Adrenal Vein Sampling Indication in Primary Aldosteronism
Adrenal vein sampling (AVS) is mandatory before offering adrenalectomy to all patients with biochemically confirmed primary aldosteronism who are surgical candidates, as CT imaging alone leads to unnecessary adrenalectomy in up to 25% of patients. 1, 2
When AVS is Required
AVS must be performed after completing the following diagnostic sequence 2, 3:
- Positive screening test: Aldosterone-to-renin ratio (ARR) ≥30 with plasma aldosterone ≥10 ng/dL 2
- Confirmatory testing: Demonstration of autonomous aldosterone secretion that cannot be suppressed with sodium loading (via intravenous saline suppression test or oral sodium loading with 24-hour urine aldosterone) 2, 3
- Surgical candidacy: Patient agrees that surgery would be desirable if unilateral disease is identified 3
The Single Exception to AVS
AVS can be omitted only in patients <40 years of age when imaging shows a single unilateral adenoma, as bilateral hyperplasia is rare in this young population 2. In all other patients, AVS is mandatory regardless of CT findings 1, 2.
Why CT Imaging Alone is Insufficient
CT findings are unreliable for treatment decisions because 2:
- Adenomas on imaging can represent bilateral hyperplasia rather than unilateral disease
- False positives are common due to nodular hyperplasia
- Up to 25% of patients would undergo unnecessary adrenalectomy based on CT alone 1, 2
Critical Distinction: Unilateral vs Bilateral Disease
AVS serves as the gold standard (95% sensitivity, 100% specificity) for distinguishing unilateral from bilateral aldosterone hypersecretion, which determines treatment 2, 3:
- Unilateral disease: Laparoscopic adrenalectomy improves blood pressure in virtually 100% of patients and completely cures hypertension in approximately 50% 3
- Bilateral disease: Requires lifelong medical management with mineralocorticoid receptor antagonists (spironolactone or eplerenone) 3
Technical Considerations for AVS Success
The procedure involves catheterization of both adrenal veins with blood sampling to measure aldosterone and cortisol levels 3. Success rates and interpretation criteria significantly impact diagnostic accuracy:
- Selectivity criteria: Using a cortisol ratio (adrenal vein/peripheral vein) ≥5 achieves better reproducibility than permissive criteria 4, 5
- Lateralization index: LI ≥4 after ACTH stimulation indicates unilateral disease 6, 7
- Contralateral suppression: Absence of contralateral aldosterone suppression predicts lower surgical cure rates (13% vs 55% clinical cure when suppression is absent) 6, 7
Common Pitfalls to Avoid
- Never proceed to surgery based on CT findings alone without AVS confirmation, as this leads to inappropriate adrenalectomy in 25% of cases 1, 2
- Do not use permissive selectivity criteria (cortisol ratio <2.75), as these achieve poor diagnostic reproducibility with concordance in only 35.3% of repeat procedures 4
- Ensure ACTH stimulation during AVS, as this improves selectivity from 66.7% to 91.8%, though it can modify lateralization interpretation in 28% of cases 6
Multidisciplinary Review Requirement
A multidisciplinary review by endocrinologists, surgeons, and radiologists is recommended when 1:
- Imaging is not consistent with a benign lesion
- Evidence of hormone hypersecretion exists
- Adrenal surgery is being considered