A 20-year-old man presents with painless recurrent gross hematuria. His father carries sickle cell trait. Hemoglobin is 13.8 g/dL, peripheral smear is normal, and hemoglobin electrophoresis shows HbA 61%, HbS 39%. CT urography shows blunted calyces with small renal papillary calcifications bilaterally. What explains his hematuria?
- A Autosomal dominant polycystic kidney disease
- B Renal medullary sickling causing papillary necrosis despite normal peripheral blood ✓
- C IgA nephropathy triggered by sickle hemoglobin
- D Renal vein thrombosis
Correct answer: B. Renal medullary sickling causing papillary necrosis despite normal peripheral blood
Explanation
Even in sickle cell trait, the renal medulla provides the ideal milieu for sickling: low oxygen tension, high osmolality, and low pH concentrate HbS in the vasa recta. This causes papillary necrosis and painless hematuria, the commonest manifestation of sickle trait, though overall renal function remains normal. Polycystic kidney disease would show cysts, and renal vein thrombosis presents with flank pain and proteinuria rather than isolated papillary defects.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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