Adrenal Venous Sampling

Adrenal venous sampling is almost exclusively used in the setting of excessive aldosterone production to establish and localize unilateral aldosteronism before surgery. Excessive excretion of aldosterone may be primary due to a tumor (Conn syndrome) or hyperactivity of the outer area of the adrenal cortex, or secondary due to nonadrenal conditions that cause a severe imbalance in sodium and potassium. Examples of secondary causes of hyperaldosteronism are congestive heart failure, cirrhosis with ascites, depletion of sodium from diuretics, or toxemia of pregnancy. Plasma renin activity is typically elevated in secondary hyperaldosteronism and reduced in primary aldosteronism. As a result, aldosterone and renin are usually measured together.

Primary aldosteronism is increasingly considered to be a remedial cause of hypertension. Patients with an increased peripheral aldosterone:renin ratio after correction for hypokalemia and removal of interfering medication who also show a positive response to corticosteroid suppression should be considered for adrenal vein sampling to distinguish unilateral from bilateral primary aldosteronism. A multidisciplinary approach to management of these patients is essential for good clinical outcomes. In most cases, a computed tomography (CT) scan of the adrenal glands will have been performed to exclude obvious causes such as adrenal carcinoma. This should be evaluated in detail for adrenal venous anatomy. If there is evidence of a unilateral enlargement of a portion of the adrenal gland, there is slightly more likelihood of unilateral aldosteronism excess. In about 40% of cases of aldosteronism, however, the CT is unhelpful or even misleading.