A histological study of biopsy specimens in=52) was carried out. The specimens were obtained from the ileum mucous membrane which had contacted with urine in new bladders for a long time. Immunohistochemistry included an assessment of enterocyte expression of cell cycle markers — Ki-B7, Bcl2, p53. Epithelial proliferation was determined to be activated as early as 4—5 months after beginning to contact with urine. The process of alteration of proliferative activity consists of three phases: 1) activation, the proliferation index is 70—86% [during the first year), 2) stabilization at the level of 70% during the second year, and 3) recurrent increase up to 97% later on. There is a hypothesis that similar alterations are due to direct influence of intestinal epithelium on stem cells. The expression level of Bcl2, p53 remained low.