A 42-year-old woman has hypertension requiring 3 antihypertensive drugs, episodic flushing, and hypokalemia (serum K 3.0 mEq/L) without diuretic use. Aldosterone-to-renin ratio (ARR) is 42 (ng/dL)/(ng/mL/hr). CT adrenal shows a 1.2 cm left adrenal nodule. What is the DEFINITIVE diagnostic step before deciding between adrenalectomy and medical therapy?

• A MRI adrenal glands for better characterization
• B Proceed directly to left laparoscopic adrenalectomy based on CT findings
• C Confirm with a saline infusion suppression test only
• D Adrenal vein sampling (AVS) to confirm unilateral vs bilateral aldosterone hypersecretion ✓

Explanation

Primary hyperaldosteronism (Conn syndrome) is confirmed biochemically by a positive ARR (>30) and confirmatory test (saline infusion, fludrocortisone suppression). However, CT adrenal alone cannot reliably distinguish unilateral adenoma from bilateral adrenal hyperplasia (CT is concordant with AVS in only 50–60% of cases, even when a nodule is visible). Adrenal vein sampling (AVS) is the gold standard for determining lateralization before deciding on adrenalectomy (unilateral) vs. aldosterone antagonist therapy (bilateral). Without AVS, adrenalectomy on the wrong side risks surgical failure in bilateral disease.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.