Longitudinal Assessment of Rabbit Renal Fibrosis Induced by Unilateral Ureteral Obstruction Using Two-Dimensional Susceptibility Weighted Imaging

Background: Previous studies indicated that two-dimensional-susceptibility weighted imaging (2D-SWI) could serve as a useful biomarker for differentiating the grade of liver fibrosis. Purpose: To evaluate the feasibility of 2D-SWI in the dynamic quantification of renal fibrosis in a rabbit model. Study type: Longitudinal study. Animal model: Twenty-Four New Zealand White Rabbits including control group (n=4); and renal fibrosis group (n=20), by means of a unilateral ureteral obstruction (UUO) model. Field Strength/Sequence: The 3.0T SWI using a 2D gradient-echo sequence. Assessment: The relative SWI signal ratio(r) of cortical and medulla (r=SIrenal/SImuscle) was longitudinally assessed before ligation and on weeks 2, 4, 6, and 8 following ligation. Sirius Red staining was used to assess the degree of fibrosis in five high-power fields. Statistical tests: The repeated measures of analysis of variance and linear regression analysis. Results: Both the cortical and medullary r values were significantly higher in the UUO kidneys at week 2 compared with the kidneys before ligation. Over the course of UUO progression, significant changes occurred in the cortical and medullary r values in vivo and fibrosis scores in vitro (all P values<0.05). The r values gradually decreased, while the fibrosis scores gradually increased over 8 weeks following ligation. The linear regression analysis showed a strong and significant correlation between cortical and medullary r values and the pathologic fibrosis scores (R-2=0.91, 0.81, respectively). Data conclusion: The SWI sequence could provide a quantitative evaluation of renal fibrosis during UUO progression. Technical Efficacy: Stage 1