title: Coated v noncoated ureteral metal stents: an experimental model.
abstract: OBJECTIVE
  The purpose of the present study was to compare the standard metal stents with internally and externally coated metal stents in the pig model.
  
  
  METHODS
  In nine female pigs weighing between 25 and 30 kg, the metal stents were randomly placed in either the right or left ureter, for a total of 18 stented ureters. Six ureters were stented with a Wallstent (Schneider, Zurich, Switzerland), six with a Passager stent (Boston Scientific, Natick, MA, USA), and six with a Corvita endoluminal graft (CEG) (Boston Scientific, Natick, MA, USA). Patency was examined by nephrostotomography 24 hours and 21 days after the initial procedure.
  
  
  RESULTS
  Free flow of urine through the stents into the bladder was revealed in all ureters with the exemption of four cases where a Passager stent migrated into the bladder, jeopardizing ureteral patency. The Wallstent generated mild inflammation with metaplasia of the urothelium; the CEG a more pronounced inflammatory response in the adjacent ureter; and the Passager stent severe inflammatory reaction with necrosis of the urothelium. The sections of the Wallstents revealed the presence of a mild polypoid reaction adherent to the internal surface of the devices. The coated stents showed no tissue ingrowth through the lining material into the ureteral lumen, and thus, the urothelium was compressed beneath the prostheses.
  
  
  CONCLUSIONS
  Our experimental results suggest that the standard Wallstent generates less inflammation of the surrounding tissues than coated stents. The coated stents have the advantage of minimal tissue ingrowth but have a tendency to migrate toward the bladder.
authors.affiliation: Department of Urology, University of Patras, School of Medicine, Greece.
authors.forename: E N
authors.initials: EN
authors.lastname: Liatsikos
authors.forename: D
authors.initials: D
authors.lastname: Siablis
authors.forename: C
authors.initials: C
authors.lastname: Kalogeropoulou
authors.forename: D
authors.initials: D
authors.lastname: Karnabatidis
authors.forename: A
authors.initials: A
authors.lastname: Triadopoulos
authors.forename: L
authors.initials: L
authors.lastname: Varaki
authors.forename: P
authors.initials: P
authors.lastname: Zabakis
authors.forename: P
authors.initials: P
authors.lastname: Perimenis
authors.forename: G A
authors.initials: GA
authors.lastname: Barbalias
mesh_terms: D000818:Animals; D020099:Coated Materials, Biocompatible; D005260:Female; D005548:Foreign-Body Migration; D007249:Inflammation; D023421:Models, Animal; D009336:Necrosis; D015607:Stents; D013552:Swine; D014513:Ureter / Q000473:pathology / Q000601:surgery*; D014517:Ureteral Obstruction / Q000276:immunology / Q000473:pathology / Q000601:surgery*; D001743:Urinary Bladder; D019459:Urothelium / Q000473:pathology / Q000601:surgery
chemical_list: D020099:Coated Materials, Biocompatible