What is the mechanism of ethylene glycol toxic injury?

• A. Glycolic acid causes metabolic acidosis and calcium oxalate crystals.
• B. Glycolysis is inhibited.
• C. Protein denaturation by glycolic acid.
• D. Glycolic acid metabolite causing metabolic acidosis (3-4 hours) and calcium oxalate crystals leading to renal damage.

Answer: (D)

Ethylene glycol toxicity comes from its metabolites, not the parent compound itself. Alcohol dehydrogenase converts ethylene glycol first to glycolaldehyde, then to glycolic acid (glycolate), which is the principal toxic metabolite. Glycolic acid accumulates and drives a high–anion gap metabolic acidosis. At the same time, glycolic acid is metabolized further to oxalate, which combines with calcium to form calcium oxalate crystals that deposit in the renal tubules, causing renal injury. The combination of metabolic acidosis and calcium oxalate deposition explains the renal damage seen in these patients. This is why the mechanism is best described as a glycolic acid metabolite causing metabolic acidosis and calcium oxalate crystal–related renal injury.