Comparative performance of uncoated, self-expanding metal biliary stents of different designs in 2 diameters: final results of an international multicenter, randomized, controlled trial

Gastrointest Endosc. 2009 Sep;70(3):445-53. doi: 10.1016/j.gie.2008.11.018. Epub 2009 May 30.


Background: The Wallstent has remained the industry standard for biliary self-expanding metal stents (SEMSs). Recently, stents of differing designs, compositions, and diameters have been developed.

Objective: To compare the new nitinol 6-mm and 10-mm Zilver stents with the 10-mm stainless steel Wallstent and determine the mechanism of obstruction.

Design: Randomized, prospective, controlled study.

Setting: Nine centers experienced in SEMS placement during ERCP.

Patients: A total of 241 patients presenting between September 2003 and December 2005 with unresectable malignant biliary strictures at least 2 cm distal to the bifurcation.

Main outcome measurement: Stent occlusions requiring reintervention and death.

Results: At interim analysis, a significant increase in occlusions was noted in the 6-mm Zilver group at the P = .04 level, resulting in arm closure but continued follow-up. Final study arms were 64, 88, and 89 patients receiving a 6-mm Zilver, 10-mm Zilver, and 10-mm Wallstent, respectively. Stent occlusions occurred in 25 (39.1%) of the patients in the 6-mm Zilver arm, 21 (23.9%) of the patients in the 10-mm Zilver arm, and 19 (21.4%) of the patients in the 10-mm Wallstent arm (P = .02). The mean number of days of stent patency were 142.9, 185.8, and 186.7, respectively (P = .057). No differences were noted in secondary endpoints, and the study was ended at the 95% censored study endpoints. Biopsy specimens of ingrowth occlusive tissue revealed that 56% were caused by benign epithelial hyperplasia.

Conclusions: SEMS occlusions were much more frequent with a 6-mm diameter SEMS and equivalent in the two 10-mm arms despite major differences in stent design, material, and expansion, suggesting that diameter is the critical feature. Malignant tumor ingrowth produced only a minority of the documented occlusions.

Publication types

  • Comparative Study
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Alloys
  • Bile Duct Neoplasms / complications
  • Bile Duct Neoplasms / pathology
  • Catheterization / methods*
  • Cholangiopancreatography, Endoscopic Retrograde / methods
  • Cholestasis / etiology
  • Cholestasis / mortality
  • Cholestasis / pathology*
  • Cholestasis / therapy*
  • Female
  • Humans
  • International Cooperation
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Neoplasm Staging
  • Palliative Care / methods*
  • Patient Selection
  • Probability
  • Prognosis
  • Prospective Studies
  • Prosthesis Design
  • Prosthesis Failure
  • Quality of Life
  • Risk Assessment
  • Stainless Steel
  • Stents*
  • Survival Analysis
  • Terminally Ill
  • Treatment Outcome


  • Alloys
  • Stainless Steel
  • nitinol