Adrenal venous sampling is crucial before an adrenalectomy whatever the adrenal-nodule size on computed tomography.

Objective: To assess the additional value of adrenal venous sampling (AVS) to diagnose primary aldosteronism sub-types in patients who have a unilateral nodule detected by computed tomography (CT scan) and who should undergo an adrenalectomy.

Methods: A retrospective study to assess consecutive patients with primary aldosteronism undergoing an adrenal CT scan and AVS. Criterion for selective cannulation was an equal or higher cortisol level in the adrenal vein compared to the inferior vena cava. An adrenal-vein aldosterone-to-cortisol ratio of at least two times higher than the other side defined lateralization of aldosterone production.

Results: Sixty-seven patients (mean age 52 years, 39 men) underwent a CT scan and AVS. In nine patients (13%), cannulation of the right adrenal vein led to a technical failure. Both procedures led to diagnosis of 29 patients with adenoma-producing aldosterone (APA; 50%), 23 bilateral adrenal hyperplasias (40%), and six unilateral adrenal hyperplasias (10%). Of the 45 patients with a nodule detected by CT, subsequent AVS showed bilateral secretion in 16 patients (36%). Compared to the strategy of coupling CT scans with AVS to diagnosis APA, a CT scan alone had an accuracy of 72.4% (P < 0.001). Among patients with a macronodule detected by CT, 13 (37%) had bilateral secretion as assessed by AVS. The patients with a macronodule detected by CT alone had the same risk of a discrepancy as those with a small nodule (P = 0.99).

Conclusion: AVS is essential to diagnose the unilateral hypersecretion of aldosterone, even in patients in whom a unilateral macronodule is detected by CT, to avoid unnecessary surgery.