title: Self-expanding polytetrafluoroethylene covered nitinol stents for the treatment of ureteral stenosis: preliminary report.
abstract: OBJECTIVE
  We evaluated the treatment of ureteral stenosis using a self-expanding nitinol stent covered with expanded polytetrafluoroethylene (ePTFE).
  
  
  METHODS
  Between January 2001 and April 2003, 37 ePTFE covered metal stents were implanted in 20 patients with a total of 29 ureteral stenoses due to various causes. In general the stents were introduced by using a retrograde approach under combined endoscopic and fluoroscopic guidance with patients under spinal block and sedation. Followup assessments in 18 patients, including urography, were done 3, 6, 12, 18 and 24 months after the procedure. Followup endoscopic examinations were performed at 6 and 12 months in 8 patients.
  
  
  RESULTS
  Immediate ureteral patency was achieved during all insertion procedures and maintained in most patients. Four patients died of the neoplastic process 3 to 12 months after implantation. Four stent migrations occurred in 3 patients (22.2%), which was resolved by implanting a new stent. Nonobstructive mucous hyperplasia was observed in 5 patients (27.7%) at the end of the stent, although there was no internal calcification. In all cases the stents remained patent until the current time or until patient death.
  
  
  CONCLUSIONS
  We found that ePTFE covered nitinol stents were safe and effective for ureteral stenosis. Their resistance to calcification was high with nonobstructive hyperplasia developing in only a few cases and only at the stent ends. The ideal material for covering stents would produce no mucous hyperplasia.
authors.affiliation: Diagnostic Radiology Services, Hospital Clínico Universitario, Valladolid, Spain. FJTRUEBA@USUARIOS.RETECAL.ES
authors.forename: F J
authors.initials: FJ
authors.lastname: Trueba Arguiñarena
authors.forename: E
authors.initials: E
authors.lastname: Fernández del Busto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000497:Alloys; D003251:Constriction, Pathologic; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011138:Polytetrafluoroethylene; D015607:Stents; D014513:Ureter / Q000473:pathology*
chemical_list: D000497:Alloys; C013616:nitinol; D011138:Polytetrafluoroethylene