Noninvasive Assessment of the Renal Function, Oxford Classification and Prognostic Risk Stratification of IgAN by Using Intravoxel Incoherent Motion Diffusion‐Weighted Imaging and Blood Oxygenation Level‐Dependent MRI

Background Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Oxford classification including mesangial hypercellularity (M), endothelial hypercellularity (E), segmental sclerosis (S), interstitial fibrosis/tubular atrophy (T), and crescent (C) were recommended to predict the prognosis of IgAN. Purpose To explore whether multiparametric magnetic resonance imaging (MRI) can be applied to assess the renal function, Oxford classification, and risk of progression to end‐stage kidney disease within 5 years of IgAN. Study Type Prospective. Population A total of 46 patients with pathologically confirmed IgAN and 20 healthy volunteers. Field Strength/Sequence A 3‐T, blood oxygenation level‐dependent (BOLD)‐MRI, intravoxel incoherent motion diffusion‐weighted imaging (IVIM‐DWI). Assessment Two radiologists measured the cortex and medulla T2*, apparent diffusion coefficient (ADC), true diffusion (Dt), pseudo‐diffusion (Dp), perfusion fraction (fp). All participants were divided into three groups: group 1, healthy volunteers; group 2, patients with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m 2 ; group 3, patients with eGFR <60 mL/min/1.73 m 2 . Or two groups: group A, 5‐year risk scores ≤10% and group B, 5‐year risk scores >10%. Statistical Tests Intraclass correlation coefficient, one‐way analysis of variance, least‐significant difference, Student's t‐test, Pearson product–moment correlation, Spearman's rank correlation, and receiver operating characteristics (ROC) with the area under the curve (AUC). A P value <0.05 was considered statistically significant. Results Except for cortical Dp, all other MRI parameters showed significant differences between group 1 and group 2. None of the MRI parameters showed a significant correlation with M, E, or C scores. Cortical T2*, Dt, fp, and medullary Dt and fp showed low‐to‐moderate significant correlations with S scores. Except for cortical and medullary Dp, all other MRI parameters were significantly correlated with T scores. Cortical Dt showed the largest AUC for differentiating group A from group B (AUC = 0.927) and T0 from T1/T2 (AUC = 0.963). Data Conclusion Imaging by IVIM‐DWI and BOLD‐MRI could facilitate noninvasive assessment of the renal function, Oxford classification, and prognostic risk of IgAN patients. Evidence Level 2. Technical Efficacy Stage 3.