Objective To evaluated the renal hemodynamic changes in early diabetic nephropathy rats by color Doppler ultrasound and its correlation with podocyte damage.Methods Twenty male SD rats were randomly divided into 2 groups:,control group and diabetic nephropathy group.After 8 weeks,the systolic peak velocity (Vmax),diastolic minimum velocity (Vmin) and resistance index (RI) were measured by color Doppler ultrasound,the pathological changes in kidney tissues were obseved by HE staining,nephrin deposits were observed by immunofluorescence,and the nephrin mRNA expression in the renal cortex were detected by RT-PCR method.The difference of those results between two groups were compared,and the relationship between nephrin mRNA expression and index of renal hemodynamic were analysed.Results Compared with rats in control group,the Vmax and Vmin was lower among rats in diabetic nephropathy group [(16.63 ± 2.85)cm/s vs (24.16 ± 3.35)cm/s,P ＜0.001 and (5.41 ± 1.11)cm/s vs (9.87 ± 2.26) cm/s,P ＜0.001].However,the RI was higher than that of control group (0.73 ± 0.14 vs 0.57 ± 0.12,P =0.034).Bigger glomerular volume,increased mesangial matrix,increased mesangial cells,and visible focal lymphocytic or mononuclear cell infiltrated were observed in diabetic nephropathy group.The expressions of nephrin were lower in the cortex of renal in diabetic nephropathy group compared to control group (0.276 ± 0.015 vs 0.507 ± 0.024,P ＜0.001).Correlation analysis suggested nephrin mRNA expression was positively correlated with the Vmax and Vmin (r =0.931 and r =0.944,all P ＜0.001),and negatively correlated with RI (r =0.786,P ＜0.001).Conclusions Renal hemodynamic changes assessed by color Doppler ultrasound associated with podocyte damage in diabetic nephropathy rat,which is a noninvasive method of evaluation of early kidney damage.