QUANTITATION OF RENAL PARENCHYMAL RETENTION OF TECHNETIUM-99M-MAG3 INRENAL-TRANSPLANTS

When imaging renal transplants with tubular agents, such as mercaptoac etyltriglycine, marked parenchymal retention is a hallmark of acute re jection (AR) or acute tubular necrosis (ATN). OAR can be distinguished from ATN by the time course on serial studies.) The quantitative rela tionship of retention to uptake can be measured by dividing the backgr ound-corrected renal activity at 20 min by that at 3 min. Methods: The diagnostic value of this ratio (R(20/3)) was tested in a series of 55 5 renograms. Because patients with mild disease have minimal abnormali ties, the patients were ranked by their estimated severity of disease (1-4 for abnormal and 0 for normal). Results: R(20/3) was found to cor relate strongly with severity of ATN (Spearman's p = 0.879, p < 0.001, n = 168) and also with severity of AR (p = 0.888, p < 0.001, n = 267) . There were two (3%) false-positive results in 64 normal patients. Co nclusion: If 0.8 is taken as the upper limit of normal for R,,, then a mong patients with disease severity 3 or 4, there were no false-negati ve findings in 104 patients with ATN or in 203 patients with AR. R(20/ 3) despite its simplicity, is an effective diagnostic parameter.