title: New antireflux self-expandable metal stent for malignant lower biliary obstruction: in vitro and in vivo preliminary study.
abstract: OBJECTIVE
  Antireflux plastic biliary stents prevent duodenal biliary reflux and improve the stent patency rate. However, the efficacy of the antireflux valve in a self-expandable metal stent (SEMS) for a malignant biliary obstruction has not been well established. We evaluated the efficacy of a SEMS with an antireflux valve using in vitro flow studies and determined the impact of reducing duodenobiliary reflux on the stent patency rate.
  
  
  METHODS
  In vitro testing was conducted using a bile perfusion system to evaluate the antegrade and retrograde flow resistance, and to determine the ideal shape for the valve. Then, a prospective case series in humans was conducted with an adequately designed SEMS with an antireflux valve.
  
  
  RESULTS
  During the study period, five patients with an unresectable non-hilar malignant biliary obstruction underwent insertion of a SEMS with an antireflux valve. Placement of the SEMS with antireflux valve was successful on the first attempt in all patients, and no procedure-related complications occurred. Follow up was obtained in all cases. Serum bilirubin level did not decrease to the normal range within 1 month in four patients. Stent occlusions occurred in all four patients as a result of valve malfunctions due to sludge impaction or a clog. Therefore, the study was terminated early due to unexpected results.
  
  
  CONCLUSIONS
  SEMS with an antireflux valve was ineffective in patients with non-hilar malignant biliary obstruction due to limitations on current stent technology.
authors.affiliation: Department of Internal Medicine, Pusan National University School of Medicine and Biomedical Research Institute, Yangsan-si, Korea.
authors.forename: Dong Uk
authors.initials: DU
authors.lastname: Kim
authors.forename: Chang-Il
authors.initials: CI
authors.lastname: Kwon
authors.forename: Dae Hwan
authors.initials: DH
authors.lastname: Kang
authors.forename: Kwang Hyun
authors.initials: KH
authors.lastname: Ko
authors.forename: Sung Pyo
authors.initials: SP
authors.lastname: Hong
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001650:Bile Duct Neoplasms / Q000601:surgery*; D001655:Bile Reflux / Q000601:surgery*; D002779:Cholestasis / Q000601:surgery*; D004867:Equipment Design; D004868:Equipment Failure; D005240:Feasibility Studies; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008670:Metals; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D015607:Stents; D016896:Treatment Outcome
chemical_list: D008670:Metals