PROSPECTIVE-STUDY OF SIMULTANEOUS ORTHOIODOHIPPURATE AND DIETHYLENETRIAMINEPENTAACETIC ACID CAPTOPRIL RENOGRAPHY

Captopril renography (CR) has been established in the past 10 yr as a useful diagnostic test for renovascular hypertension, However, direct comparison of tubular and glomerular tracers, quantitative criteria, c omparison of quantitative and qualitative results and the reliability of the results in renal failure have not been described in a systemati c, prospective fashion. Methods: Same-day baseline and CR using Tc-99m -labeled diethylenetriaminepentaacetic acid (DTPA) and [I-131]orthoiod ohippurate (OIH) were simultaneously performed in two groups of hypert ensive subjects, one with demographically defined essential hypertensi on (n = 43) and the other (n = 60) with a high prevalence of renovascu lar disease, defined with angiograms. Quantitative criteria for abnorm al CR were derived from results among the subjects with essential hype rtension. Qualitative analysis was performed using widely established criteria. Results: There were no statistically significant differences between quantitative and qualitative accuracy, between OIH and DTPA o r among quantitative parameters. The best accuracies for quantitative CR were 56% with DTPA (n = 57) and 60% with OIH (n = 60), in both case s using the relative renal uptake parameter, Qualitative CR (n = 60) h ad accuracies of 43% (DTPA) and 50% (OIH), both hindered by 29 (DTPA) and 25 (OIH) abnormal but nondiagnostic studies, Two false-positive st udies were detected, Twenty-seven of 29 nondiagnostic studies were ass ociated with a glomerular filtration rate of <50 ml/min (n = 17), one small kidney (n = 17) and/or bilateral renal artery stenosis (n = 16). Supplemental measurement of in vitro stimulated plasma renin activity insignificantly (p > 0.10) and improved accuracies to 63% (DTPA) and 70% (OIH), without introducing additional false-positive tests. Conclu sion: Orthoiodohippurate and DTPA have comparable accuracy in prospect ive simultaneous evaluation of CR. False-positive studies are fewer th an 5%, The accuracies of quantitative and qualitative criteria do not differ significantly but may be improved by supplemental use of the in vitro stimulated plasma renin activity. In individuals with renal ins ufficiency, small kidneys and/or bilateral renal artery disease, up to 48% of CR studies are abnormal but nondiagnostic.