Aspirin renography and captopril renography in the diagnosis of renal artery stenosis

Preliminary data suggest that aspirin renography is more sensitive than cap topril renography for indicating renal artery stenosis (RAS). Considering t hat aspirin, compared with captopril, reduces renal blood flow and, thus, t ubular tracer delivery in poststenotic kidneys, aspirin renography is expec ted to be more useful, particularly if tubular tracers are used. Methods: W e prospectively compared aspirin renography (20 mg/kg orally) and captopril renography (25 mg orally) with Tc-99m-mercaptoacetyltriglycine in 75 conse cutive patients suspected of having RAS. Results: RAS, diagnosed as stenosi s of more than 50% on angiography, was found unilaterally in 34 patients an d bilaterally in 17 patients. RAS was absent in 24 patients. The sensitivit ies for unilateral RAS or bilateral RAS (i.e., stenosis that was at least u nilateral) were, respectively, 88% and 88% for captopril renography and 82% and 94% for aspirin renography (not significant). The overall specificity was 75% for captopril renography and 83% for aspirin renography (not signif icant). Tracer uptake ratios, time to peak activity, and percentage of 20-m in tracer retention were also not significantly different for captopril and aspirin renography. Subgroup analysis of modest (50-75%) and severe (great er than or equal to 75%) RAS, or of plasma creatinine greater than 120 mu m ol/L, also showed no difference between captopril and aspirin renography. C onclusion: We conclude that for identification of RAS, the usefulness of as pirin renography equals, but does not surpass, that of captopril renography .