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 3.0 T SWI using a 2D gradient-echo sequence.

Assessment: The relative SWI signal ratio(r) of cortical and medulla (r = SI /SI ) 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  = 0.91, 0.81, respectively).

Data Conclusion: The SWI sequence could provide a quantitative evaluation of renal fibrosis during UUO progression.

Level Of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1572-1577.