title: Spiral nitinol biliary stents in a porcine model: evaluation of the potential for use in benign strictures.
abstract: OBJECTIVE
  Self-expanding spiral nitinol stents are potentially removable and may be useful in the treatment of benign strictures. We evaluated the histologic response to stent placement and technical aspects of their placement and removal in a porcine model.
  
  
  METHODS
  Nine animals were studied. Stents were placed above the papilla in six surviving animals. After intervals of one, two or three months cholangiography and attempted stent removal was performed. Four animals were then sacrificed acutely with their stent in place, and two were sacrificed after a one-month healing interval. The results of placement, follow-up cholangiography and histology are reported.
  
  
  RESULTS
  Cholangiography and stent placement succeeded in 26 of 27 and 11 of 16 attempts, respectively. Three placement failures were attributed to stent/duct size disparity or a faulty release mechanism, resulting in stent kinking and/or duct twisting. Among the successfully deployed stents, two animals developed strictures where stents traversed bifurcations and one exhibited partial luminal compromise by tissue entrapment between coils. Fluoroscopically guided removal was successful in two of five stents positioned above the papilla. Histology was non-specific but minimally changed in those given a one-month healing interval after removal. Others exhibited moderate inflammation, fibrosis and an intramural abscess at sites of induced stricture.
  
  
  CONCLUSIONS
  Spiral metal stents for the treatment of benign strictures remain experimental. Care must be taken to deploy them in bile ducts of adequate diameter and endoscopic removal is not yet demonstrably reliable and safe.
authors.affiliation: Division of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Van Os
authors.forename: B T
authors.initials: BT
authors.lastname: Petersen
authors.forename: K P
authors.initials: KP
authors.lastname: Batts
mesh_terms: D000497:Alloys; D000818:Animals; D001652:Bile Ducts / Q000473:pathology*; D001660:Biliary Tract Diseases / Q000628:therapy*; D002758:Cholangiography; D003251:Constriction, Pathologic; D004195:Disease Models, Animal; D005069:Evaluation Studies as Topic; D011474:Prosthesis Design; D015607:Stents; D013552:Swine
chemical_list: D000497:Alloys; C013616:nitinol