MON-301 Laterlising PA in Young Patients: Can Imaging Alone Be Trusted?

Abstract Disclosure: Z. Htut: None. N. Asmar: None. J. Agilinko: None. A. Alsafi: None. F. Wernig: None. Background: The role of adrenal vein sampling (AVS) in younger patients with primary aldosteronism (PA) remains debated. The Endocrine Society (ES) Guidelines suggest that AVS may be omitted in patients ≤35 years with marked PA (aldosterone >831 pmol/L, spontaneous hypokalaemia), and a solitary adrenal lesion consistent with an adenoma. While some centres follow this approach, others, including ours, perform AVS in all PA patients. However, relying solely on imaging may misclassify laterality in a substantial proportion of younger patients, potentially leading to inappropriate management decisions. Aim: To determine the accuracy of imaging alone in differentiating unilateral from bilateral PA in patients ≤35 years and assess the added diagnostic value of AVS. Method: We retrospectively analysed 364 PA patients who underwent AVS between 2011 to 2024, including 39 patients aged ≤35 years. Of these, 38 had pre-AVS imaging (CT/MRI). Two radiologists independently assessed imaging, blinded to AVS results, while two endocrinologists blinded to imaging, analysed AVS. Concordance between imaging and AVS was evaluated. Results: The mean age was 32 years, with 60% female. Median hypertension duration was 1.5 years (IQR: 1-5 years). All had biochemically confirmed PA with spontaneous hypokalaemia and required two to three antihypertensive medications. AVS was technically successful in all cases. Four patients were excluded due to inconclusive AVS results and missing imaging data.Among the remaining 35, imaging suggested unilateral adenomas (6-25 mm) in 82.9% (29/35), bilateral adenomas in 8.6% (3/35), and normal adrenal glands in 8.6% (3/35). However, AVS revealed discordant findings in 13.8% (4/29) of those with unilateral adenomas, indicating bilateral disease. Discordant cases had lateralisation index <2 (range: 1.3-2.0) and/or contralateral suppression index >1, suggesting bilateral PA. Only one discordant case met ES criteria for marked PA, while the remaining three had milder disease. All discordant cases were managed medically, whereas 86.2% (25/29) underwent unilateral adrenalectomy, with histologically confirmed adenoma. Conclusion: Although imaging correctly lateralised PA in 86.2% of cases, 13.8% of patients with apparent unilateral adenomas on imaging had discordant AVS findings, confirming bilateral disease. Notably, only one discordant case met the ES criteria for marked PA, supporting AVS omission in this subset. However, for patients with milder PA, AVS remains critical to prevent misclassification and unnecessary adrenalectomy, reinforcing its continued role in refining treatment decisions. Presentation: Monday, July 14, 2025