OBJECTIVE Prostaglandins play important roles in renal physiology and in the development of renovascular hypertension. In a recent study, inhibition of renal prostaglandin synthesis was found to be useful for detecting renovascular hypertension using renal scintigraphy. In the current study, the authors evaluated the role of aspirin (an inhibitor of prostaglandin synthesis) and compared it with Tc-99m DTPA captopril renal scintigraphy (CS). METHODS Twenty-five patients were examined with Tc-99m DTPA in a three-step manner: a baseline study, CS, and aspirin scintigraphy (AS). Each scintigraphic study was interpreted visually and according to the renogram curve patterns. Semiquantitative parameters (Tmax, renal indices [%], 20-minute/max count ratio, glomerular filtration rate) were also calculated. Plasma renin activity was determined for each study. The blood pressures of all patients were measured during AS. All patients had a contrast-enhanced angiogram that was used as the reference test. RESULTS Three groups of patients were observed based on the scintigraphic and angiographic results. In each group, no difference was observed in blood pressure after aspirin administration. In group 1, seven patients had normal angiographic and scintigraphic results. In group 2, eight patients had angiographically confirmed renal artery stenosis (RAS). In 6 patients (mean, 47% RAS), both AS and CS were negative for RVH. In the remaining two patients with RAS (mean, 83% stenosis), the kidneys were atrophic on the stenotic side, and thus the kidneys did not respond to the interventions. No difference was observed in plasma renin activity in groups 1 and 2. Group 3 included 10 patients who had angiographically confirmed RAS (mean, 86%). In 9 patients, both CS and AS were positive for RVH. In the remaining one patient, scintigraphic results were falsely negative. Statistical analyses performed for semiquantitative parameters did not reveal any significant difference in this group, although there was a tendency toward prolonged Tmax values after captopril and aspirin administration. In four cases, unexpected elevation of plasma renin activity was observed in group 3. CONCLUSIONS These data indicate that AS with Tc-99m DTPA is an alternative for CS. It has the advantage of having no effect on blood pressure and does not require that angiotensin-converting enzyme inhibitors be discontinued. Although in this study 9 of 10 patients had correct diagnoses of RAS, further studies, especially using tubular agents with the calculation of parenchymal transit time, might provide valuable information in this patient group. An ongoing study is being performed in the authors' institute.