Aciclovir Crystal Nephropathy Mechanism — ESENeph MCQ

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EasyAcute Kidney InjuryAciclovir Crystal Nephropathy MechanismESENeph

A 45-year-old woman develops AKI 10 days after starting high-dose intravenous aciclovir for herpes simplex encephalitis. Creatinine rises from 70 to 350 umol/L. Urine microscopy shows birefringent needle-shaped crystals. What is the mechanism of AKI?

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Correct answer: A — Intratubular crystal deposition and obstruction

Aciclovir is poorly soluble in urine and can precipitate as needle-shaped birefringent crystals within the renal tubules and collecting ducts, causing intratubular obstruction and direct tubular injury (crystal nephropathy). Risk factors include high-dose IV administration, rapid infusion, volume depletion, and pre-existing CKD. The crystals are birefringent under polarised light on urine microscopy. Prevention involves adequate hydration (to maintain urine output >100 mL/hr during infusion) and slow infusion rate. Treatment involves stopping aciclovir, aggressive IV hydration, and haemodialysis for severe cases. AKI is usually reversible if recognised promptly. Similar crystal nephropathy occurs with sulphonamides, methotrexate, and indinavir.

Reference: Perazella 2010 – Crystal-Induced AKI; JRCPTB 2022 – Nephrology Curriculum