Primary aldosteronism:

B. Is suggested by findings of serum potassium less than 3.5 mEq. per liter, urinary potassium excretion greater than 30 mEq. per day, upright plasma renin below 3 ng. per ml., and a plasma aldosterone concentration–plasma renin activity ratio greater than 20:1.

C. Is most often due to an aldosterone-producing adrenal adenoma, which may be distinguished from idiopathic adrenal hyperplasia by its sensitivity to diurnal changes in ACTH and insensitivity to changes in posture.

DISCUSSION: Primary aldosteronism is a syndrome of diastolic hypertension and hypokalemia; edema typically is absent. The diagnosis relies on demonstration of hypokalemia with inappropriate kaliuresis and inappropriately elevated plasma aldosterone with suppression of plasma renin following sodium loading. Primary aldosteronism most often is due to an adrenal adenoma, which must be distinguished from idiopathic adrenal hyperplasia since resection of the adenoma is nearly always curative, whereas adrenal resection for idiopathic adrenal hyperplasia is curative less than 20% of the time. CT evidence of adrenal tumor alone is inadequate to diagnose aldosteronism, even in a hypertensive patient.