The differentiation between subtypes of primary aldosteronism (PA) is fundamental to refer each patient to the most appropriate therapeutic approach (surgical in case of unilateral disease and medical in case of bilateral disease). Adrenal vein sampling (AVS) is currently considered the gold standard for such differentiation between subtypes.~However, despite significant progress in optimizing the AVS procedure, the percentage of unsuitable procedures due to the unsuccessful cannulation of one of the two adrenal veins is still considerable, especially in less experienced centers.~It would therefore be important to identify criteria for the interpretation of the results of a suboptimal AVS study (i.e. with sampling of only one of the two adrenal veins). This problem has recently been addressed by some groups; however, there is still no general consensus on these criteria and all existing studies must be considered exploratory in this field.~In this study, therefore, all patients with PA followed by our center and who underwent a successful (i.e. with correct cannulation and sampling from both adrenal veins) unstimulated (i.e. without cosyntropin stimulation) AVS procedure will be retrospectively evaluated.~If a reliable unilateral index could be identified for subtype diagnosis, this tool could be used for the interpretation of suboptimal AVS data, thus preventing a certain percentage of patients from the necessity to repeat the procedure and allowing to refer each one, also on the basis of an incomplete dataset, to the most appropriate therapeutic approach.
Adrenal vein sampling (AVS) is currently considered the gold standard for subtype diagnosis of primary aldosteronism (PA). However, the percentage of unsuitable procedures due to the unsuccessful cannulation of one of the two adrenal veins is still considerable, and there is no general consensus on the criteria that should be used for the interpretation of the results of an AVS study in these specific cases.