A 42-year-old woman presents with hypertension (BP 164/98), hypokalemia (K 2.8 mEq/L), and metabolic alkalosis. Aldosterone-to-renin ratio (ARR) is 38 (ng/dL)/(ng/mL/hr). CT adrenal shows a 1.8 cm left adrenal adenoma. What is the NEXT best investigation before deciding on surgical vs medical management?

• A 131-I NP-59 adrenal scintigraphy
• B Saline infusion test
• C Dexamethasone suppression test
• D Adrenal vein sampling (AVS) ✓

Explanation

An elevated ARR with confirmatory testing establishes primary hyperaldosteronism; however, CT alone cannot reliably distinguish unilateral aldosteronoma from bilateral hyperplasia because up to 30% of apparent CT adenomas represent bilateral disease on AVS, and occult contralateral microadenomas can be missed. AVS remains the gold-standard lateralisation test before committing to adrenalectomy. Saline infusion test is used for confirmation of primary aldosteronism, not lateralisation. NP-59 scintigraphy has lower resolution; dexamethasone is used for cortisol excess.

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

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Written and medically reviewed by the StethoPrep medical team.