RESUMO
L,L-ethylenedicysteine [EC] is a new carrier of technetium Tc 99m [99mTc] with a lower affinity to plasma albumin in comparison with diethylenetriamine pentaacetic acid [DTPA]. We compared 99mTc-EC scan with 99mTc-DTPA scan in diuretic renography for patients with obstructive uropathy. Thirty-three patients with upper urinary tract obstruction were randomly selected and underwent diuretic renographies by 99mTc-EC and 99mTc-DTPA. The counts of radioisotope per pixel in the target [the kidney] and background tissues as well as the clearance half-life of these two radiopharmaceuticals were measured and compared. Mean counts of radioisotope per pixel in the target tissue was not different between 99mTc-EC and 99mTc-DTPA scans, but in the background tissue, it was less for 99mTc-EC [P =.003]. Target-background ratio was higher for 99mTc-EC scan [3.80 +/- 2.11 versus 2.48 +/- 1.39; P <.001]. Renal clearance half-life of radioisotope was shorter for 99mTc-EC scan than 99mTc-DTPA scan [58.15 +/- 15.17 minutes versus 78.65 +/- 19.99 minutes; P =.033]. The results were similar for uremic patients [with a serum creatinine level > 2mg/dL]. Target-background ratio of radiopharmaceutical uptake rates in diuretic renography was a good indicator of the higher resolution of 99mTc-EC than 99mTc-DTPA scan. We also demonstrated the faster clearance of 99mTc-EC than 99mTc-DTPA. This results in less radiation that is especially useful in children. To our opinion, 99mTc-EC can better depict the kidneys in comparison with 99mTc-DTPA