Preoperative Supine Time for Adrenal Venous Sampling

This study investigates whether the amount of time a patient lies flat (supine) before a procedure called adrenal venous sampling (AVS) affects the test results. AVS is used to figure out which adrenal gland is overproducing a hormone called aldosterone in people with primary aldosteronism (a condition causing high blood pressure). **You may be eligible if...** - You have been diagnosed with primary aldosteronism based on blood test results and confirmatory testing - You have agreed to undergo adrenal venous sampling (AVS) - You are 18 or older **You may NOT be eligible if...** - You are suspected of having adrenal cancer or a different adrenal tumor (pheochromocytoma) - You have a high-risk condition that makes adrenal surgery dangerous - You have already been identified as having a specific type of hereditary aldosteronism - You have Cushing's syndrome or are currently on steroid treatment Talk to your doctor to see if this trial is right for you.