Discordance Between Imaging and Adrenal Vein Sampling in Primary Aldosteronism Irrespective of Interpretation Criteria

Davis Sam; Gregory A. Kline; Benny So; Alexander A. Leung

Disclosures

J Clin Endocrinol Metab. 2019;104(6):1900-1906. 

In This Article

Abstract and Introduction

Abstract

Background: Subtyping of primary aldosteronism (PA) using imaging and adrenal vein sampling (AVS) may yield discordant results, causing confusion in management. Interpretation criteria for AVS lateralization may affect discordance rates.

Methods: We identified consecutive patients with PA who underwent AVS at a quaternary care center between January 2006 and May 2018. Patient demographics, laboratory results, diagnostic imaging, and AVS results were retrieved. Adrenal cross-sectional imaging was compared with AVS findings. The presence of lateralization was defined using varying thresholds for the lateralization index (LI) from >2:1 to >5:1. Discordance was defined by a unilateral lesion on imaging with contralateral or nonlateralization on AVS.

Results: A total of 342 patients were included; 68.7% had hypokalemia. With cross-sectional imaging, 191 (55.6%) patients had unilateral lesions, 47 (13.7%) had bilateral lesions, and 104 (30.4%) had normal imaging. Overall discordance rates were high, ranging from 22% to 28% for LI thresholds of >2:1 and >5:1, respectively. Discordance between imaging and AVS was positively correlated with LI threshold stringency (P < 0.001). Patients with normal or bilateral lesions on imaging frequently lateralized on AVS. Lateralization, when present, was approximately equal between left and right sides, irrespective of the LI threshold.

Conclusions: Discrepancies between imaging and AVS were common, even among patients with nonspecific imaging. Discordance was greatest with the strictest AVS interpretation criteria. Even under the most lenient thresholds, apparent discordance between imaging and AVS exceeded 20% and may limit the ability to make surgical decisions. Reliance on imaging alone for detecting lateralization may be misleading.

Introduction

Primary aldosteronism (PA) is a potentially curable cause of hypertension and is present in up to 20% of individuals evaluated in hypertension clinics.[1] Accurate subtyping of PA informs the use of highly effective disease-targeted treatments. Unilateral PA may be amenable to surgery, whereas bilateral forms of disease are treated with mineralocorticoid receptor antagonists. Adrenalectomy in patients with unilateral disease leads to cure or improvement of hypertension in most cases,[2] improves quality of life,[3] and is cost-effective,[4] underscoring the importance of accurate subtyping.

Although adrenal vein sampling (AVS) is widely considered to be the definitive preoperative test for subtype diagnosis,[5–8] its use may be limited because of technical challenges and lack of availability. As such, adrenal cross-sectional imaging with CT or MRI is often recommended as the first step for subtype classification owing to its relative accessibility and ease of performance.[9,10] Moreover, despite the paucity of supporting evidence, some experts argue that AVS can be avoided in certain situations where a solitary adrenal nodule is seen on CT/MRI in association with biochemical features of aldosterone excess, with recommendations to proceed directly to adrenalectomy in selected cases.[7,9,11]

These recommendations are, in part, due to inconsistent reports comparing the performance of CT/MRI with AVS in identifying unilateral aldosterone hypersecretion. Even when a discrete unilateral lesion is detected on CT/MRI, aldosterone hypersecretion may arise from the contralateral side or bilaterally; furthermore, when apparent bilateral disease is seen on imaging, hypersecretion may be demonstrated to be unilateral with AVS. Previous studies examining the rates of discordance between subtyping modalities have been limited by nonstandardized imaging protocols and large differences in AVS interpretation criteria.[8] The potential impact of different interpretation criteria on rates of discordance has not been studied. We hypothesized that stricter thresholds for determining lateralization on AVS would result in greater rates of discordance. In other words, application of more stringent lateralization criteria (a condition that is more likely to capture true cases of unilateral aldosterone hypersecretion) would result in greater apparent discrepancies between cross-sectional imaging and AVS and predispose toward a higher likelihood of misclassification by imaging. To address this, we conducted a cohort study of all patients undergoing subtyping for PA through a centralized regional center with a standardized practice and protocol and compared the results of CT/MRI vs AVS.

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