Correlation of renal oxygenation with renal function in chronic kidney disease: a preliminary prospective study

Background: Chronic hypoxia is prevalent in chronic kidney disease (CKD), and Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) provides noninvasive evaluation of renal oxygenation. This study aimed to explore the correlation of renal oxygenation evaluated by BOLD-MRI with renal function. Methods: : 97 non-dialysis patients with stage 1-5 CKD and healthy volunteers (HVs) recruited in the study. Base on their estimated glomerular filtration rate (eGFR), the patients were divided into two groups: the mild to moderate renal injury (MMI) group and severe renal injury (SI) group. We measured cortical and medullary T2* (COT2* and MET2*) values in all participants by BOLD-MRI. Physiological indices were also recorded and compared among three groups. Correlation of T2* values with clinical characteristics were determined. Results: : The COT2* values were significantly higher than MET2* values in all participants. The COT2* and MET2* values of three groups were ranked as HV> MMI> SI (p 0.4, p< 0.01), while the serum creatinine (SCr), blood urea nitrogen (BUN) and serum cystatin C (Cys C) were significantly negatively correlated with the COT2* and MET2* values (r< -0.7, p 0.05). Urinary microprotein, including urinary alpha1-microglobulin (α1-MG), urinary beta2-microglobulin (β2-MG), and urinary retinol binding protein (RBP), was showed strong correlation with COT2* and MET2* values. According to analysis of receiver-operating characteristic (ROC) curve, we obtained the optimal cut-point between HV and MMI were “< 61.17 ms” (sensitivity: 91.23%, specificity: 100%) for COT2* values and “< 35.00 ms” (sensitivity: 77.19%, specificity: 100%) for MET2* values, whereas COT2* values (“< 47.34 ms”; sensitivity: 90.00%, specificity: 92.98%) and MET2* values (“< 25.09 ms”; sensitivity: 97.50%, specificity: 80.70%) between MMI and SI. Conclusion: The decline of renal oxygenation reflected on T2* values, especially in cortex, may be an effective diagnostic-marker for early detection of renal injury in CKD patients.