BACKGROUND: Measuring differential renal function (DRF) is critical for managing children with congenital and acquired urological diseases. MAG-3 renal scintigraphy is the most widely used clinical technique; dynamic contrast-enhanced MRI (DCE-MRI) provides a radiation-free and high-resolution alternative method for assessing DRF.

OBJECTIVE: To evaluate the agreement between DRF values derived from DCE-MRI and MAG-3 scintigraphy-derived DRF in pediatric patients.

MATERIALS AND METHODS: This retrospective study included 23 pediatric patients (age range, 3 months-20 years; mean±SD, 8.3±7.4 years) who underwent DCE-MRI embedded in MR urography (MRU) protocol and MAG-3 studies within 6 months. DCE-MRI was performed using a golden-angle radial dynamic stack-of-stars acquisition with golden-angle sparse parallel (GRASP) reconstruction, and analyzed the renal filtration rate with a two-compartment tracer kinetic model. DRF values from DCE-MRI were compared with those from MAG-3, using both default (n=23) and C-shaped background regions for MAG-3 analysis, where raw data were available (n=16). Agreement was evaluated using Bland-Altman analysis, Pearson and concordance correlations, and paired statistical tests.

RESULTS: With default MAG-3 background analysis (n=23), mean DRF difference (MAG-3 minus DCE-MRI) was 0.4% (95% CI, -3.3% to 4.2%), with 95% limits of agreement of -16.7% to +17.5%. Concordance correlation coefficient (CCC) was 0.870 (95% CI, 0.718-0.942). Within the pre-defined clinically acceptable margin of ±10%, 78.3% (18/23) of cases fell, with a mean absolute difference of 6.1%. With C-shaped background subtraction in the subset with available raw MAG-3 data (n=16), mean difference was -2.3% (95% CI, -6.7% to 2.0%), limits of agreement -18.3% to +13.6%, and CCC 0.845 (95% CI, 0.614-0.943). Pearson correlation was strong in both analyses (n=23: r=0.872, 95% CI, 0.719-0.945; n=16: r=0.866, 95% CI, 0.648-0.953; both P<0.001). No clinically significant systematic or proportional bias was detected in either analysis.

CONCLUSION: DCE-MRI demonstrates strong linear association and concordance with MAG-3 scintigraphy for pediatric differential renal function assessment with no clinically significant systematic bias, though the observed measurement variability indicates caution is warranted when comparing values near surgical decision thresholds. C-shaped background correction is recommended for MAG-3 in hydronephrotic kidneys to optimize inter-modality agreement.