What causes metabolic acidosis in ethylene glycol poisoning?

In ethylene glycol poisoning, metabolic acidosis is primarily caused by the production of calcium oxalate crystals. When ethylene glycol is ingested, it is metabolized in the liver to glycolic acid and oxalic acid among other metabolites. The oxalic acid can then combine with calcium in the body to form calcium oxalate crystals. The accumulation of these crystals can lead to renal damage and impaired kidney function, further exacerbating metabolic acidosis by hindering the body's ability to excrete acids.

Additionally, the glycolic acid produced during the metabolism of ethylene glycol contributes to the decrease in blood pH, leading to an acidotic state. The combination of increased acid load from the metabolic products and impaired renal function due to crystal formation results in significant metabolic acidosis seen in cases of ethylene glycol poisoning.