What is adrenal vein sampling?

What is Adrenal Vein Sampling

Adrenal vein sampling (AVS) is an invasive catheterization procedure that directly measures aldosterone and cortisol levels from each adrenal vein to determine whether aldosterone overproduction in primary aldosteronism originates from one adrenal gland (unilateral, surgically curable) or both glands (bilateral, requiring medical management). 1

Purpose and Clinical Context

AVS is considered the gold standard for distinguishing unilateral aldosterone-producing adenomas from bilateral adrenal hyperplasia in patients with confirmed primary aldosteronism. 1, 2 This distinction is critical because:

• Unilateral disease is potentially curable with laparoscopic adrenalectomy, which improves blood pressure in virtually 100% of patients and completely cures hypertension in approximately 50%. 1
• Bilateral disease requires lifelong medical management with mineralocorticoid receptor antagonists (spironolactone or eplerenone). 1

The procedure is essential because CT imaging alone is unreliable—up to 25% of patients would undergo unnecessary adrenalectomy based on CT findings alone, as adenomas on imaging can represent hyperplasia and nodular hyperplasia causes frequent false positives. 1, 3, 4

When AVS is Indicated

AVS should be performed in the following clinical scenarios:

• After biochemical confirmation of primary aldosteronism (positive aldosterone-to-renin ratio ≥30 with plasma aldosterone ≥10 ng/dL, followed by positive confirmatory testing with saline suppression or oral salt loading). 1, 3
• In surgical candidates where the patient agrees that surgery would be desirable if unilateral disease is identified. 1
• Mandatory before offering adrenalectomy to prevent inappropriate surgical intervention. 1, 3

One important exception: AVS may be omitted in patients younger than 40 years with a clear unilateral adenoma on CT imaging, as bilateral hyperplasia is rare in this age group and unilateral lesions have greater positive predictive value (85%). 1, 4

Technical Procedure

The procedure involves:

• Catheterization of both adrenal veins (right and left) via a femoral or jugular venous approach. 2, 5
• Blood sampling from each adrenal vein and a peripheral vein to measure aldosterone and cortisol levels. 1, 5
• Cortisol measurement serves as a marker to confirm proper catheter placement in the adrenal vein (adrenal vein cortisol should be significantly higher than peripheral cortisol). 1, 5
• The right adrenal vein is technically challenging to cannulate due to its small size and direct drainage into the inferior vena cava, but technical success rates reach 97% in experienced hands. 2, 5

Interpretation of Results

• Selectivity is confirmed when the adrenal vein cortisol level is significantly higher than peripheral cortisol, proving the catheter is draining adrenal cortical blood. 5
• Lateralization is determined by comparing cortisol-corrected aldosterone ratios between the two adrenal veins. 1, 4
• A lateralization ratio >2 (affected side versus unaffected side) is 100% sensitive for identifying surgically curable unilateral adenomas. 4
• The relative aldosterone secretion index (RASI) can identify unilateral disease even with only unilaterally selective sampling, with RASI >2.55 on one side or ≤0.96 on the contralateral side providing high diagnostic accuracy. 6

Clinical Impact

AVS alters clinical management in 35.7% of primary aldosteronism patients who would have been treated improperly based on CT or other imaging alone. 2 The procedure is safe and highly effective when performed by experienced interventional radiologists. 2, 7