In patients with primary hyperaldosteronism, measurements of aldosterone and cortisol from the adrenal veins compared with levels in the inferior vena cava can help answer both the question of whether the patient has an adenoma or bilateral hyperplasia and on which side an adenoma is if one is present. Surgical resection of an adenoma will usually correct a patient's hypokalemia and hypertension, which is not the case if adrenal hyperplasia is present.