title: Flared polyurethane-covered self-expandable nitinol stent for malignant biliary obstruction.
abstract: OBJECTIVE
  To determine the technical efficacy and safety of a flared polyurethane-covered self-expandable nitinol stent in the management of malignant biliary obstruction and to evaluate its clinical efficacy by estimating stent patency and patient survival rates.
  
  
  METHODS
  Thirteen patients with common bile duct strictures (nonhilar) caused by malignant disease were treated by placement of 13 nitinol stents. The stents used include a flared section in the proximal portion (12 mm in diameter and 10 mm in length) and a section in the remnant portion that is fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of 50-80 mm. Patient survival and stent patency rates were calculated with use of Kaplan-Meier survival analysis. The follow-up bilirubin and serum amylase and lipase levels were calculated, and the differences in means were evaluated with use of a Wilcoxon signed-rank test. The average follow-up duration was 22.9 weeks (range, 8-56 weeks).
  
  
  RESULTS
  Placement was successful in all cases. The 30-day mortality rate was 0%. The survival rates were 38% and 24% at 20 and 50 weeks, respectively. Seventy-seven percent of study patients had adequate palliative drainage during their the remainder of their lives. The stent patency rates were 71% and 48% at 20 and 50 weeks, respectively. Three patients (23%) presented with stent occlusion requiring repeat intervention. There were no procedure-related complications such as proximal or distal migration. No complications occurred other than stent occlusion. One patient's stent was removed under endoscopic guidance 15 weeks after its insertion. Bilirubin levels had significantly decreased 1 week after stent insertion (P <.001).
  
  
  CONCLUSIONS
  Preliminary results suggest that placement of a flared polyurethane-covered self-expandable nitinol stent is feasible and effective in achieving biliary drainage. The stents do not migrate, but there is tumor ingrowth into the flared portion of the stent. Treatment of a larger group of patients will be mandatory to validate these long-term results.
authors.affiliation: Department of Radiology, Chonbuk National University Medical School, 634-18, Keumam-Dong, Chonju, 560-182, South Korea. ymhan@chonbuk.ac.kr
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Han
authors.forename: Gong-Yong
authors.initials: GY
authors.lastname: Jin
authors.forename: Seung-Ok
authors.initials: SO
authors.lastname: Lee
authors.forename: Hyo-Sung
authors.initials: HS
authors.lastname: Kwak
authors.forename: Gyung-Ho
authors.initials: GH
authors.lastname: Chung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000497:Alloys; D001651:Cholestasis, Extrahepatic / Q000000981:diagnostic imaging / Q000209:etiology / Q000628:therapy*; D020099:Coated Materials, Biocompatible; D003137:Common Bile Duct Diseases / Q000000981:diagnostic imaging / Q000209:etiology / Q000628:therapy*; D004867:Equipment Design; D004868:Equipment Failure; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000150:complications; D006801:Humans; D008297:Male; D008875:Middle Aged; D011140:Polyurethanes; D011859:Radiography; D015607:Stents / Q000009:adverse effects; D015996:Survival Rate
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D011140:Polyurethanes; C013616:nitinol