Diagnostic Challenges with Acyclovir Crystalluria - A Case Study

Marked to abundant crystalluria may cause significant morbidity due to acute renal injury. Intravenous acyclovir administration may result in a pathologic crystalluria, especially in cases with increased renal concentration of the drug. It is important that clinical laboratory staff recognize and communicate the presence of abundant crystalluria to clinical staff to avoid irreversible kidney injury.

We report a case of crystalluria in a patient treated empirically with intravenous acyclovir for possible viral meningitis.

Opaque "milky" urine was submitted for urine analysis which showed abundant long needle-shaped brightly birefringent crystals under polarized light microscopy and was diagnosed as acyclovir crystalluria.

Any case of moderate to abundant crystalluria should be reported in a timely manner to the clinical staff to facilitate treatment modification to reduce the risk of acute kidney injury. Laboratory staff should be aware and recognize acyclovir treatment as a possible cause of pathologic crystalluria.