Adrenal venous sampling in primary aldosteronism: success rate and CT correlation WM Yu (1), SS Lo (1), CS Chan (1), SM Yu (1), HC Lee (1)  (1)Department of Radiology, United Christian Hospital, Hong Kong SAR Adrenal venous sampling (AVS) is the gold-standard procedure in diagnosing the subtype of primary aldosteronism. Aldosterone-producing adenoma and unilateral adrenal hyperplasia are treated with adrenalectomy whereas bilateral adrenal hyperplasia is managed by mineralocorticoid antagonists. Both AVS and CT scan are performed in the workup of primary aldosteronism but each have their own limitations. AVS is a technically demanding mainly because the right adrenal vein is small and short making it difficult to cannulize and aspirate blood. CT scan may identify adrenal nodule but is unable to determine the functional status and confusion often arise when bilateral adrenals nodules are present. Objective: To review the success rate and safety of adrenal venous sampling (AVS) as well as its concordance with pathology and CT imaging in United Christian Hospital (UCH) Materials and Methods: From 2009-2017, all patients with primary aldosteronism who underwent AVS in UCH were included. Their pre-operative and post-operative blood pressures, antihypertensive drug usage, potassium levels, CT imaging, cortisol and aldosterone levels in adrenal and peripheral veins, complication and pathology findings are studied.   Results: 19 patients underwent 20 AVS from 2009-2017. One patient had repeat AVS due to failed first attempt. Using a cut off selectivity index of 3, the success rate for right adrenal vein cannulization is 65% (13/20) and 95% for left adrenal vein cannulization (19/20). No complication was reported.  AVS identified 11 patients with suspected unilateral aldosterone-producing adenomas and 3 patients with bilateral adrenal hyperplasia. CT results show 12 unilateral adrenal adenomas, 1 bilateral adrenal adenomas and 1 with normal adrenals. Concordance was seen in 11 (79%) out of 14 patients. All 11 patients who had suspected unilateral aldosterone-producing adenomas on AVS underwent adrenalectomy and confirmed cortical adenoma. They all showed contralateral adrenal suppression of aldosterone secretion using contralateral ratio <1. All had normalization of hypokalemia and improvement in hypertension except one with no improvement of blood pressure and one who did not have hypokalemia at baseline.  CT result AVS result Right Left Bilateral 4 1 6 No abnormality Concordance 4/4 (100%) for right; 6/7 (86%) for left; total 10/11(91%) 1/3 (33%) Among the 11 patients with unilateral aldosterone-producing adenomas, 10 had concordant CT findings and 1 had discordant findings on CT. Overall concordance is 91%. Among the 3 patients with bilateral adrenal hyperplasia, only 1 had concordant CT findings and 2 had discordant findings. The concordance rate is only 33%. Conclusion : Adrenal venous sampling is a safe procedure with relative high yield of success in experienced hands. As the concordance between CT imaging with AVS result is poor regarding bilateral adrenal hyperplasia, adrenal venous sampling is still indispensable in lateralization of primary aldosteronism.   References: CH Lam et al. Management of Primary Aldosteronism: Should Adrenal gland CT be replaced by adrenal venous sampling? HK J Radiol. 2014;17: 23-9 John W. Funder et al. The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, May 2016, 101(5):1889-1916