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Ciprofloxacin Crystal Nephropathy — ESENeph MCQ

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HardAcute Kidney InjuryCiprofloxacin Crystal NephropathyESENeph

A 45-year-old man develops AKI after starting Ciprofloxacin for a UTI. His creatinine rises from 90 to 180 umol/L. Urine microscopy shows birefringent needle-shaped crystals under polarised light. Urine pH is 7.5 (alkaline). What is the mechanism?

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Correct answer: A — Intratubular Ciprofloxacin crystal deposition in alkaline urine

Fluoroquinolones (especially Ciprofloxacin) can crystallise in alkaline urine (pH >7), depositing in renal tubules and causing obstructive crystal nephropathy. Risk factors include alkaline urine, dehydration, and high-dose therapy. Needle-shaped birefringent crystals on urine microscopy are characteristic. Management involves stopping Ciprofloxacin, IV hydration, and acidifying urine if possible. This is distinct from fluoroquinolone-associated AIN, which involves immune-mediated inflammation without crystals.

Reference: Perazella 2019 – Drug-Induced Crystal Nephropathy; KDIGO 2012 – AKI