Reimplantation of the ureter after unilateral ureteral obstruction provides a model that allows functional evaluation

Experimental unilateral ureteral obstruction (UUO) is widely used to study renal fibrosis; however, renal injury can only be scored semiobjectively by histology. We sought to improve the UUO model by reimplanting the obstructed ureter followed by removal of the contralateral kidney, thus allowing longitudinal measurements of renal function. Mice underwent UUO for different lengths of time before ureteral reimplantation and contralateral nephrectomy. Measurement of blood urea nitrogen (BUN) allows objective evaluation of residual renal function. Seven weeks after reimplantation and contralateral nephrectomy, mean BUN levels were increased with longer duration of UUO. Interstitial expansion, fibrosis, and T-cell and macrophage infiltration were similar in kidneys harvested after 10 days of UUO or following 10 weeks of ureter reimplantation, suggesting that the inflammatory process persisted despite relief of obstruction. Urinary protein excretion after reimplantation was significantly increased compared to control animals. Our study shows that functional assessment of the formerly obstructed kidney can be made after reimplantation and may provide a useful model to test therapeutic strategies for reversing renal fibrosis and preserving or restoring renal function.