应用功能磁共振成像判断急性肾损伤患者肾脏慢性病变及预测肾功能转归

Functional magnetic resonance imaging to evaluate the nature of kidney lesions and predict the outcome of renal function in acute kidney injury

目的:探索功能磁共振(fMRI)在评估急性肾损伤(AKI)患者是否存在慢性基础肾脏病变及肾功能预后转归中的价值。方法:回顾性分析国家肾脏疾病临床医学研究中心诊断为AKI并同时行fMRI检查及肾活检的13例患者资料。收集患者常规病理数据(包括免疫荧光、光镜、电镜)以及病理诊断,统计患者fMRI中体素内不相干运动成像的标准表观弥散系数参数值(IVIM Standard-ADC)和磁共振弹性成像(MRE)的弹性参数值,估算的肾小球滤过率(eGFR)在基线和12月内的随访数据,分析IVIM Standard-ADC和弹性参数值与随访期间eGFR变化斜率之间的关系。结果:13例AKI患者中男性8例、女性5例,中位年龄33(21~44)岁。平均基线eGFR为31(16.5~43.5)mL/(min·1.73 m^(2)),随访中平均年eGFR变化斜率为12.29(4.42~25.66)。经肾活检病理证实,7例存在基础慢性病变,6例为单纯AKI。12月随访中eGFR变化斜率与IVIM Standard-ADC及45 Hz条件下的弹性值均无明显相关关系,但与60 Hz条件下的弹性值呈显著正相关(rs=0.709,P=0.022),进一步将两者作回归分析可得出60 Hz条件下的弹性值可作为随访12月eGFR变化斜率的预测因素(r^(2)=0.456,P=0.032)。45 Hz条件下的弹性值也得到同样类似的结果,可作为随访12月eGFR变化斜率的预测因素(r^(2)=0.440,P=0.036)。即MRE可相对区分肾脏损伤程度及不同的eGFR恢复斜率。结论:MRE可作为一种新的方法预测AKI患者肾功能预后情况。相比于单纯AKI患者,AKI合并CKD患者的肾功能难以完全恢复正常,二者基线弹性值有显著差别。

Objective:We aimed to explore whether the functional magnetic resonance imaging(fMRI),an noninvasive technique,could judge the nature of kidney lesions and predict recovery of kidney function in acute kidney injury(AKI)patients.Methodology:13 AKI patients who underwent fMRI and renal biopsy in the National Clinical Research Center of Kidney Diseases were enrolled in this study.The routine pathological data,including immunofluorescence,light microscopy,and electron microscopy,and pathology diagnoses were collected for each patient.Apparent diffusion coefficient of intravoxel incoherent motion diffusion weighted imaging(IVIM Standard⁃ADC)and magnetic resonance elastography(MRE)⁃derived stiffness,as well as baseline estimated glomerular filtration rate(eGFR)and follow⁃up data within 12 months after discharge were recorded for each patient.The relationship between IVIM Standard⁃ADC and MRE⁃derived stiffness and the rate of eGFR change during the follow⁃up period was analyzed.Results:Of the 13 patients(8 males,5 females),the median age was 33(21~44)years.Mean baseline eGFR was 31(165~435)mL/(min·173 m^(2)),and mean annual eGFR slope was 1229(442~2566).The results of histology shows that 7 cases had chronic lesions and 6 cases were simple AKI.First,the slope of eGFR change over the 12 months follow⁃up period was not significantly correlated with the values of IVIM Standard⁃ADC and 45 Hz MRE⁃derived stiffness,but was significantly positively correlated with 60 Hz MRE⁃derived stiffness(rs=0709;P=0022).Moreover,increased kidney stiffness was associated with better prognosis in kidney function in AKI(regression r^(2)=0456;P=0032).Second,we can see the same result in 45 Hz MRE⁃derived stiffness,the value of 45 Hz MRE⁃derived stiffness also could be a predictor of annual eGFR slope(regression r^(2)=044;P=0036).That is,MRE⁃derived stiffness can relatively distinguish kidney injury degree and different eGFR recovery slope.Conclusion:The study indicates that MRE can predict the change of kidney function in the future in AKI patients as a powerful noninvasive tool.Compared with the pure AKI patients,kidney function in patients with AKI combined with CKD is difficult to completely return to normal,and the baseline MRE⁃derived stiffness of the two patients are significantly different.