The accuracy of different calculated methods using 99mTc-DTPA dynamic scintigraphy for split renal function estimation. Comparison with standard 99mTc-DMSA renal scan

1737 Objectives To investigate whether any difference exists between split renal function (SRF) obtained by routinely used posterior 99mTc-DTPA scan and that obtained from 99mTc-DTPA dual head scan compared with SRF obtained from the standard 99mTc-DMSA scan in different renal disorders. Methods This prospective study includes 121 patients [44 females and 77 males; mean age 3.4±21.2 years]. According to 99mTc-DTPA dynamic renogram results, patients were divided into: obstructed group (66 patients) with unilateral or bilateral obstructed outflow tract; normal group (20 patients); renal impairment group (10 patients) and pediatric age group (25 patients). Dual-head 99mTc-DTPA dynamic renal scans and 99mTc-DMSA static renal scans were performed for all patients. SRF was calculated for Rt and Lt kidneys and the difference between Rt and Lt SRF from posterior scans and anterior scans to calculate the average Rt and Lt kidneys SRF as well as the difference between Rt and Lt kidneys average SRF. These parameters were then statistically compared and correlated with the SRF of Rt and Lt kidneys and the difference between them obtained from the standard geometric mean of 99mTc-DMSA static scan. Results No significant statistical difference (p>0.05) could be found on comparing the mean values of the SRF quantitative parameters between 99mTc-DTPA-POST as well as 99mTc-DTPA-Average compared to the same SRF parameters calculated from 99mTc-DMSA scans in the four groups of patients. In correlation analysis, a high significant correlation between the SRF obtained from the 99mTc-DMSA and SRF obtained from both 99mTc-DTPA-POST and 99mTc DTPA-Average, for left and right kidneys as well as for the difference in split functions. Bland-Altman graphs in each studied group showed perfect agreement of 99mTc-DTPA-POST method and 99mTc- DTPA-Average method with the 99mTc-DMSA method in respect to SRF calculation. Conclusions Based upon our findings, we have concluded that, whenever an accurate calculation of split renal function is needed in different renal disorders, the routinely done 99mTc-DTPA dynamic scan using either single or dual head protocols can provide reliable measures of SRF similar to the standard 99mTc-DMSA renal scan. This would lead to considerable savings in time, cost and radiation burden especially in pediatric age group.