A 35-year-old woman with resistant hypertension (on 3 agents including a diuretic) has hypokalemia 2.9 mEq/L and an incidental 2.2 cm right adrenal nodule on CT. Plasma aldosterone-to-renin ratio (ARR) is markedly elevated at 45 (normal <30). This is consistent with primary aldosteronism. Which test is required before planning surgical versus medical management?

• A Saline infusion test to confirm aldosteronism
• B Adrenal vein sampling (AVS) to lateralize aldosterone excess ✓
• C Dexamethasone suppression test
• D Repeat CT with adrenal protocol in 6 months

Explanation

Once primary aldosteronism is confirmed biochemically (elevated ARR with confirmatory testing), adrenal vein sampling (AVS) is required to distinguish unilateral aldosterone-producing adenoma (APA, surgically curable by adrenalectomy) from bilateral adrenal hyperplasia (BAH, managed with mineralocorticoid receptor antagonists — spironolactone or eplerenone). CT cannot reliably lateralize in up to 40% of cases and may miss microadenomas or misidentify non-functioning contralateral nodules. AVS achieves >95% accuracy for lateralization when correctly performed. The saline infusion test confirms the diagnosis but doesn't lateralize.

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

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Written and medically reviewed by the StethoPrep medical team.