Type-II renal tubular acidosis and ventricular tachycardia in a horse.

A 14-year-old Arabian mare was admitted for lethargy, anorexia, and low fecal output. On the basis of laboratory, physical examination, and electrocardiographic findings, diagnoses of type-II renal tubular acidosis (RTA), impaction of the large colon, and ventricular tachycardia were made. Diagnosis of type-II RTA was based on measurement of a low fractional excretion value for potassium and fractional excretion value for sodium within the reference range. In contrast, horses with type-I RTA have high fractional excretion values for sodium and fractional excretion values for potassium within reference ranges. Treatment consisted of intravenous and oral administration of sodium bicarbonate, intravenous administration of fluids, and oral administration of mineral oil and docusate sodium. Acidosis improved, and ventricular tachycardia resolved with resolution of acidosis. Oral administration of bicarbonate was continued after discharge. The mare had several relapses, which were associated with anorexia and low intake of supplemental bicarbonate. The mare was found dead 2 months after discharge.