Primary aldosteronism: Update on diagnosis and treatment

Since its initial description in 1955, primary aldosteronism was thought to be a rare cause of hypertension. However, with improved screening methodologies, it appears that primary aldosteronism is the most common form of secondary hypertension. Patients with hypertension and hypokalemia and most patients with treatment-resistant hypertension should undergo screening for primary aldosteronism. A ratio of plasma aldosterone concentration (PAC; in ng/dL) to plasma renin activity (PRA; in ng/mL per hour) of >20 (with a PAC >15 ng/dL) is a positive screen for primary aldosteronism. An elevated PAC/PRA ratio is not diagnostic and primary aldosteronism must be confirmed by demonstrating inappropriate aldosterone secretion. The two major subtypes of primary aldosteronism are unilateral aldosterone-producing adenoma (APA) and bilateral idiopathic hyperaldosteronism (IHA). Patients with APA are usually treated with unilateral adrenalectomy, and patients with IHA are treated medically. The subtype evaluation may require one or more tests, of which the first is imaging the adrenals with computed tomography (CT). When a solitary unilateral macroadenoma (>1 cm) and normal contralateral adrenal morphology are found on CT in a patient with primary aldosteronism, unilateral laparoscopic adrenalectomy is a reasonable therapeutic option. However, in many cases, CT imaging may reveal normal-appearing adrenals or ambiguous findings. Adrenal venous sampling helps solve these clinical dilemmas.