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

UNLABELLED: Preliminary data suggest that aspirin renography is more sensitive than captopril renography for indicating renal artery stenosis (RAS). Considering that aspirin, compared with captopril, reduces renal blood flow and, thus, tubular tracer delivery in poststenotic kidneys, aspirin renography is expected to be more useful, particularly if tubular tracers are used.

METHODS: We prospectively compared aspirin renography (20 mg/kg orally) and captopril renography (25 mg orally) with 99mTc-mercaptoacetyltriglycine in 75 consecutive patients suspected of having RAS.

RESULTS: RAS, diagnosed as stenosis of more than 50% on angiography, was found unilaterally in 34 patients and bilaterally in 17 patients. RAS was absent in 24 patients. The sensitivities for unilateral RAS or bilateral RAS (i.e., stenosis that was at least unilateral) 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 significant). Tracer uptake ratios, time to peak activity, and percentage of 20-min tracer retention were also not significantly different for captopril and aspirin renography. Subgroup analysis of modest (50-75%) and severe (> or =75%) RAS, or of plasma creatinine greater than 120 micromol/L, also showed no difference between captopril and aspirin renography.

CONCLUSION: We conclude that for identification of RAS, the usefulness of aspirin renography equals, but does not surpass, that of captopril renography.