Endocrine Abstracts

Background: Subtyping of primary aldosteronism (PA) using imaging and adrenal vein sampling (AVS) can yield discordant results. Varying interpretation criteria in determining AVS lateralization may affect discordance rates.

Methods: We identified 337 consecutive patients with PA who underwent AVS at a quaternary care centre between August 2006 and February 2018. Patient demographics, laboratory results, diagnostic imaging, AVS results, and pathology were retrieved. Adrenal cross-sectional imaging was compared with AVS findings. Imaging was considered abnormal if any discrete nodule, bulkiness, or hyperplasia was reported. The presence of lateralization was defined using varying thresholds for the lateralization index (LI) from >4:1 to >2:1. Discordance was defined by a unilateral lesion on imaging with contralateral lateralization or bilateral disease on AVS.

Results: A total of 334 patients had adrenal imaging and 325 had technically successful AVS. The median age was 52 years, 58.8% were male, and hypokalemia was present in 67.5%. A total of 194 (58.1%) had unilateral lesions, 44 (13.2%) had bilateral lesions, and 96 (28.7%) had normal imaging. When present, unilateral lesions were more common on the left (67.0%) than the right (33.0%). Discordance between imaging and AVS was correlated with LI threshold stringency. Using the most ‘strict’ threshold of >4:1, the discordance rate was highest at 26.4%. Using ‘lenient’ thresholds of >3:1 and >2:1, the discordance rates were 23.7% and 22.0%, respectively. Lateralization, when present, was balanced between left and right irrespective of LI thresholds (44.0:56.0% for >4:1; 46.1:53.9% for >3:1, and 46.0:54.0% for >2:1).

Discussion: Discordance between imaging and AVS was common, and differences were greatest with ‘stricter’ AVS interpretation criteria. The preponderance of left-sided lesions seen on imaging, but not on AVS, is likely due to difficulties visualizing right-sided lesions on imaging rather than from biological differences.