Renal MRI Imaging Features In Patients With Type 2 Diabetic Kidney Disease

Objective:This study aims to evaluate the changes of renal oxygenation level,water molecular diffusion level and renal microstructure by using two functional magnetic resonance imaging techniques（f MRI）in patients with type 2 diabetic kidney disease,and analyze the correlations between the changes of R2^*/FA/ADC value and clinical biochemical indicators.We hope to demonstrate that BOLD and DTI can be novel,effective and noninvasive methods for the diagnosis and evaluation of diabetic kidney disease.The study includes two parts.Methods:A total of 122 diabetic patients and 28 sex-and age-matched healthy volunteers were recruited from the Department of Nephrology and Endocrinology from December 2020 to November 2022.In 122 diabetic patients,20 patients with non-diabetic kidney disease（NDKD）were included.The remaining 102 diabetic patients were divided into three groups according to urinary albumin/creatinine ratio（UACR）and eGFR:normal group,simple microalbuminuria group,simple macroalbuminuria group,simple decreased eGFR group and albuminuria with decreased eGFR group.Clinical biochemical indicators,especially renal function related indicators such as serum creatinine and serum CysC,were collected within 24hours after MRI examination.All MRI scans were performed on a 3.0T Discovery MR750w machine.The first part of the scan includes conventional T₁,T₂sequence and coronal MFGRE sequence of BOLD scanning,which is divided into two breath-hold scans for a total of 27 seconds;the second part is DTI sequence SE-EPI scan,the breath-triggered technique requiring no breath-holding with b value（0,600s/mm²）.16 directions of diffusion-sensitive gradient pulse were applied,and the acquisition time was 37-46 s.The cortical R2^*/FA/ADC values and medullary R2^*/FA/ADC values were measured respectively.The research contents were as followed.（1）The general data,clinical biochemical indexes and pathological data of the subjects were collected,and the statistical differences of the above data were compared between the groups.（2）The morphological differences of the kidneys in MRI images of all subjects were analyzed quantied by CMD.（3）The consistency of R2^*,FA and ADC values in both kidneys of all subjects was analyzed,the R2^*,FA and ADC values of renal cortex and medulla were measured,and the statistical differences among groups were compared.（4）ROC curve was drawn to analyze the diagnostic efficacy of R2^*/FA value of renal medulla and the two combined indicators in early DKD.（5）Spearman coefficient was calculated between R2^*value,ADC,FA value and clinical biochemical indexes,and independent risk factors of medulla hypoxia and microstructural destruction were analyzed by multiple linear regression method.（6）The general data,clinical biochemical indexes,pathological data and MRI data of DKD and NDKD patients were analyzed,and compared.Results:A total of 122 diabetic patients and 28 healthy people were included.All diabetic patients were divided:26 cases in normal group,28 cases in simple microalbuminuria group,17 cases in simple macroalbuminuria group,16 cases in simple decreased eGFR group,15 cases in albuminuria with decreased eGFR group and 10 cases in NDKD group.The results showed that（1）there was no significant difference between healthy control group and diabetes group with different GA grades（p>0.05）.There were no significant differences in sex ratio,age,blood pressure and duration of DM among the groups（p>0.05）,while there were significant differences in BMI,duration of hypertension,hemoglobin,fasting blood glucose,TG/LDL-C,BUN,CysC,UA,Scr,eGFR,UAlb and UACR among different groups（p<0.05）.The expression rate of HIF-1αwas 85.7%in the pathological tissues of 21 DKD patients.HIF-1αwas not expressed in the control group with minimal change disease（MCD）.The expression of HIF-1αwas correlated with the pathological grade of DKD,eGFR level and UACR grade.（2）Clear corticomedullary differentiation was observed in the healthy control group on the T₁WI map of axial FSPGR.The degree of CMD was different in diabetic patients（p<0.05）.The oxygenation levels in left and right kidneys were consistent in all subjects.The ADC and FA between left and right kidneys were significantly different（p<0.05）.The measured values of left kidneys were more affected by the heart and blood vessels.（3）R2^*value of cortex was significantly lower than that of medulla in all groups（p<0.05）,but there was no significant difference in the R2^*value of cortex among all groups（p>0.05）,while the R2^*value of medulla among all groups was significantly different（p<0.05）.The MR2^*value of simple microalbuminuria was significantly different from that in simple macroalbuminuria group and simple decreased eGFR group（p=0.003;p=0.001）;The MR2^*value in normal group was lower than that in simple microalbuminuria group（p=0.011）,and the MR2^*value insimple macroalbuminuria group was higher than that in simple microalbuminuria group（p=0.026）.Cortical FA value was significantly lower than medullary FA value in all groups（p<0.05）.Cortical ADC value was significantly higher than medullary ADC value（p<0.05）.But there was no significant difference in cortical FA value,cortical ADC value and medullary ADC value among all groups（p>0.05）.Only the FA value of medulla was significantly different（p<0.05）.The medullary FA value in healthy people was significantly different from patients with albuminuria or decreased eGFR（p<0.01）.Among diabetic groups,the medullary FA value in mormal group was significantly different from that in simple microalbuminuria group,and the FA value of medulla in simple decreased group was significantly different from that in simple microalbuminuria or simple macroalbuminuria group（p=0.016;p=0.021）.（4）The medullary R2^*and FA values and the two combined indicator performed well in the diagnosis of early DKD（p<0.05）.（5）The R2^*value of medulla was significantly correlated with clinical indicators such as hemoglobin,serum creatinine,urea nitrogen,cystatin C,uric acid,eGFR,urinary microalbumin and UACR（p<0.05）.There were significant correlations between medulla FA value and clinical indicators such as hemoglobin,serum creatinine,urea nitrogen,cystatin C,uric acid,UA,eGFR value and UACR（p<0.05）.Multiple linear regression analysis（stepwise method）showed that eGFR level was independently correlated with MR2^*,and serum Scr,CysC,eGFR were independently correlated with medullary FA（p<0.05）.（6）The proportion of DKD accompanied with diabetic retinopathy was relatively high.The duration of DM in NDKD group was relatively short,and the degree of UACR was relatively low.With the aggravation of renal albuminuria in diabetes,the MR2^*value showed that renal oxygenation level was much more affected in DKD patients.When eGFR was normal,the degree of renal hypoxia in DKD was significantly higher than that in NDKD.Conclusion:Functional MRI can reveal the changes or progression of renal function in patients with diabetic kidney disease from the aspects of oxygenation level,and renal microstructure to reflect the pathophysiological characteristics of DKD.Medullary R2^*and FA values can be used in the diagnosis of diabetic kidney disease and the evaluation of renal function,which have high clinical value as novel imaging markers for the future study of DKD.