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Application of Diffusion Tensor Imaging in Obstructive Nephropathy

Background: Obstructive nephropathy is a common clinical disease. Objectives: To explore the value of diffusion tensor imaging (DTI) in obstructive nephropathy. Methods: Forty healthy Sprague-Dawley (SD) rats were examined in this study. Thirty-two animals underwent complete obstruction of the left ureter, while eight animals underwent a sham surgery. Magnetic resonance imaging (MRI) was performed before surgery and within different intervals after surgery. Eight rats from the experimental group and two rats from the sham group were used in each interval. Following MRI, the animals were sacrificed and sent for medical examinations. The scanning sequences included positioning, transverse T2-weighted (T2W), coronal, and coronal DTI sequences. Image postprocessing was performed after DTI to measure DTI parameters, including apparent diffusion coefficient (ADC) and fractional anisotropy (FA), and to reconstruct DTI fiber traces. One-way analysis of variance was used to compare the parameters between the cortex and medulla and between different intervals. Results: The fiber tracing showed that the obstructed renal fiber bundles were sparse and disordered. The ADC and FA values of the renal cortex, extrarenal medulla, and inner medulla decreased with prolonged hydrops and were negatively correlated with the expression of alpha-smooth muscle actin (α-SMA) and the renal tubulointerstitial lesion grade (r < 0, P < 0.001). Comparison of the cortex, extrarenal medulla, and inner medulla showed the following trends for the ADC and FA values: cortex > extrarenal medulla > inner medulla and cortex < extrarenal medulla < inner medulla, respectively. Conclusions: DTI in obstructive nephropathy not only can reflect the degree of renal interstitial fibrosis and accurately indicate the renal function, but also can provide information regarding renal blood perfusion, water metabolism, and ultrastructural changes.