title: Fully covered self-expanding metal stents placed temporarily in the bile duct: safety profile and histologic classification in a porcine model.
abstract: BACKGROUND
  Fully covered Self-Expanding metal stents (FCSEMS) have been shown efficacious in palliating malignant biliary obstructions. There is little data analyzing mucosal response to their temporary placement in the bile duct.
  
  
  METHODS
  Ten mini pigs underwent endoscopic placement of a FCSEMS (Wallflex, Boston Scientific). FCSEMS were kept in place for three months. At the end of the 3 months, FCSEMS were removed endoscopically. Five pigs were euthanized and their bile ducts harvested. The other five were kept alive for another month post removal. A single pathologist, created a scoring system (to determine degree of inflammation, fibrosis, and epithelial injury), examined all specimens in a blinded fashion.
  
  
  RESULTS
  Four FCSEMS spontaneously migrated in the duodenum. On post mortem examination, mild mucosal thickness was noted in three bile duct specimens while superficial inflammation of the bile duct was noted in five animals. Histologic examination of the bile duct revealed focal acute inflammation in both groups. For the 5 animals euthanized immediately after stent removal, there was a tendency to have superficial mucosal erosion and fibrosis. In contrast, increased chronic inflammation was more commonly seen in the animals 1 month post stent removal, with all animals in this group showing moderate degrees of mononuclear inflammatory cell mucosal infiltrates. No severe inflammatory or fibrotic duct injury was observed in any of the study animals, with degree of injury graded as mild to moderate.
  
  
  CONCLUSIONS
  FCSEMS appear to induce minimal tissue overgrowth or fibrosis post placement. Ease of removability and no significant histologic injury are advantages noted with FCSEMS., however, further studies are needed to evaluate treating benign biliary strictures with FCSEMS in humans.
authors.affiliation: Digestive Health, University of Virginia, Charlottesville, VA, USA.
authors.forename: Mihir R
authors.initials: MR
authors.lastname: Bakhru
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Foley
authors.forename: Jeremy
authors.initials: J
authors.lastname: Gatesman
authors.forename: Timothy
authors.initials: T
authors.lastname: Schmitt
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Moskaluk
authors.forename: Michel
authors.initials: M
authors.lastname: Kahaleh
mesh_terms: D000818:Animals; D017734:Bile Ducts, Extrahepatic / Q000473:pathology / Q000601:surgery*; D002760:Cholangiopancreatography, Endoscopic Retrograde; D002761:Cholangitis / Q000209:etiology / Q000473:pathology*; D002908:Chronic Disease; D020099:Coated Materials, Biocompatible; D004378:Duodenal Diseases / Q000209:etiology / Q000473:pathology*; D005260:Female; D005355:Fibrosis / Q000209:etiology; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000209:etiology / Q000473:pathology*; D008670:Metals; D023421:Models, Animal; D009092:Mucous Membrane / Q000473:pathology; D015607:Stents / Q000009:adverse effects*; D013552:Swine; D013556:Swine, Miniature
chemical_list: D020099:Coated Materials, Biocompatible; D008670:Metals