Value Of Functional Magnetic Resonance Imaging In Prognosis Of Diabetic Kidney Disease

BACKGROUDDiabetic Kidney Disease(DKD),the leading cause of chronic kidney disease(CKD)and end-stage renal disease(ESRD),brings a huge burden to both the individual and society,therefore,effective monitoring of renal function and prognosis has great significance to improve the survival period of patients with DKD.Whereas,common clinical methods are deficiency in practice.The challenge of identifying the outcomes of DKD is intensified by the lack of a reliable biomarker for a long time,fortunately,recent advances in radiology have illuminated the possibility of fMRI to face the challenge.Blood oxygen level-dependent(BOLD)MRI,using deoxyhemoglobin as an endogenous marker.The higher renal deoxyhemoglobin corresponds to the higher the apparent relaxation rate R2*value which suggests the lower renal tissue oxygenation.Intravoxel incoherent motion diffusion-weighted image(IVIM-DWI)capitalizes on the different diffusion features of water molecules in fibrotic or nonfibrotic tissue.The decrease of pure water molecular diffusion D value companies with the increase of interstitial fibrosis.With the exploration of BOLD or DWI,their potential roles of renal dysfunction prediction have been noticed.Since most of the previous results based on short-term cross-sectional studies,and not using two techniques simultaneously.Whether fMRI values could discriminate prognosis in DKD have not been conclusively demonstrated.As such,this prospective cohort study was designed to reveal the efficiency of integrating BOLD-MRI and IVIM-DWI to evaluate the outcomes of DKD with follow up to fill the gap in this field.Although the applications have been performed in many centers worldwide,the results were inconsistent.The lack of a reliable method to acquire MRI datum may be one of the reasons.A novel semi-automatic technique which divides the kidney parenchyma into 12 layers of equal thickness was applied to reduce bias.METHODSThe study investigated 92 patients with DM from in-patient division of nephrology or endocrinology in Guangdong Province's People Hospital from July 1,2014 to July 1,2017.82 patients were diagnosed as DKD and 10 were DM without kidney injury.All patients were examined by BOLD and IVIM,then MRI and clinical data were collected.Followed up until December 31,2018.The primary end points were defined as estimated GFR<15mlumin per 1.73m2,Over a 30%increase in serum creatinine or death.A low variability method called twelve-layer concentric objects(TLCO)was used to quantify the MRI values.The differences of MRI and clinical data between DKD and DM groups were compared,and the correlations between MRI and renal function were analyzed.Multivariate regression analysis was carried out to assess the risk factors.Selected the appropriate MRI values and compared outcome differences based on the interquartile ranges(IQR)of them,then compared their diagnostic efficacy with the area under the curve(AUC).RESULTSOur results showed that the R2*of DKD group was higher than that of DM group,but the D value was lower than DM group.R2*displayed a significantly negative correlation with glomerular filtration rate(GFR)(P<0.05),but D showed a significantly positive correlation with GFR(P<0.05).Results of multivariable regression analysis indicated that in age-and sex-adjusted models,the renal adverse event correlated positively with baseline eGFR(regression coefficient ?:0.94,95%confidence interval[95%CI]:0.92-0.97,P = 0.001),hemoglobin(Hb)(?:0.95,[95%CI]:0.92-0.98,P=0.004),CR2*(?:1.19,[95%CI]:1.02-1.40,P=0.026),MR2*(?:1.14,[95%CI]:0.99-1.31,P = 0.045),and CD(?:0.89,[95%CI]:0.81-0.98,P =0.020),but other mentioned covariates.The higher MR2*(log-rank,P = 0.000)or the lower CD(log-rank,P = 0.000)predicted a worse renal outcome among the groups of them and the corresponding areas under the curve(AUC)were 0.80(95%CI:0.69-0.89)and 0.23(95%CI:0.11-0.36)respectively.Importantly,combination of MR2*and CD exhibited a significant prognosis diversity(log-rank,P = 0.000),meanwhile,a markedly increased AUC(0.85,95%CI:0.74-0.95)than anyone of them was proven.CONCLUSIONIn summary,our results demonstrate that the fMRI values corresponded to hypoxemia and fibrosis in kidney and correlates with the decline of renal function.The two indicators are sensitive in prognostic difference in patients with DKD.Importantly,integrating BOLD-MRI and IVIM-DWI is better than single one,therefor,it can be a multilateral,repeatable and noninvasive tool to predict the outcomes of DKD.