Technetium-99m-L,L-ethylenedicysteine scintigraphy in patients with renal disorders

Technetium-99m-L,L-ethylenedicysteine (^99mTc-L,L-EC), a new renal imaging agent, was introduced as an alternative to^99mTc-mercaptoacetyltriglycine (MAG3). This radiopharmaceutical can be easily labelled at room temperature and has high radiochemical purity and long stability. The aim of this study was to gain clinical experience in using^99mTc-L,L-EC in normal volunteers and patients. The clearance of this radiopharmaceutical was compared with that of iodine-131ortho-iodohippurate (OIH) in five healthy volunteers. In addition, conventional renogram and whole-body distribution of^99mTc-L,L-EC (40 min and 3 h post-injection) were evaluated in these subjects. Subsequently, ten patients with suspected obstructive nephropathy, four with renovascular disorders and two in acute renal failure were imaged. In five patients with impaired renal function both^99mTc-MAG3 and^99mTc-L,L-EC studies were performed. In each case the scintigraphic images and time/activity curves were evaluated and various semiquantitative parameters calculated and compared. No adverse effects were noted during and after^99mTc-L,L-EC scintigraphy. The mean clearance values for^99mTc-L,L-EC and¹³¹I-OIH in volunteers were 504 and 663 ml/min respectively. The total plasma clearance of^99mTc-L,L-EC was about 75.8% of the¹³¹I-0IH value. In volunteers the parenchymal transit time index, whole kidney transit time index and mean parenchymal transit time for^99mTc-L,L-EC were 63 s, 124 s and 175 s respectively. The mean time to peak activity was 235 s and the time from peak to 50% of peak activity was 402 s. In all patients the results of scintigraphy were concordant with clinical findings and subsequently influenced patient management. Furthermore,^99mTc-L,L-EC scintigraphy provided high-quality images similar to those obtained with^99mTc-MAG3, even at low glomerular filtration rates (18 ml/min). It is concluded that^99mTc-L,L-EC has excellent imaging characteristics similar to^99mTc-MAG3 and excretion properties similar to OIH. This radiopharmaceutical can be used routinely to evaluate patients with renal disorders.