A 45-year-old hypertensive man has an incidentally discovered 2.8 cm left adrenal mass. Plasma aldosterone-to-renin ratio (ARR) is 38 (normal <30), 24-hour urinary cortisol is normal, plasma metanephrines are normal, and CT shows a homogeneous lipid-rich nodule. The next best diagnostic step is:
- A Proceed directly to laparoscopic left adrenalectomy
- B Low-dose dexamethasone suppression test
- C Adrenal vein sampling (AVS) to lateralise aldosterone excess ✓
- D 131I-MIBG scintigraphy
Correct answer: C. Adrenal vein sampling (AVS) to lateralise aldosterone excess
Explanation
A raised ARR >30 with biochemical confirmation of primary aldosteronism requires adrenal vein sampling (AVS) to distinguish unilateral adenoma (amenable to surgery) from bilateral hyperplasia (managed with mineralocorticoid antagonists). CT alone is insufficient for lateralisation as it misclassifies ~25% of cases. MIBG is for phaeochromocytoma, and the dexamethasone test is for Cushing's syndrome, both of which have been excluded.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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