An Unexpected Finding of Apparent Bilateral Aldosterone Suppression After Superselective Adrenal Venous Sampling: a case report

IntroductionIn adrenal venous sampling (AVS) for patients with primary aldosteronism (PA), apparent bilateral aldosterone suppression (ABAS) is occasionally experienced, but the underlying causes remain poorly understood.Case presentationA 40-year-old Chinese man with a right adrenal adenoma presented with hypertension and refractory hypokalemia. Initial AVS revealed no evidence of unilateral aldosterone excess and demonstrated ABAS. Six months later, repeat AVS was performed, during which two distinct venographic patterns-a "triangular pattern" and a "delta pattern"-were observed in the right adrenal vein depending on catheter position. Samples obtained from the main adrenal vein trunk suggested a right-sided source of aldosterone hypersecretion. The patient subsequently underwent right adrenalectomy and achieved both clinical and biochemical remission. Immunohistochemical staining for CYP11B2 confirmed an aldosterone-producing adenoma in the resected nodule.ConclusionThis case highlights a potential pitfall of superselective AVS and demonstrates that different venographic patterns of the right adrenal vein may result from varying catheter positions, which can critically influence diagnostic interpretation.