Identification of the Etiology of Primary Aldosteronism with Adrenal Vein Sampling in Patients with Equivocal Computed Tomography and Magnetic Resonance Findings: Results in 104 Consecutive Cases

The objectives of this study were to investigate the usefulness of adrenal vein sampling in identifying the etiology of primary aldosteronism (PA) in patients with equivocal CT and MR findings. Between 1990 and 1999, 104 referred hypertensive patients (45 women and 59 men, aged 49.6 ± 11.6 yr) were diagnosed to have PA with inconclusive computed tomography scan and magnetic resonance results, based on established criteria. Adrenal vein sampling (AVS) for measurement of plasma aldosterone (A) and cortisol (C) levels was performed in all. Selectivity of AVS was assessed by the ratio between C levels in each adrenal vein and in the infrarenal inferior vena cava plasma (Cside/CIVC). A receiver operator characteristics analysis was carried out to establish 1) the best AVS-derived index, 2) the degree of selectivity that could provide an accurate diagnosis, and 3) whether a correct diagnosis could be made from a unilaterally selective AVS. An aldosterone-producing adenoma (average diameter, 12.2 ± 0.08 mm) was eventually diagnosed in 41 patients (39.4%) and was excluded in the rest. Adrenal vein rupture leading to partial adrenal loss occurred in 1 patient (0.9% complication rate). By assuming a cut-off value of Cside/CIVC ≥ 1.1, AVS was selective in 85.7% and 94.1% of cases on the right and left sides, respectively, and bilaterally in 80.6% of cases. Of all AVS-derived indexes, the A/C of one over the A/C contralateral side[ (A/C)side/(A/C)contralateral side] furnished the best diagnostic accuracy. With a bilaterally selective AVS, a value of (A/C)side/(A/C)contralateral side≥ 2 provided a conclusive etiological diagnosis of PA in 79.7% of cases. At variance, no accurate diagnosis could be made from unilaterally selective AVS. AVS was feasible and safe in most PA patients with inconclusive computed tomography and magnetic resonance scans. When bilaterally selective (i.e. Cside/CIVC≥ 1.1) a ratio of (A/C)side/(A/C)control≥ 2 provided the best compromise of sensitivity and false positive rate for lateralization of the etiology of PA.