A 22-year-old man with hereditary spherocytosis undergoes cholecystectomy for recurrent biliary colic. The stones recovered are small, jet black, and friable. The chief component of these stones is:

• A Calcium bilirubinate derived from unconjugated bilirubin ✓
• B Cholesterol monohydrate crystals
• C Calcium carbonate precipitates
• D Bile acid polymers

Explanation

Black pigment stones form when chronic hemolysis increases bilirubin production, raising the load of unconjugated bilirubin that solubilizes poorly and complexes with calcium as bilirubinate. They are seen in hereditary spherocytosis, sickle cell disease, and ineffective erythropoiesis. The best distractor is cholesterol, which forms radiolucent stones by a different pathway unrelated to hemolysis.

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.