RESUMEN
A 9 yr old cat was presented with clinical signs and laboratory abnormalities attributed to arterial hypertension (mean systolic arterial pressure, 290 mm Hg). Plasma aldosterone concentration was increased at the time of admission (651 pmol/L), but serum creatinine and potassium concentrations were within the reference range. A second increased aldosterone (879 pmol/L) and normal plasma renin activity (1.85 ng/mL/hr) resulted in an increased aldosterone/renin ratio, which was suggestive of primary hyperaldosteronism (PHA). To further support the diagnosis of PHA, the urinary aldosterone/creatinine ratio was calculated both before and after oral administration of fludrocortisone acetate (0.05 mg/kg q 12 hr for 4 consecutive days). The urinary aldosterone/creatinine ratio was 92.6 × 10(-9) before fludrocortisone administration and 155.8 × 10(-9) 4 days later. Absence of suppression was typical of PHA. The cat had a limited response to antihypertensive medication and died before treatment for PHA could be instituted. A necropsy was not permitted by the owner.