Noninvasive Evaluation of Renal Hypoxia by Multiparametric Functional MRI in Early Diabetic Kidney Disease.

BACKGROUND Renal hypoxia, which caused by a mismatch between oxygen delivery and oxygen demand, may be the primary pathophysiological pathway driving diabetic kidney disease (DKD). Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) could detect hypoxia, but can be limited in distinguishing increased oxygen consumption or decreased blood supply. PURPOSE To explore multiparametric functional MRI in evaluating mechanism of the hypoxia changes in early stage of DKD. STUDY TYPE Prospective. ANIMAL MODEL Thirty-five New Zealand White rabbits were divided into control group (n = 5) and alloxan-induced diabetes mellitus (DM) groups (DM3 group: n = 15, DM7 group: n = 15). FIELD STRENGTH/SEQUENCE 3 T MRI/BOLD, arterial spin labeling (ASL), and asymmetric spin-echo (ASE). ASSESSMENT The renal oxygenation level (R2*), renal blood flow (RBF), and oxygen extraction fraction (OEF) were evaluated by BOLD, ASL, and ASE MRI, respectively. The regions of interest were manually drawn including cortex, outer stripes of outer medulla (OS), and inner stripes of outer medulla (IS). STATISTICAL TESTS Analysis of variance, independent-sample t-test, and paired-sample t-test were applied for comparisons among groups, between groups, and within the same group. P < 0.05 was considered statistically significant. RESULTS All renal regions of DM3 group at Day 3 after DM induction showed significantly higher R2* and OEF values compared to baseline. The RBF values showed no statistically significant difference (P = 0.62, 0.76, 0.09 in cortex, OS, and IS, respectively). For DM7 group at Day 7, R2*, OEF, and RBF values showed no statistically significant difference compared to baseline (P = 0.06, 0.05, 0.06 of R2*; 0.70, 0.64, 0.68 of OEF; and 0.33, 0.58, 0.48 of RBF in cortex, OS, and IS, respectively). DATA CONCLUSION BOLD MRI could detect renal hypoxia in early stage of DKD rabbit model, which was mainly revealed by increased oxygen consumption, but not affected by renal blood flow change. LEVEL OF EVIDENCE 2 Technical Efficacy Stage: 1.