A 12-year-old boy with hereditary spherocytosis undergoes cholecystectomy for recurrent biliary colic. The gallbladder contains multiple small, jet-black, friable stones that are non-radiopaque. These stones are composed chiefly of:

• A Cholesterol monohydrate crystals
• B Calcium carbonate
• C Calcium bilirubinate ✓
• D Mixed cholesterol and bile salts

Explanation

Black pigment stones form when unconjugated bilirubin concentration rises in bile, as in chronic hemolysis such as hereditary spherocytosis. The excess unconjugated bilirubin precipitates as calcium bilirubinate polymers, producing small, hard, black, spiculated stones that are typically non-radiopaque. Brown pigment stones also contain calcium salts of fatty acids but occur in infected bile and are associated with parasites and bacteria, not hemolysis. Cholesterol stones are yellow to white and account for about 80 percent of stones in Western populations.

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.