title: No benefit of covered vs uncovered self-expandable metal stents in patients with malignant distal biliary obstruction: a meta-analysis.
abstract: OBJECTIVE
  Self-expandable metal stents (SEMS) are used in patients with malignant distal biliary obstruction; trials that compared covered and uncovered SEMS reported different results because of heterogeneous designs and patient populations. These studies compared patency of uncovered SEMS and covered SEMS, along with rates of pancreatitis, cholecystitis, cholangitis, SEMS migration, bleeding, perforation, and recurrent biliary obstruction.
  
  
  METHODS
  We performed a meta-analysis to compare the effects of covered and uncovered SEMS in patients with malignant distal biliary obstruction. We identified randomized controlled trials by using a literature search from 1980 through March 2012. We evaluated data from 5 full articles and 4 abstracts, comprising 1061 patients, and assessed statistical heterogeneity and publication bias.
  
  
  RESULTS
  The weighted mean difference in the stent patency duration could only be calculated on the basis of 2 studies, but it was 67.9 days longer for covered SEMS than for uncovered SEMS (95% confidence interval [CI], 60.3-75.5). A summary analysis of data from 4 trials demonstrated no differences in patency of covered vs uncovered SEMS after 6 months (odds ratio [OR], 1.82; 95% CI, 0.62-5.25) or 12 months (OR, 1.25; 95% CI, 0.65-2.39). There were also no differences in the rates of pancreatitis, cholecystitis, perforation, bleeding, or cholangitis; length of hospital stay; or number of recurrent biliary obstructions. However, covered SEMS had a higher migration rate (OR, 7.13; 95% CI, 2.29-22.21). Patients with covered SEMS had a lower rate of tumor ingrowth (OR, 0.19; 95% CI, 0.07-0.55) but a higher rate of tumor overgrowth (OR, 1.88; 95% CI, 1.02-3.45). No summary calculations could be completed to confidently assess patient survival.
  
  
  CONCLUSIONS
  The use of covered SEMS, compared with uncovered SEMS, in patients with distal malignant biliary obstruction is of unclear benefit; covered SEMS have a higher rate of migration and do not appear to have longer patency.
authors.affiliation: Division of Gastroenterology, McGill University Health Centre, Montreal General Hospital, McGill University, Montreal, QC, Canada.
authors.forename: Majid A
authors.initials: MA
authors.lastname: Almadi
authors.forename: Alan N
authors.initials: AN
authors.lastname: Barkun
authors.forename: Myriam
authors.initials: M
authors.lastname: Martel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001650:Bile Duct Neoplasms / Q000601:surgery*; D002761:Cholangitis / Q000453:epidemiology; D002764:Cholecystitis / Q000453:epidemiology; D002779:Cholestasis / Q000601:surgery*; D005260:Female; D006470:Hemorrhage / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010195:Pancreatitis / Q000453:epidemiology; D016032:Randomized Controlled Trials as Topic; D015607:Stents / Q000009:adverse effects*; D016896:Treatment Outcome