Review: Diagnosis and management of primary aldosteronism

Abstract

JRAAS 2001;2:156-69 Introduction Primary aldosteronism (PAL) is characterised by aldosterone production which is excessive to the body’s requirements and relatively autonomous of its normal chronic regulator, angiotensin II (Ang II). Inappropriate aldosterone production results in excessive reabsorption of sodium via the amiloride-sensitive epithelial sodium channels situated within the distal tubule and collecting duct of the kidney (leading to hypertension), and continues in the face of suppression of the reninangiotensin system (RAS). Urinary loss of potassium, which is exchanged for sodium at the distal nephron, may eventually result in hypokalaemia if severe and prolonged enough. Because measurements of plasma aldosterone and plasma renin activity (PRA) have become readily available, it is now feasible to measure their relationship in all hypertensive patients. The wide application of the aldosterone/PRA ratio (ARR) has permitted the diagnosis of PAL in the absence of hypokalaemia,and more commonly, in fact, than in the presence of hypokalaemia. This has led to a new understanding that PAL is not a rare cause of hypertension, to be suspected only when hypokalaemia is present, but is probably the commonest, identifiable, specifically treatable and potentially curable form of hypertension. With most recent studies reporting prevalence rates for PAL that are much higher than those previously described in medical textbooks and reviews on the subject, the diagnosis of PAL is likely to become an increasingly frequent event. The ability to correctly apply diagnostic techniques involved in the workup of PAL and to interpret their results therefore represent skills of increasing importance for physicians who treat hypertension. This review focuses on the rationale and methodology of these diagnostic techniques, and on current approaches to management of patients with PAL.