Primary aldosteronism (PA) is mainly clinically classified as unilateral aldosterone-producing adenoma (APA) or bilateral idiopathic hyperaldosteronism. Immunohistochemistry for aldosterone synthase reveals a diverse PA pathology, including pathological APA and aldosterone-producing cell clusters. The relationship between PA pathology and adrenalectomy outcomes was examined herein. Data from 219 unilaterally adrenalectomized PA cases were analyzed. Pathological analyses revealed diverse putative aldosterone-producing lesions. Postoperative biochemical outcomes in 114 cases (test cohort) were classified as complete success (n = 85), partial success (n = 19), and absent success (n = 10). Outcomes in the large and small PA lesion groups, rather than between PA lesion types, were compared at five threshold values for PA lesion sizes (2–6 mm with 1-mm increments) to streamline the results. The proportion of complete success was significantly higher in the large PA lesion group than in the small PA lesion group at the 5-mm threshold only. The proportion of absent success was significantly higher in the small PA lesion group than in the large PA lesion group at all thresholds. Univariate and multivariate analyses of the test cohort identified serum K as an independent predictive factor for the small PA lesion group, which was confirmed in the 105-case validation cohort. Chi-squared automatic interaction detector analysis revealed that the best threshold of serum K for predicting large PA lesions was 2.82 mEq/L. These results will be beneficial for treating PA in clinical settings because patients with low serum K levels and apparent adrenal masses on CT may be subjected to adrenalectomy even if the adrenal venous sampling test is unavailable.
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