A 58-year-old woman with resistant hypertension (BP 165/95 mmHg despite amlodipine 10 mg and metoprolol 100 mg daily) undergoes screening for secondary hypertension. Plasma renin activity is markedly suppressed (0.3 ng/mL/hr; normal: 0.5–1.6), and serum aldosterone is elevated at 18 ng/dL (normal: 3–10 supine). Abdominal CT shows a 1.2 cm left adrenal nodule. What is the most appropriate next step in management?

Explanation

## Clinical Scenario: Primary Aldosteronism This patient presents with the classic triad of primary hyperaldosteronism (Conn syndrome): - Resistant hypertension - Suppressed plasma renin activity (low renin) - Elevated serum aldosterone (high aldosterone) - Adrenal nodule on imaging **Key Point:** The aldosterone-to-renin ratio (ARR) is diagnostic of primary aldosteronism, but imaging + biochemistry alone do NOT determine laterality. Adrenal venous sampling (AVS) is the gold standard for confirming unilateral disease before surgery. ## Why AVS Is Essential | Step | Purpose | Finding in This Case | |---|---|---| | **Biochemical confirmation** | ARR, suppression tests | Already done — ARR elevated | | **Imaging localization** | CT/MRI to detect nodule | 1.2 cm left nodule found | | **Functional lateralization** | AVS to confirm unilateral secretion | **NEXT STEP — not yet done** | | **Surgical decision** | Proceed to adrenalectomy only if AVS confirms unilateral source | Pending | **High-Yield:** A 1.2 cm nodule on CT is *not* diagnostic of aldosterone-secreting adenoma. Up to 10% of the population has incidental adrenal nodules. AVS measures aldosterone and cortisol from each adrenal vein to determine if aldosterone excess is truly unilateral; only then is adrenalectomy curative. ## AVS Interpretation ```mermaid flowchart TD A[Primary aldosteronism confirmed by ARR]:::outcome --> B[Adrenal imaging shows nodule]:::outcome B --> C[Perform AVS]:::action C --> D{Aldosterone gradient favors one side?}:::decision D -->|Yes, unilateral| E[Adrenalectomy on affected side]:::action D -->|No, bilateral| F[Medical management with MRA]:::action E --> G[Cure or significant BP improvement]:::outcome F --> H[Spironolactone or eplerenone long-term]:::action ``` **Clinical Pearl:** Bilateral adrenal hyperplasia accounts for ~60% of primary aldosteronism cases; unilateral adenoma accounts for ~35%. Without AVS, you risk operating on a patient with bilateral disease, which will not cure hypertension. AVS is the only way to reliably distinguish the two.