© 2018, Sociedade Brasileira para o Desenvolvimento de Pesquisa em Cirurgia. All rights reserved.Purpose: To evaluate the clinical stenosis or precursor histological changes that ureteral access sheaths commonly used in ureteroscopic surgeries may cause in the long term in ureter. Methods: In this study, the animals were divided into 9 groups and according to their groups, ureters of the rabbits were endoscopically fitted with 2F and 3F ureter catheters. The catheters were left in place and withdrawn after a specified period of time. All the ureters were excised and evaluated macroscopically, microscopically and histologically. Ureter diameters were measured and FGF-2 (+) labeled fibroblasts were counted in connective tissue as stenosis precursors. Results: Macroscopically or microscopically, no stenosis was found in any group. The ureter diameter of the group that were catheterized for the longest time with the catheter that had the widest diameter was significantly lower than the group with the shorter duration and the catheter with the narrower diameter and the control group. When the groups were compared in terms of their FGF values, there was a significant difference in FGF-2 counts at all three ureter levels (p <0.05). Conclusion: The use of ureteral access sheath may lead to histological changes, as its diameter and duration increase.