CAPTOPRIL RENAL SCINTIGRAPHY WITH TC-99M-MERCAPTOACETYLTRIGLYCINE (TC-99M-MAG3) FOR DETECTING RENAL-ARTERY STENOSIS

A recently developed radiopharmaceutical with favorable characteristics for renal studies, Tc-99m-mercaptoacetyltriglycine (Tc-99m-MAG3), was employed for renal scintigraphy in the detection of renal artery stenosis (RAS) in 102 hypertensive patients who underwent renal angiography within 4 weeks of scintigraphic assessment. Renal scintigraphy was performed with 120 MBq of Tc-99m-MAG3 60 min after oral administration of 50 mg captopril. Studies were evaluated for renogram shape, relative tracer uptake, time to peak counts, and parenchymal transit time. In cases of normal outcome, no further scintigraphic test was requested. In all other cases a baseline study was performed within 2 to 3 days. Where an apparent improvement was found in baseline conditions compared to the provocative test (upslope of the renogram, increased tracer uptake, and reduction of parenchymal transit time), the study was considered positive for significant RAS. At renal angiography, 48 arteries were found affected by RAS > 50% and 27 by RAS < 50%. Sensitivity and specificity for detection of RAS > 50% were 89.6% and 91.6%, respectively. In kidneys affected by RAS > 50%, captopril administration typically induced a prolongation in parenchymal transit time (324 +/- 90 sec, baseline conditions, v 408 +/- 122 sec, postcaptopril, P < .01) as against 255 +/- 70 v 251 +/- 64, P = NS, in kidneys supplied by patent arteries or with RAS < 50%.