Calcium Oxalate Crystals in Ethylene Glycol Toxicity
An 80-year-old man with a remote history of alcohol-use disorder presented to the emergency department with altered mental status after a fall at home. He was somnolent and unable to provide any further history. Serum studies revealed a creatinine level of 2.4 mg per deciliter (212 μmol per liter; reference range, 0.6 to 1.3 mg per deciliter [53 to 115 μmol per liter]), a bicarbonate level of 9 mmol per liter (reference range, 21 to 32), an anion gap of 26 mmol per liter (reference range, 7 to 16), and a serum osmolality of 357 mOsm per kilogram of water (reference range 275 to 295), with an osmolal gap of 49 mOsm per kilogram of water (reference range, <10). Examination of urine sediment by means of light microscopy revealed calcium oxalate monohydrate crystals with two different morphologic features: narrow rectangles with pointed ends (Panel A, arrows) and dumbbell-shaped crystals (Panel B). Under polarized light, the crystals were positively birefringent; crystals were blue when parallel to the light and yellow when perpendicular to the light (Panel C). Given the high clinical probability of ethylene glycol toxicity, blood was drawn for measurement of the ethylene glycol level, and treatment with fomepizole and dialysis were initiated immediately. Ethylene glycol poisoning most commonly occurs after the ingestion of antifreeze or deicing solution. The patient’s ethylene glycol level, which became available 40 hours after the serum was drawn, was 211 mg per deciliter (34 mmol per liter; reference range, <1 mg per deciliter [<0.2 mmol per liter]). His mental status and renal function normalized after treatment with fomepizole for 3 days and four hemodialysis sessions over 5 days. The patient later reported that he had unintentionally ingested antifreeze.
Bu