title: Membrane degradation of covered stents in the upper gastrointestinal tract: frequency and clinical significance.
abstract: OBJECTIVE
  To evaluate the frequency, clinical significance, and predictive factors of membrane degradation of covered stents in the upper gastrointestinal (UGI) tract.
  
  
  METHODS
  From 1996 to 2006, 166 stents were removed from 151 patients. Indications for stent removal included temporary stent placement for esophageal cancer before radiation therapy or radiation-chemotherapy (n = 53), stent migration (n = 40), temporary stent placement for a benign UGI stricture (n = 32), pain (n = 21), recurrent obstruction (n = 16), incomplete stent expansion (n = 1), recurrent transesophageal fistula (n = 2), and aspiration (n = 1). Removed stents were examined to evaluate possible causes of membrane degradation. Multivariate analysis was performed to determine the predictive factors of membrane degradation.
  
  
  RESULTS
  Degradation of the covering membrane occurred in 14 of the 166 stents (8%). Recurrent obstruction due to tumor ingrowth (n = 7) and reopening of the transesophageal fistula (n = 1) through the degraded membrane occurred in eight stents (5%). At multivariate logistic regression analysis, the type of covering membrane (P = .018), stricture location (P = .006), and duration of stent placement (P = .002) were significantly associated with degradation of the covering membrane.
  
  
  CONCLUSIONS
  Degradation of the covering membrane after stent placement in the UGI tract is not an uncommon event, and recurrent obstruction or fistula can occur through the degraded membrane. A polyurethane membrane is not biostable and dissolves over time, particularly in the gastroduodenal area.
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap-2dong, Songpa-gu, Seoul 138-736, Republic of Korea.
authors.forename: Jin Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Ho-Young
authors.initials: HY
authors.lastname: Song
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Shin
authors.forename: Hwoon-Yong
authors.initials: HY
authors.lastname: Jung
authors.forename: Sung-Bae
authors.initials: SB
authors.lastname: Kim
authors.forename: Jong-Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Seung-Il
authors.initials: SI
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000497:Alloys; D003251:Constriction, Pathologic; D020878:Device Removal; D005260:Female; D005767:Gastrointestinal Diseases / Q000473:pathology / Q000628:therapy*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011138:Polytetrafluoroethylene; D011446:Prospective Studies; D011475:Prosthesis Failure; D015607:Stents; D041742:Upper Gastrointestinal Tract
chemical_list: D000497:Alloys; C013616:nitinol; D011138:Polytetrafluoroethylene