Role of unilateral-cannulating adrenal venous sampling for the subtyping of primary aldosteronism for adrenalectomy: Experience from a low-volume center

Background: Current guidelines recommend adrenal venous sampling (AVS) for subtyping primary aldosteronism (PA). However, bilateral adrenal cannulation failure is common especially at low-volume centers. The role of unilateral-cannulating AVS in selecting patients for unilateral adrenalectomy is unclear.

Methods: Fifty consecutive patients underwent AVS between 2009 and 2023 and thirty-three (66%) underwent unilateral adrenalectomy. We defined unilateral PA (uPA) by the normalized plasma aldosterone and the aldosterone-renin ratio following unilateral adrenalectomy. We examined the effectiveness of unilateral-cannulating AVS in identifying uPA.

Results: 88%, 50%, and 48% of patients had the left, right, and bilateral adrenal veins successfully cannulated, respectively. Among patients with bilateral successful cannulation, a lateralization index (LI) > 4 provided a sensitivity of 100% and a positive predictive value (PPV) of 86.7% for uPA. Thresholds for the contralateral suppression index (CSI) and relative aldosterone secretion index (RASI) were derived from this subgroup and applied to the entire cohort. CSI <0.5 demonstrated a sensitivity of 76.5% and PPV of 92.9% for uPA, whereas RASI >2.4 showed a sensitivity of 85.0% and PPV of 94.4% for uPA. With CSI <0.5 or RASI >2.4 combined, a higher PPV (95.5%) was achieved when compared to computed tomography and iodocholesterol scintigraphy (86.2% and 62.5%, respectively).

Conclusion: Despite unsuccessful bilateral cannulation, our study confirms that unilateral-cannulating AVS can effectively select patients for unilateral adrenalectomy based on a combination of CSI or RASI criteria.