A 38-year-old man presents with hypertension (180/110 mmHg), hypokalemia (K+ 2.8 mEq/L), and metabolic alkalosis. Plasma aldosterone-to-renin ratio (ARR) is markedly elevated at 65 (ng/dL)/(ng/mL/h). CT adrenal shows a 1.4 cm left adrenal adenoma. What is the gold-standard next step to confirm lateralization before surgery?

• A Repeat CT with adrenal protocol
• B Saline infusion test
• C Start spironolactone and reassess
• D Adrenal vein sampling (AVS) ✓

Explanation

Adrenal vein sampling (AVS) is the gold standard for lateralization of aldosterone excess before adrenalectomy because CT alone misidentifies the source in up to 25–40% of cases—small adenomas may be missed or bilateral hyperplasia may be misidentified as a unilateral adenoma. The saline infusion test confirms primary hyperaldosteronism (suppression test) but does not lateralize. AVS demonstrates a lateralization index >4:1 confirming unilateral disease, guiding surgical resection.

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

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Written and medically reviewed by the StethoPrep medical team.