Ureteral obstruction and ureteral fistulas after aortofemoral or aortoiliac bypass surgery. Ureteral injury after aortofemoral or aortoiliac bypass surgery has seldom been described in the literature considering the large number of bypass operations performed. Some causative factors, such as the position of the bypass, are obvious while others are less clear. However, no attempt has been made to unify criteria to establish a management protocol. Of 154 cases of ureteral units with ectasia reviewed ureteral fistulas were present in 19. Radiological ureteral obstruction appears to precede fistula formation. Symptoms, time of diagnosis and treatment according to the predominant etiology have been discussed. Etiological (in varying degrees of importance), clinical and diagnostic criteria, together with a management and therapeutic protocol in which early and late lesions are clearly differentiated were established, while bearing in mind that not all radiological obstruction patterns correspond to true ureteral lesions. 