title: An internally covered (lined) self-expanding metal esophageal stent: tissue response in a porcine model.
abstract: BACKGROUND
  Self-expandable metal stents (SEMS) palliate malignant dysphagia but may embed in tissue, produce granulation tissue, and prevent removal.
  
  
  OBJECTIVE
  Our purpose was to evaluate in a porcine model the tissue response induced by a new esophageal SEMS completely coated internally rather than externally.
  
  
  METHODS
  Eight Yucatan pigs were studied. Each animal underwent placement of 2 stents: 1 study stent and 1 control stent. SEMS were placed proximally or distally by random assignment. Follow-up endoscopy was performed 1, 2, 3, and 4 weeks after implantation. Ease of stent removal was assessed at 2 weeks and 4 weeks after placement.
  
  
  METHODS
  Animal laboratory.
  
  
  METHODS
  Endoscopic placement of study stents (Alveolus ES-STS, Alveolus, Inc, Charlotte, NC; 18 mm diameter, fully covered internally) and control stents (Ultraflex stent, Boston Scientific, Natick, Mass; microvasive, 18 mm midbody, subtotally covered externally).
  
  
  METHODS
  Extent of granulation tissue and stent-induced esophageal injury.
  
  
  RESULTS
  The tissue hyperplasia response of the study stents was endoscopically graded as mild to moderate. All study stents were endoscopically removed easily and atraumatically. Control stents produced severe granulation tissue formation with complete embedding of the uncovered stent ends; endoscopic removal was possible but resulted in trauma and endoscopically visible bleeding. Histopathologic findings revealed minimal tissue response at the ends of the study stents and severe pseudopolyps in the embedded portion of the control stent. Stent migration occurred in 7 of 8 study stents and 4 of 8 control stents.
  
  
  CONCLUSIONS
  Animal model lacks stricture.
  
  
  CONCLUSIONS
  Fully internally lined SEMS may resist tissue embedding and hyperplasia and may be removable. Human studies are needed to assess applicability to treatment of benign and malignant esophageal disease.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Todd H
authors.initials: TH
authors.lastname: Baron
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Burgart
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Pochron
mesh_terms: D000818:Animals; D016099:Endoscopy, Gastrointestinal; D004947:Esophagus / Q000473:pathology; D005260:Female; D006097:Granulation Tissue / Q000473:pathology*; D011474:Prosthesis Design; D015607:Stents / Q000009:adverse effects; D013552:Swine; D016610:Tissue Embedding