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Acute Urate Nephropathy — SCE Rheumatology MCQ

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HardCrystal ArthropathyAcute Urate NephropathySCE Rheumatology

A 55-year-old man with established tophaceous gout and bulky diffuse large B-cell lymphoma receives his first cycle of cytoreductive chemotherapy after allopurinol prophylaxis. Thirty-six hours later, he becomes oliguric and his serum creatinine rises from 92 to 438 micromol/L. Serum urate is 1,120 micromol/L, phosphate 1.25 mmol/L and adjusted calcium 2.28 mmol/L. Urine pH is 5.0, and microscopy shows abundant pleomorphic rhomboid, barrel-shaped and rosette-forming birefringent crystals. Renal ultrasonography shows no hydronephrosis. Which renal pathological process is most likely?

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Correct answer: D — Acute uric acid nephropathy from intratubular crystal precipitation

This is acute uric acid nephropathy. Rapid purine release after cytoreductive chemotherapy has produced marked hyperuricaemia, while acidic urine favours precipitation of poorly soluble uric acid within distal tubules and collecting ducts. The characteristic pleomorphic rhomboid, barrel-shaped and rosette-forming crystals support this mechanism. Xanthine nephropathy can complicate allopurinol use during tumour lysis, but the very high urate concentration and crystal morphology favour uric acid. Normal phosphate and calcium make calcium phosphate deposition less likely. Chronic gouty nephropathy causes gradual tubulointerstitial disease rather than abrupt oliguric kidney injury. Bilateral ureteric calculi would usually produce upper-tract dilatation or other evidence of postrenal obstruction, which is absent here.

Reference: Electronic Medicines Compendium, Fasturtec Summary of Product Characteristics, sections 4.4 and 5.1, revised 2023. https://www.medicines.org.uk/emc/product/1316/smpc