Abstract
Adrenal venous sampling （AVS） is essential for diagnosing subtypes of primary aldosteronism （PA）; however, its interpretation can be compromised by anatomical and physiological factors. This study aims to clarify how venous dilution and drainage variability obscure lateralization in technically successful AVS procedures. We analyzed five patients with AVS-confirmed unilateral PA who exhibited discordant radiological and hormonal findings. All patients underwent superselective AVS and a detailed imaging review. Anatomical variations and hormone gradients were examined to identify the root causes of these discordances. Three patients demonstrated the collecting dilution effect （CDE）, wherein tumor drainage merged with non-tumor-related venous flow. Nonrepresentative hormonal adrenal central veins （NRH-ACVs） were suspected in cases where the sampled central veins did not align with the functional laterality confirmed by superselective sampling and surgical outcomes. Even when catheterization is technically successful, lateralization may fail due to venous dilution or atypical drainage patterns. Recognizing these anatomical pitfalls can significantly improve diagnostic accuracy. An integrative analysis that combines venous anatomy with hormone gradients enhances clinical confidence in surgical planning.
