Renovascular hypertension: nuclear medicine techniques.

Angiotensin converting enzyme inhibition (ACEI) renography is the only imaging examination that tests directly for the presence of renovascular hypertension (RVH); other imaging examinations test for the presence of renal artery stenosis (RAS). The goals of ACEI renography are two-fold: 1) to detect those patients with hypertension who have renal artery stenosis as the cause of their hypertension and who would benefit from revascularization, and 2) to determine which hypertensive patients do not have renovascular hypertension and obviate the expense and risk of angiography and, potentially, revascularization. This review summarizes general components of renal scintigraphy (pretest voiding, hydration, patient position, relative uptake, time to peak height of the renogram curve, 20 min/max ratio, postvoid images, quality control) as well as those components specific to ACEI renography (choice of radiopharmaceutical, choice of ACE inhibitor, angiotensin II receptor blockers, diuretics, parenchymal mean transit time, monitoring of blood pressure, 1 versus 2 day protocols and omission of the baseline study). ACEI renography is highly accurate in patients with suspected RVH who have normal or near normal renal function. In this patient population, the sensitivity and specificity of ACEI renography for renovascular hypertension exceed 90%; angiography as an initial approach is not cost effective. Data from 10 studies evaluating cure or improvement in blood pressure in 291 patients undergoing revascularization showed the mean positive predictive value of ACEI renography to be 92%. When azotemic patients present with suspected RVH, as many as 50% of patients may have an intermediate probability ACEI renogram and the sensitivity of detecting RVH falls to approximately 80% even when intermediate and high probability tests are combined.