What are the steps involved in the adrenal vein sampling procedure?

Adrenal Vein Sampling Procedure Steps

Adrenal vein sampling (AVS) is performed to lateralize aldosterone production in primary aldosteronism by simultaneously or sequentially catheterizing both adrenal veins and measuring aldosterone and cortisol levels to distinguish unilateral adenomas (surgically curable) from bilateral hyperplasia (medically managed). 1

Pre-Procedure Preparation

Patient Selection and Timing

• AVS is indicated after confirming primary aldosteronism diagnosis through positive aldosterone-to-renin ratio (typically >30 when aldosterone is in ng/dL and renin activity in ng/mL/h, with aldosterone ≥10 ng/dL) and confirmatory testing (saline suppression or oral salt loading). 1
• Mineralocorticoid receptor antagonists (spironolactone, eplerenone) must be withdrawn for at least 4 weeks before testing. 1
• Ensure serum potassium is normalized and patient has unrestricted salt intake prior to the procedure. 1

Pre-Procedure Imaging

• CT imaging should be performed before AVS to demonstrate adrenal vein anatomy and positions, which aids in planning catheter approach and identifying anatomic variations. 2
• CT alone is unreliable for lateralization—25% of patients would receive inappropriate adrenalectomy based on CT findings alone, making AVS essential. 3

Technical Procedure Steps

Catheterization Technique

• The right adrenal vein is the most technically challenging to catheterize and represents the crux of successful AVS—it drains directly into the inferior vena cava at a sharp angle. 2, 4
• Simultaneous bilateral catheterization is preferred over sequential sampling to minimize timing-related differences in hormone levels between sides. 5
• Both adrenal veins are catheterized using fluoroscopic guidance, typically via femoral vein access. 2, 4

Contrast Injection and Confirmation

• A small amount of contrast material is injected gently and slowly into each adrenal vein—formal venography to outline the entire gland is not necessary. 2
• Gentle injection technique is critical to avoid adrenal vein rupture or spasm. 2, 5

Blood Sampling Protocol

• Blood samples are drawn from both adrenal veins and a peripheral vein for measurement of aldosterone and cortisol levels. 2, 4
• Cortisol measurement in the catheterization samples is used to confirm proper catheter placement—the adrenal vein sample should have significantly higher cortisol levels than the peripheral sample. 1, 2
• Many centers administer cosyntropin (ACTH stimulation) during the procedure to maximize cortisol gradients and improve confirmation of successful cannulation. 6

Interpretation Criteria

• Successful cannulation is confirmed when adrenal vein cortisol is significantly elevated compared to peripheral cortisol levels. 1, 2
• Adrenal glands producing aldosterone demonstrate an aldosterone-to-cortisol ratio that is higher than the peripheral value. 2
• Lateralization is determined by comparing the aldosterone-to-cortisol ratios between the two adrenal veins. 2, 4

Post-Procedure Management

Clinical Decision-Making

• If unilateral aldosterone production is documented, the patient is referred for unilateral laparoscopic adrenalectomy, which improves blood pressure in virtually 100% of patients and cures hypertension in approximately 50%. 1
• If bilateral aldosterone secretion is confirmed, or if the patient cannot undergo surgery, medical management with spironolactone or eplerenone is the treatment of choice. 1
• AVS results alter clinical management in 35.7% of primary aldosteronism patients who would have been treated improperly based on imaging alone. 4

Common Pitfalls and Technical Considerations

Technical Success Rates

• Technical success rates improve dramatically with operator experience—success rates of 58% in early years can increase to 95% with experience, and rates as high as 97% are reported in experienced hands. 4, 6
• The procedure should be performed by high-volume operators to maximize success rates. 6

Critical Caveats

• Never proceed with adrenalectomy based on CT imaging alone without AVS in surgical candidates—CT is unreliable for distinguishing unilateral from bilateral disease. 1, 3
• Some guidelines recommend AVS in all cases of primary aldosteronism, though it may be reasonable to exclude AVS in patients aged <40 years with clear unilateral adenoma on imaging. 1
• AVS is considered the gold standard and is mandatory before offering adrenalectomy to avoid unnecessary surgery in patients with bilateral hyperplasia. 1, 4
• Repeat AVS may be necessary if initial sampling is unsuccessful—secondary success rates of 95% are achievable with repeat procedures. 6