A 45-year-old woman with chronic daily use of analgesic combinations (phenacetin-containing) for tension headaches presents with sterile pyuria, microscopic haematuria, and gradually progressive CKD. CT scan without contrast shows bilateral shrunken kidneys with calcifications at the papillary tips. Which pathology is responsible?
- A Analgesic nephropathy with papillary necrosis ✓
- B Acute tubular necrosis
- C Chronic interstitial nephritis due to NSAIDs
- D Urothelial carcinoma secondary to phenacetin
Correct answer: A. Analgesic nephropathy with papillary necrosis
Explanation
Classic analgesic nephropathy from chronic phenacetin-containing analgesics causes renal papillary necrosis, bilateral small kidneys with papillary calcifications, and chronic interstitial nephritis. CT showing biconcave 'ring-shaped' calcifications in sloughed papillae is pathognomonic. Distractor D (urothelial carcinoma) is a recognized association but does not explain the bilateral small kidneys and sterile pyuria of progressive CKD. NSAID-induced chronic interstitial nephritis does not produce papillary calcifications.
Reference: Brenner and Rector's The Kidney, 11th ed.
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