Ethylene glycol poisoning in cats: crystals and anion gap
3-year-old cat with outdoor access presenting with acute vomiting, ataxia and depression. The sediment contains abundant elongated "picket fence" or prism-shaped crystals.
| Parameter | Result | Reference |
|---|---|---|
| Creatinine | 4.8 mg/dL | 0.8–2.4 |
| Bicarbonate | 9 mmol/L | 17–24 |
| Anion gap | 38 mmol/L | 13–27 |
| Glucose | 150 mg/dL | 70–150 |
| Crystals | Abundant calcium oxalate monohydrate | — |
What is the most likely diagnosis?
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A. Calcium oxalate urolithiasis with obstruction
Oxalate uroliths are more often accompanied by dihydrate crystals and do not explain ataxia or such a high anion gap acidosis in a cat without signs of obstruction.
B. Acute kidney injury from lily ingestion
Lilies cause severe AKI in cats, but do not produce oxalate crystalluria or early ataxia. The combination of crystals and a very high anion gap points to ethylene glycol.
C. Diabetic ketoacidosis
It also causes high anion gap acidosis, but requires marked hyperglycaemia and ketonuria. A glucose of 150 mg/dL in a stressed cat does not support it.
D. Ethylene glycol (antifreeze) poisoning
Correct. The acid metabolites of ethylene glycol cause metabolic acidosis with a very high anion gap, and oxalate precipitates in the tubules and urine as monohydrate crystals, causing acute kidney injury. The early neurological signs fit.
lightbulb Key takeaway
In cats the window is very short: the antidote (fomepizole at feline doses or ethanol) is only effective in the first few hours, before azotaemia. With acute ataxia in an outdoor cat, think antifreeze and check the sediment and anion gap.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.