Ureteral response to the placement of metallic stents: an animal model

Metallic self-expanding mesh stents are increasingly used in the urinary tract. Little is known about the histological reactions that such prostheses have on the surrounding tissue. The effects of self-expanded metallic stents in the histologically normal ureter were examined in four dogs. Three-mm. Gianturco-Roubin coronary artery stents were introduced into the distal left ureter after dilatation. Follow-up excretory urography, retrograde pyelograms and autopsy were performed on 2 dogs at 1 month and on 2 dogs at 6 months. In all 4 dogs, the ureters remained patent. Histologic examination of the ureter showed that the stents had not become incorporated within the wall of the ureter. Reactive changes seen in the epithelium included penetration of both epithelium and submucosa between the wire struts and areas of fibrosis in the submucosal layer. The use of metallic stents in histologically normal ureters may be limited in the long term by this inflammatory response.