BACKGROUND Ureteral endoprostheses are used for dilatation of strictures in order to maintain upper urinary tract (UUT) function for a longer period. METHODS Three kinds of short (3-4-cm) endoprostheses were inserted into the ureter of mongrel dogs with intact UUT or experimental ureter strictures. The UUT function was evaluated by means of radiographic examinations and in terms of following measures of contractility: intraluminal pressure, electroureterography (EUG), and multichannel impedance ureterography (MIUG). Studies were performed 1, 3 to 6 months, and 1 to 3 years after prostheses implantation. RESULTS Similar urodynamic changes were registered in prosthetically treated ureters of dogs with initially intact UUTs and those with ureteral strictures. These disorders consisted of increased UUT intraluminal pressure and different functioning of the upper and lower regions of the ureter. The bioelectric and contractile activity of the upper UUT regions was reinforced, accelerated, and dysrhythmic, while peristaltic ureter wall function below the endoprosthesis was rare and weak. CONCLUSIONS The changes observed are typical for ureteral prosthetics. The UUT urodynamic alterations could be attributable entirely to the excluding of the ureteral segment from active contraction and were the result of the local absence of the ureteral wall closing mechanism. One must keep in mind that UUT endoprostheses produce a high load on the ureter wall. The transition from UUT hyperfunction to contractile function decompensation may depend on the intrinsic compensatory reserves of the ureter.