title: Risk factors for technical failure of endoscopic double self-expandable metallic stent placement by partial stent-in-stent method.
abstract: BACKGROUND
  Endoscopic double self-expandable metallic stent (SEMS) placement by the partial stent-in-stent (PSIS) method has been reported to be useful for the management of unresectable hilar malignant biliary obstruction. However, it is technically challenging, and the optimal SEMS for the procedure remains unknown. The aim of this study was to identify the risk factors for technical failure of endoscopic double SEMS placement for unresectable malignant hilar biliary obstruction (MHBO).
  
  
  METHODS
  Between December 2009 and May 2013, 50 consecutive patients with MHBO underwent endoscopic double SEMS placement by the PSIS method. We retrospectively evaluated the rate of successful double SEMS placement and identified the risk factors for technical failure.
  
  
  RESULTS
  The technical success rate for double SEMS placement was 82.0% (95% confidence interval [CI]: 69.2-90.2). On univariate analysis, the rate of technical failure was high in patients with metastatic disease and unilateral placement. Multivariate analysis revealed that metastatic disease was a significant risk factor for technical failure (odds ratio: 9.63, 95% CI: 1.11-105.5). The subgroup analysis after double guidewire insertion showed that the rate of technical success was higher in the laser-cut type SEMS with a large mesh and thick delivery system than in the braided type SEMS with a small mesh and thick delivery system.
  
  
  CONCLUSIONS
  Metastatic disease was a significant risk factor for technical failure of double SEMS placement for unresectable MHBO. The laser-cut type SEMS with a large mesh and thin delivery system might be preferable for the PSIS procedure.
authors.affiliation: Department of Gastroenterology and Hepatology, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Kazumichi
authors.initials: K
authors.lastname: Kawakubo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawakami
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Toyokawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Otani
authors.forename: Masaki
authors.initials: M
authors.lastname: Kuwatani
authors.forename: Yoko
authors.initials: Y
authors.lastname: Abe
authors.forename: Shuhei
authors.initials: S
authors.lastname: Kawahata
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Kubo
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Kubota
authors.forename: Naoya
authors.initials: N
authors.lastname: Sakamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002779:Cholestasis / Q000601:surgery*; D004067:Digestive System Neoplasms / Q000601:surgery*; D016145:Endoscopy, Digestive System / Q000379:methods*; D004868:Equipment Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D015607:Stents
keywords: Endoscopic biliary drainage; Malignant hilar biliary obstruction; Self-expandable metallic stent; Stent-in-stent method