Which of the following are common causes of high anion gap metabolic acidosis in small animals?

• A. Lactic acidosis from sepsis/poor perfusion; Ketoacidosis; Uremic acidosis from renal failure or ethylene glycol poisoning
• B. Hypochloremic acidosis due to diarrhea
• C. Respiratory acidosis from hypoventilation
• D. Metabolic alkalosis due to diuretic use

Answer: (A)

High anion gap metabolic acidosis occurs when unmeasured anions build up in the blood, so the gap Na − (Cl + HCO3) widens. In small animals, this typically reflects accumulation of acids such as lactate, ketoacids, or toxin-derived acids.

The best answer captures the common causes: lactic acidosis from sepsis or poor tissue perfusion, ketoacidosis (e.g., diabetic or other ketoacidosis), and uremic acidosis from renal failure or toxins like ethylene glycol. These scenarios introduce extra anions (lactate, ketones, glycolate/oxalate) that lower bicarbonate and raise the anion gap.

The other options describe conditions that do not produce a high anion gap. Hypochloremic acidosis from diarrhea is a normal or non–anion-gap (hyperchloremic) metabolic acidosis due to bicarbonate loss with chloride gain. Respiratory acidosis from hypoventilation is a primary disturbance of CO2 and pH, not a metabolic acidosis with an increased anion gap. Metabolic alkalosis from diuretic use raises bicarbonate and pH, not a metabolic acidosis.