Thirty-eight healthy New Zealand rabbits were randomly divided into the blank control group and the experimental group. The rabbits model was built by intravenous injection of C-bovine serum albumin (C-BSA) to rabbits of the experimental group. According to the different time points (2, 4, 6 and 8 weeks) after the injection of C-BSA, the rabbits in experimental group were randomly divided into 4 sub groups, 8 in each group. We collected the data of the CEUS parameters in the control group and the experimental group. Moreover, the renal tissues of the rabbits underwent pathologic examinations. Then, correlation analysis of CEUS parameters with parameters of renal fibrosis was performed.

Dynamic changes of CEUS parameters: Renal cortical perfusion reduced from 6 weeks after the injection, manifested as the time to peak (TTP) and mean transit time (MTT) of the experimental group were longer than those of control group and the derived peak intensity (DPI) of the experimental group was lower than that of control group (P<0.05 respectively). The DPI and TTP at 8 weeks after the injection of the experimental group was significantly lower than those of the control group [(26.96±2.34) db vs (35.04±1.62) db, P<0.05; (24.31±1.82) s vs (18.64±1.15) s, P<0.01]. Changes of each renal fibrosis parameter: we found that the results of the glomerulosclerosis indexes of the experimental group (4 weeks, 6 weeks and 8 weeks after the injection) were significantly higher than those of the control group (0.81±0.36, 1.43±0.25 and 2.15±0.30 vs 0.13±0.07, all P<0.01). The tubular interstitial collagen deposition scores of the experimental group (4 weeks, 6 weeks and 8 weeks after the injection) were significantly higher than those of the control group (14.29%±4.62%, 26.28%±10.09% and 42.37%±10.41% vs 1.21%±0.15%, all P<0.01). As the disease progressed, the results of each parameter increased. Pearson correlation analysis showed that the TTP of renal cortex was positively correlated with the glomerulosclerosis index and tubular interstitial collagen deposition score (r=0.866 and 0.785, both P<0.01). The DPI of renal cortex was negatively correlated with the glomerulosclerosis index and tubular interstitial collagen deposition score (r=-0.724 and -0.739, both P<0.01).

The results showed that CEUS could evaluate microcirculation perfusion of renal cortex. There is a positive association between TTP and fibrosis index. There is a negative association between DPI and fibrosis index. Thus, CEUS is an important method to evaluate the renal fibrosis in chronic renal nephropathy.