Correlation of Renal Oxygenation with Renal Function in Chronic Kidney Disease: A Preliminary Prospective Study

Abstract

<b><i>Introduction:</i></b> 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. <b><i>Methods:</i></b> 97 non-dialysis patients with CKD stages 1–5 and healthy volunteers (HVs) were recruited in the study, all participants without diabetes. Based on their estimated glomerular filtration rate (eGFR), the patients were divided into two groups: CKD stages 1–3 (CKD 1–3) and CKD stages 4–5 (CKD 4–5). 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 was determined. <b><i>Results:</i></b> The COT2* values were significantly higher than MET2* values in all participants. The COT2* and MET2* values of three groups were ranked as HV &gt; CKD 1–3&gt; CKD 4–5 (<i>p</i> &lt; 0.0001). There were positive correlations between the COT2* values, MET2* values and eGFR, hemoglobin (<i>r</i> &gt; 0.4, <i>p</i> &lt; 0.01). The 24-h urinary protein (24-h Upr) showed weak correlation with the COT2* value (<i>r</i>_s = −0.2301, <i>p</i> = 0.0265) and no correlation with the MET2* value (<i>p</i> &gt; 0.05). Urinary microprotein, including urinary alpha1-microglobulin, urinary beta2-microglobulin (β2-MG), and urinary retinol-binding protein (RBP), showed strong correlation with COT2* and MET2* values. According to the analysis of receiver operating characteristic curve, the optimal cut-points between HV and CKD 1–3 were “&lt;61.17 ms” (sensitivity: 91.23%, specificity: 100%) for COT2* values and “&lt;35.00 ms” (sensitivity: 77.19%, specificity: 100%) for MET2* values, whereas COT2* values (“&lt;47.34 ms”; sensitivity: 90.00%, specificity: 92.98%) and MET2* values (“&lt;25.09 ms”; sensitivity: 97.50%, specificity: 80.70%) between CKD 1–3 and CKD 4–5. <b><i>Conclusion:</i></b> The decline of renal oxygenation reflected on T2* values, especially in cortex, may be an effective diagnostic marker for early detection of CKD.