<b><i>Introduction:</i></b> The basic pathophysiologic derangement of chronic kidney disease (CKD) begins with the loss of nephrons, leading to renal hemodynamic changes, eventually causing a reduced nephron count and renal hypoxia. The purpose of this study was to observe the renal oxygenation and renal hemodynamics of patients with CKD using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) and intrarenal Doppler ultrasonography (IDU). <b><i>Methods:</i></b> The study enrolled 39 patients with stage 1–4 CKD and 19 healthy volunteers (HVs). Based on their estimated glomerular filtration rate (eGFR), CKD patients were divided into 2 subgroups: a mild renal impairment (MI) group and a moderate to severe renal impairment (MSI) group. We monitored the participants’ mean cortical T2* (COT2*) and mean medullary T2* (MET2*) values on BOLD-MRI, and measured the peak systolic velocities (PSVs), end-diastolic velocities (EDVs), renal resistive index (RI), and kidney length by IDU. We also recorded clinical indicators such as age, sex, body mass index (BMI), 24-h urinary protein (24-h Upr), serum creatinine (sCr), blood urea nitrogen (BUN), and eGFR. BOLD-MRI, IDU measurements, and the clinical indicators were compared in CKD patients and HVs by the analysis of variance and Kruskal-Wallis <i>H</i> test. Spearman’s correlation was used to assess the relationship between data from BOLD-MRI and IDU and clinical indicators. <b><i>Results:</i></b> The COT2* values were significantly higher than the MET2* values in the HV, MI, and MSI groups. COT2*, MET2*, EDV, PSV, and kidney length gradually decreased in the HV, MI, and MSI groups (all <i>p &#x3c;</i> 0.05), whereas RI and 24-h Upr gradually increased (both <i>p</i> &#x3c; 0.05). Spearman correlation analysis showed that COT2* and MET2* were significantly positively correlated with eGFR, PSV, EDV, and kidney length but were significantly negatively correlated with sCr, BUN, and 24-h Upr (all <i>p</i> &#x3c; 0.05). There was no correlation observed between the COT2* and MET2* and the RI and BMI values. <b><i>Conclusions:</i></b> Renal oxygenation and blood flow velocities were found declined as the CKD stage progressed. The BOLD-MRI and IDU techniques may have clinical value by measuring intrarenal oxygenation and renal blood perfusion to judge the severity of renal damage in patients with CKD.

Introduction: 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 CKD stages 1-5 and healthy volunteers (HVs) were recruited in the study. 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 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> CKD 1-3> CKD 4-5 (p< 0.0001). There were positive correlations between the COT2* values, MET2* values and eGFR, hemoglobin (r> 0.4, p< 0.01). The 24-h urinary protein (24-h Upr) shown weak correlation with the COT2* value (rs= -0.2301, p= 0.0265), and no correlation with the MET2* value (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 CKD 1-3 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 CKD 1-3 and CKD 4-5. Conclusion: The decline of renal oxygenation reflected on T2* values, especially in cortex, may be an effective diagnostic-marker for early detection of CKD.

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< 0.0001). There were positive correlations between the COT2* values, MET2* values and eGFR, Hemoglobin (r> 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< 0.0001). The 24-h urinary protein (24-h Upr) shown weak correlation with the COT2* value (rs= -0.2301, p= 0.0265), and no correlation with the MET2* value (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.