The captopril test is a screening test to identify patients with renovascular hypertension versus those with essential hypertension. It exploits the hyper-responsive renin secretion in patients with renovascular hypertension. Captopril is an angiotensive converting enzyme (ACE) inhibitor; its administration results in an exaggerated increase in plasma renin levels in renovascular hypertension. Positive tests may be used to justify invasive procedures such as digital subtraction renal arteriography or renal vein renin level measurements.
