Detection of split renal function with MRI: Arterial spin labeling combined with renal structure imaging in obstructive nephropathy

Background Non-invasive monitoring of split renal function (SRF) impairment in the context of urinary tract obstruction remains challenging. Renal scintigraphy (RS), the clinical standard, involves ionizing radiation, whereas magnetic resonance imaging (MRI)-based alternatives are underexplored. Purpose To evaluate arterial spin-labeled (ASL) and structural MRI for SRF assessment in obstructive nephropathy. Material and Methods Consecutive patients underwent 3.0-T MRI (ASL/T1-weighted). Kidneys (n = 92) were stratified by scintigraphy-derived glomerular filtration rate (RS-GFR) into normal renal function, mild to moderate renal impairment, severe impairment, or no function groups. Cortical renal blood flow (RBF), parenchymal thickness (RPT), and hydronephrosis width (HW) were measured. Group differences (ANOVA/Kruskal-Wallis) and correlations with RS-GFR (Pearson/Spearman) were analyzed. Receiver operating characteristic curves assessed diagnostic performance. Results RBF, RPT, and HW differed significantly among groups ( P < 0.001), correlating strongly with RS-GFR (r = 0.767, 0.684, −0.589). They discriminated SRF subgroups ( P < 0.001); RBF + RPT + HW achieved areas under the curve of 0.869 (normal vs. mild), 0.883 (mild vs. severe), and 0.994 (normal vs. severe). Conclusion ASL-derived RBF and structural markers (RPT and HW) correlate robustly with RS-GFR, offering a feasible MRI-based, non-invasive approach for SRF monitoring.