Comparison of differential renal function using technetium-99m mercaptoacetyltriglycine (MAG3) and technetium-99m dimercaptosuccinic acid (DMSA) renography in a paediatric population

Background In children who have undergone both 99m Tc-DMSA and 99m Tc-MAG3 studies for the assessment of differential renal function (DRF) and drainage, respectively, we have noticed good agreement between the calculated DRF values, and hypothesized that there is no significant difference in DRF values calculated from these tests. Therefore, both tests may not always be necessary. Objective To determine whether there is a statistically significant difference between DRF values calculated using 99m Tc-DMSA and those calculated using 99m Tc-MAG3. Materials and methods We retrospectively identified children imaged with 99m Tc-DMSA and 99m Tc-MAG3. We recorded DRF values, age, indication, and renal pelvis diameter. For the 99m Tc-DMSA studies we recorded the imaging time after injection. For the 99m Tc-MAG3 studies we recorded the delay between injection and data acquisition, diuretic use and evidence of delayed drainage or reflux. Results We identified 100 episodes in 92 children where both 99m Tc-DMSA and 99m Tc-MAG3 scans had been performed within a few days. The commonest indication was urinary tract infection or pelviureteric junction obstruction. The mean age of the children was 6.96 years. A significant but clinically acceptable trend was seen between abnormal DRF and difference between tests. A significant link was found with the difference between tests and the time of imaging after DMSA injection, and also with scarring. No significant effect was caused by renal pelvis dilatation, delayed drainage, frusemide administration, or delayed 99m Tc-MAG3 imaging. Conclusion If a 99m Tc-MAG3 study has been performed then a 99m Tc-DMSA study is unnecessary provided DRF is normal on the 99m Tc-MAG3 study and there is no scarring. A change in practice would lead to considerable savings in time, cost and radiation burden.