A crystal clear diagnosis

Series Editor: Herbert L. Fred, MDPrepared by Dipen Parikh, MD, Resident, and Niraj Mehta, MD, Attending Physician, Department of Internal Medicine, Lyndon B. Johnson Hospital, Houston, TX

A 34-year-old man was brought to the hospital after his family found him unresponsive. Aside from an altered sensorium, his physical examination was normal. Laboratory studies showed severe metabolic acidosis and urinary crystals (Figure). Ethylene glycol was detected in a serum assay, and the patient was treated with fomepizole (Antizol) and hemodialysis. His condition rapidly improved. On follow-up 3 weeks later, he was asymptomatic, and he admitted to swallowing ethylene glycol in a suicide attempt.

Points to remember: Ethylene glycol is a colorless, odorless, sweet-tasting chemical predominantly found in automotive products such as antifreeze. A serum assay is the most definitive means of establishing this chemical's presence in humans. This assay, however, is not always readily available. In such cases, the diagnosis can be made when calcium oxalate monohydrate crystals are found in the urine. Often, calcium dehydrate urinary crystals are also present. Treatment involves limiting ethylene glycol metabolism by inhibiting alcohol dehydrogenase (accomplished by administering fomepizole) or by removing ethylene glycol from the serum (through hemodialysis).

Diagnosis: Ethylene glycol intoxication.

Figure—Microscopic examination showing calcium oxalate dehydrate crystals (A) and calcium oxalate monohydrate crystals (B) in urinary sediment.