Noninvasive measurement of renal blood flow with technetium-99m-DTPA in the evaluation of patients with suspected renovascular hypertension If a hypertensive patient with renal artery stenosis (RAS) is to benefit from percutaneous transluminal renal angioplasty (PTRA) in terms of a sustained improvement in blood pressure control, one may postulate a demonstrable reduction in renal blood flow (RBF) to that kidney, reversible by PTRA. In a population of 32 hypertensive patients, RAS was present in 23 of 62 kidneys. Eleven of the 32 patients underwent renal revascularization, of whom 6 showed improvement in blood pressure control at 6 mo, i.e., had renovascular hypertension (RVH). There was no correlation between RBF and angiographic appearances of the renal artery. Furthermore, there was no significant difference between RBF in the stenosed kidneys of the patients with RVH compared with the stenosed kidneys of patients without RVH. Individual kidney RBF was 22% (s.d. 11) higher 1-3 wk after PTRA but the increase did not correlate with clinical outcome. Angiotensin converting enzyme (ACE) inhibition increased RBF by 25% (s.d. 25) of baseline flow before PTRA but the increase did not correlate with clinical outcome. Measurement of RBF is of limited value for the prediction of the long-term blood pressure response following PTRA. 