The role of laboratory testing in the diagnosis of renovascular hypertension.

The diagnosis of renovascular hypertension depends heavily on laboratory tests. There is no universally applicable screening test, and it should be actively sought only in patients with clinical clues suggested by the history, physical examination, and routine laboratory testing. Hyperreninemia is a characteristic finding, and acute blockade of the renin system forms the basis of diagnostic tests such as the oral captopril test and captopril renography. Other abnormal laboratory findings include hypokalemia, proteinuria, and azotemia exacerbated by angiotensin-converting enzyme inhibitors.