Role of Diffusion Tensor Imaging in renal parenchymal changes

Diffusion Tensor Imaging (DTI) is a reliable noninvasive tool to assess renal function with medullary Fractional Anisotropy (FA) values showing the most consistent results.

Evaluation of FA, Apparent Diffusion Coefficient (ADC) for detecting diabetic nephropathy (DN) using 1.5-Tesla magnetic resonance imaging (MRI). To determine FA and ADC values in chronic kidney disease (CKD) patients and controls, and comparing these with estimated glomerular filtiration rate (eGFR) and categorizing the stage of CKD.

Thirty nondiabetic volunteers underwent DTI. The study included 83 diabetics, 30 frank urine proteinuric, 30 micro-albuminuric, 23 normo-albuminuric with only raised blood sugar patients. Patients were stratified by eGFR into groups: eGFR <60 and eGFR>60ml/min. ADC and FA values in cortex and medulla were compared between controls and study groups.

Analysis of variance and Pearson correlation using SPSS 16 were performed.

There was significant difference of FA medulla in controls versus albuminuric and micro-albuminuric versus frank proteinuric patients (P < 0.001). Also, there was significant difference between cortical ADC values between normal, microalbuminuric/proteinuric groups (P = 0.010, P =0.000, respectively). Significant difference between medullary FA values of patients with eGFR >60 and eGFR < 60 versus normal controls (P < 0.001) was noted. With declining renal function from normal to CKD category 5, a negative correlation between medullary FA (r= -0.785, P = 0.001) and ADC cortex values (r= -0.436, P = 0.001) was noted. A strong positive correlation between medullary FA and cortex ADC with eGFR (r = 0.598 and 0.344, respectively) was noted.

Medullary FA of diabetics with relatively intact kidney function were significantly lower than those of controls. Hence, drop in medullary FA values can be an indicator of early nephropathy/patients at risk where eGFR is in near normal range. Cortical ADC and medullary FA demonstrated a significant correlation with eGFR with the latter showing a stronger positive correlation.