Split renal function in young children with unilateral pelvi-ureteric junction obstruction using [99m]Tc-DTPA or [99m]Tc-MAG[3]

ABSTRACT

Cases of unilateral hydronephrosis in pediatric patients are mostly due to pelvi-ureteric junction obstruction [PUJO] that causes hindrance in the drainage of urine outflow, leading to kidney function impairment The impaired excretory drainage is expected to have diminished or normal split renal function [SRF] on the affected side. However, in a significant number of patients with severe PUJO an elevated SRF can be found. The aim of this work was to estimate the frequency of various grades of SRF in children with PUJO. Secondly, to find out whether there is a difference between [99m]Tc-DTPA or[99m]Tc-MAG3 in assessing the SRF in these children. Fifty-eight children with unilateral PUJO referred for dynamic renography were included in this study on retrospective basis. Twenty-four patients underwent dynamic renography using [99m]Tc-DTPA while 34 were evaluated using [99m]Tc-MAG3. For both [99m]Tc-DTPA and [99m]Tc-MAG3, the dynamic renography started by perfusion phase [1 frame/ sec for 1 min] followed by 15-sec frames for 29 minutes. In all patients frusemide was given at a dose of 1mg/kg at 10 minutes post injection, In the DTPA and MAG3 studies, glomerular filtration rate [GFR] and renal plasma flow [ERPF] were estimated respectively and SRF was calculated from both figures. The normal range for SRF was considered 45% to 55%, In all patients, diagnostic ultrasound was done prior to isotopic renography. The mean age of the studied children was 18 +/- 10 months. The children in the DTPA and MAG3 groups were age and sex-matched. In the DTPA group 25% of the patients had a diminished SRF [< 45%], [46%] had normal SRF and 29% showed paradoxical SRF [> 55%]. In the MAG3 group, 32% of patients had diminished SRF, 41% had normal SRF and 26% showed paradoxical SRF of > 55%. There was no significant difference between DTPA and MAG3 in estimation of SRF in those with normal and suprnormal SRF [P value = 0.0865 and 0,094 respectively] however MGA3 tends to be superior to DTPA in cases of impaired renal function [P value < 0.05. The obstructive renogram patterns define the functional significance of the various grades of hydronephrosis detected by ultrasound. Both [99m]Tc-MAG3 and [99m]Tc-DTPA are comparable and can estimate the SRF in young children with unilateral PUJO, however, in cases of impaired renal function [99m]Tc-MAG3 tends to be better than [99m]Tc-DTPA. Impaired and Paradoxical supranormal split renal function are significantly present in young children with unilateral PUJO