Introduction
Subtype classification method is essential when considering adrenalectomy as a possible treatment for primary aldosteronism. We aimed to retrospectively evaluate surgical outcomes of primary aldosteronism in patients who had undergone ¹¹C-metomidate positron emission tomography (¹¹C-MTO-PET) for subtype classification.

Methods
Postoperative clinical and biochemical cure and histopathological diagnosis from biobank samples were retrospectively evaluated in 44 patients who had all undergone preoperative ¹¹C-MTO-PET with or without adrenal venous sampling (AVS). We compared those operated based on ¹¹C-MTO-PET alone and those with concordant or discordant lateralization in ¹¹C-MTO-PET and AVS studies according to postoperative immunohistochemical findings and biochemical and clinical cure.

Results
Adrenalectomy side was based on ¹¹C-MTO-PET alone in 14 cases and on AVS in 30 cases of whom 42 achieved complete and two partial biochemical cures. Among those who underwent AVS and were operated according to it, the two lateralization methods were concordant in 22 cases and discordant in 8 cases. Similar immunohistochemical profiles and cure rates were seen after ¹¹C-MTO-PET alone or AVS-based operations. Respectively, those with concordant or discordant ¹¹C-MTO-PET and AVS lateralization did not differ in surgical outcome. Together, we found errors of lateralization diagnostics with ¹¹C-MTO-PET in 18% and with AVS in 3% among those eligible for adrenal surgery.

Conclusions
Outcomes of adrenalectomy based on clinically significant lateralization in ¹¹C-MTO-PET alone correspond to those based on ¹¹C-MTO-PET with concordant AVS lateralization. However, our results suggest that diagnosis of unilateral PA should be performed with caution with ¹¹C-MTO-PET in case of discordant lateralization studies.