Objective To observe the in vivo degradation of poly-DL-lactic acid ureteral stent in canine and the pathological change in canine ureter.Methods Poly-DL-lactic acid ureteral stent was inserted into 19 canine ureters,respectively.The stents were taken out every two weeks with their degradation observed with electronic microscopy and their molecular weight change detected by gel permeation chromatography.Pathological change in ureteral tissue specimens stained with hematoxylin and eosin was observed by light microscopy.Results The molecular weight of poly-DL-lactic acid ureteral stent was decreased to 8 033 seven weeks after degradation from 68 900 before degradation,with a degradation rate of 88.3%.Electronic microscopy showed that the number of pores in stent was gradually increased and their diameter became larger.The stent was degraded.The main pathological change observed in canine ureter tissue was non-specific inflammation.Conclusion Poly-DL-lactic acid ureteral stent is good in degradation property and tissue compatibility in vivo.