Evaluation of split renal function using MR-derived structure and arterial spin-labeled perfusion features in obstructive nephropathy

Objectives To explore the value of renal arterial spin-labeled (ASL) and structural MRI in evaluating split renal function (SRF) by renal scintigraphy (RS) in obstructive nephropathy. Materials and methods Consecutive patients with obstructive hydronephrosis were recruited for a 3.0-T conventional and ASL examination from January 2022 to August 2023 prospectively. The 92 independent kidneys were classified into normal renal function, mild to moderate renal impairment, severe renal impairment, or no function groups. Renal blood flow (RBF), renal parenchymal thickness (RPT), and renal pelvic dilatation (RPD) were assessed based on ASL and T1WI maps. One-way analysis of variance (ANOVA) and Kruskal-Walli’s test were used to analyze the differences. Pearson and Spearman rank correlation analysis approaches were adopted to analyze the correlation between RBF, RPT, RPD, and glomerular filtration rate (GFR) by RS. The ROC curve was used to compare their performance in SRF evaluation. Results Renal cortical RBF, RPT, and RPD could distinguish SRF pairwise subgroups with different renal function impairments ( p <0.001), with correlation coefficients of 0.767, 0.635, and -0.589, respectively (all p <0.001). RBF combined with RPT and RPD achieved the best efficacy in distinguishing between normal and mild, mild and severe, normal and severe renal dysfunction, with AUCs of 0.869 (95% CI, (0.768-0.937)), 0.883 (95% CI, (0.756-0.959)) and 0. 994 (95% CI, (0.931-1.00)). Conclusions MR structural features and ASL imaging enable quantitative measurements of RPT, RPD, and renal cortical RBF, which were correlated with RS-GFR. MR combination demonstrated clinical potential in noninvasive evaluation of SFR in obstructive nephropathy.