Calcium oxalate crystals

In ethylene glycol poisoning, oxalic acid binds to serum calcium to produce calcium oxalate crystals. These crystals precipitate in the tissues and cause end-organ toxicity (primarily of the kidney and brain), as well as potentially severe hypocalcaemia. Calcium oxalate crystals in the urine are indicative of ethylene glycol exposure; however, their absence does not exclude ethylene glycol ingestion.