What is adrenal vein sampling (AVS), and when is it indicated?
AVS is an interventional radiology procedure in which endovascular catheters are used to selectively cannulate and sample blood from the right and left adrenal veins. There are technical limitations to accurate sampling, and the technique may not be universally available. APAs are typically < 2 cm in diameter, and therefore the sensitivity of CT is only 85%. AVS should be used in most patients with biochemically confirmed PA to exclude bilateral hyperplasia and confirm the correct side in those with an APA, which may be in the “normal” gland in the setting of an incidentaloma. Imaging results can be misleading in up to 20% of patients (bilateral adrenal masses but unilateral APA; unilateral adrenal nodule but small APA detected in contralateral “normal” gland). AVS may be omitted in younger patients (age < 35 years), as they are less likely to have confounding adrenal nodules.