugation of soluble conjugated bilirubin by beta-glucuronidase in obstructed, infected bile ✓
• B Supersaturation of bile with unconjugated bilirubin secondary to chronic hemolysis
• C Excess biliary cholesterol relative to bile salts and lecithin
• D Mucin hypersecretion driven by prostaglandin E2 in the gallbladder wall

Explanation

Brown pigment stones form in intrahepatic and extrahepatic ducts where bacterial infection and stasis allow bacteria such as E. coli to release beta-glucuronidase, which deconjugates bilirubin glucuronides into insoluble unconjugated bilirubin that precipitates with calcium. Option B describes black pigment stones, which form in the gallbladder in chronic hemolysis or cirrhosis without infection. Options C and D are mechanisms of cholesterol stone formation, not pigment stones.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.