Use of diffusion tensor MRI to identify early changes in diabetic nephropathy

Abstract

Background/aims: Currently available clinical indicators of kidney disease lack the sensitivity and/or specificity to identify early-stage diabetic nephropathy (DN). Quantitative diffusion magnetic resonance imaging (MRI), specifically diffusion tensor imaging (DTI), has been used to quantify pathophysiologic changes in other organs but has not been well studied in kidney diseases, including DN. The goal of this pilot study was to examine differences in kidney DTI parameters in diabetic subjects versus healthy controls.

Methods: 16 diabetic and 5 healthy control subjects were recruited for this institutional review board-approved/Health Insurance Portability and Accountability Act-compliant study. Kidneys were scanned using DTI to generate apparent diffusion coefficient (ADC) and fractional anisotropy (FA) data. Mean cortical and medullary ADC and FA values were calculated by selecting multiple regions of interest. Diabetics were stratified by estimated glomerular filtration rate (eGFR) into 2 groups: eGFR ≥60 (n = 10) and eGFR <60 (n = 6) ml/min/1.73 m(2). Mean diffusion parameters and eGFRs were compared between these groups of diabetic subjects and healthy controls.

Results: Medullary FA, ADC and cortical ADC values were significantly lower in diabetics with eGFR <60 compared to controls. Notably, both mean medullary FA and ADC were significantly lower in diabetics with eGFR ≥60 compared to controls (p = 0.001 and p = 0.042, respectively). For the study subjects in aggregate, medullary FA correlated significantly with eGFR (R = 0.69, p < 0.01); the other diffusion parameters showed no significant correlations.

Conclusions: This pilot study suggests that changes in medullary DTI assessments may serve as indicators of early DN. Further studies are needed to determine if these findings could serve as biomarkers to identify diabetics at risk of DN progression.

Fig. 1

a Coronal T2-weighted MRI images of a control kidney. b Representative cortical and medullary ROIs are overlaid onto representative T2-weighted HASTE images.

Fig. 2

Comparisons of diffusion MRI parameters in a healthy control and in diabetics with different levels of estimated renal function. Imaging data (ADC and FA diffusion maps) are shown for a healthy control subject (first panel), 2 diabetic subjects with normal eGFRs (2nd and 3rd panel) and a diabetic subject with more advanced disease (4th panel). Medullary FA for 1 of the diabetic subjects with a normal eGFR is similar to that of the healthy control, with prominent areas of high FA evident. In contrast, medullary FA is decreased for the other diabetic with a normal eGFR as well as the diabetic subject with advanced CKD.

Fig. 3

Medullary FA and eGFR in diabetic and normal subjects. The dot plot shows medullary FA plotted as a function of eGFR for both diabetic (•) and control subjects (▵). A highly significant Pearson correlation (r = 0.69, p < 0.01) was observed between medullary FA and eGFR. Correlations between the other imaging parameters (cortical FA, medullary ADC and cortical ADC) and eGFR were not significant.