When to Perform Adrenal Venous Sampling (AVS)
Adrenal venous sampling should be performed in all patients with biochemically confirmed primary aldosteronism who are surgical candidates and would agree to adrenalectomy if unilateral disease is identified. 1, 2
Prerequisites Before AVS
AVS is indicated only after completing the following diagnostic steps:
Positive screening test: Aldosterone-to-renin ratio (ARR) ≥30 with plasma aldosterone concentration ≥10 ng/dL 1, 2, 3
Confirmatory testing completed: Either intravenous saline suppression test or oral salt-loading test demonstrating autonomous aldosterone secretion that cannot be suppressed 1, 2, 3
Patient preparation requirements met: Unrestricted salt intake, normal serum potassium levels, and mineralocorticoid receptor antagonists withdrawn for at least 4 weeks 1, 2, 3
Mandatory Indications for AVS
AVS is mandatory before offering adrenalectomy because CT imaging alone is insufficient and leads to significant management errors 1, 2, 4:
Up to 25% of patients would undergo unnecessary or inappropriate adrenalectomy based on CT findings alone 2, 4
21.7% of patients would be incorrectly excluded as surgical candidates if relying only on CT 4
CT cannot reliably distinguish unilateral aldosterone-producing adenomas from bilateral adrenal hyperplasia, which require completely different treatments 2, 5
Clinical Scenarios Requiring AVS
Perform AVS in patients with confirmed primary aldosteronism who have any of the following CT findings:
Normal-appearing adrenal glands: 41.4% of these patients have unilateral aldosterone hypersecretion amenable to surgical cure 4, 6
Unilateral micronodule (≤10 mm): 51.1% have unilateral disease, but 15% have hypersecretion from the contralateral adrenal 4
Unilateral macronodule (>10 mm): 65.6% have unilateral disease, though some have contralateral hypersecretion 4
Bilateral adrenal nodules: 48.5% still have unilateral aldosterone hypersecretion 4, 6
Atypical-appearing adenomas: AVS is crucial to confirm the functional source 6
Exception to AVS Requirement
The only exception is patients <40 years old with a single unilateral adenoma on imaging, as bilateral hyperplasia is rare in this population 2. However, even in this scenario, AVS provides the most definitive diagnosis.
Why AVS is Critical
The distinction between unilateral and bilateral disease determines treatment:
Unilateral disease (aldosterone-producing adenoma): Laparoscopic adrenalectomy improves blood pressure in virtually 100% of patients and completely cures hypertension in approximately 50% 1, 2
Bilateral disease (bilateral adrenal hyperplasia): Requires lifelong medical management with mineralocorticoid receptor antagonists (spironolactone or eplerenone) 1, 2
Common Pitfalls to Avoid
Do not proceed to surgery based on CT findings alone: Adenomas on imaging can represent non-functional nodules while the contralateral gland is the source of aldosterone excess 2, 4
Do not assume normal-appearing adrenals exclude surgical candidacy: 40% of patients with normal or minimally thickened adrenal glands on CT have unilateral disease 4, 6
Do not skip AVS in patients with bilateral nodules: Nearly half still have unilateral hypersecretion and are surgical candidates 4
Technical Considerations
AVS involves catheterization of both adrenal veins (right and left) with blood sampling from each adrenal vein and a peripheral vein to measure aldosterone and cortisol levels 2. Cortisol measurement confirms proper catheter placement, and lateralization is determined by comparing cortisol-corrected aldosterone ratios between the two adrenal veins 2. Both adrenal veins can be successfully catheterized in approximately 95% of cases 4, 5.