EXPRESS: Renin-Angiotensin-Aldosterone System Profiling in a Cat with Primary Hyperaldosteronism

Case Summary: A 17-year-old female spayed domestic shorthair cat was presented for evaluation of systemic hypertension, hypokalemia, and cervical ventroflexion. Abdominal ultrasonography identified a right adrenal mass. Increased serum aldosterone concentration by radioimmunoassay (2786 pmol/L) supported primary hyperaldosteronism, but the cat was receiving amlodipine, a renin-angiotensin-aldosterone system (RAAS)-activating medication, which can increase serum aldosterone concentrations. Equilibrium analysis evaluation of the RAAS showed markedly elevated aldosterone (2137 pmol/L) without elevated angiotensin II. The ratios of aldosterone to angiotensin II and to plasma renin activity surrogate were markedly increased, supporting aldosterone secretion that was inappropriate relative to the other RAAS components. The cat underwent right adrenalectomy and histopathology which confirmed adrenal adenocarcinoma. Relevance and novel information: The congruence of comprehensive RAAS analysis with currently accepted testing used to support the diagnosis of aldosterone-secreting neoplasia in the cat of this report supports future research into the potential clinical utility of RAAS profiling to diagnose primary hyperaldosteronism in cats, even when receiving RAAS-modifying medications.