title: The risk of developing Crohn's disease after an appendectomy: a meta-analysis.
abstract: BACKGROUND
  Studies exploring the association between appendectomy and Crohn's disease (CD) have reported conflicting findings. We conducted a systematic review of the literature and a meta-analysis to assess the risk of CD following an appendectomy and determine the effect of time between appendectomy and CD diagnosis.
  
  
  METHODS
  MEDLINE was used to identify observational studies evaluating the association between appendectomy and CD. Authors were contacted when data were insufficient. Relative risks (RR) with 95% confidence intervals (CI) were calculated using a random effects model. Studies that analyzed their data by the interval between the appendectomy and the diagnosis of CD were assessed separately. The Woolf chi(2) statistic was used to test for homogeneity. Egger's test was used to evaluate publication bias.
  
  
  RESULTS
  The summary RR estimate for CD following an appendectomy was significantly elevated (RR 1.61, 95% CI 1.28-2.02), though heterogeneity was observed (P < 0.0001). The risk was elevated within the first year following the operation (RR 6.69, 95% CI 5.42-8.25). The risk of CD was also significantly increased 1-4 yr following an appendectomy (RR 1.99, 95% CI 1.66- 2.38); however, after 5 yr or more, the risk fell to baseline levels (RR 1.08, 95% CI 0.99-1.18). Publication bias was not detected (P = 0.2).
  
  
  CONCLUSIONS
  The meta-analysis demonstrated a significant risk of CD following an appendectomy, though heterogeneity was observed between the studies. The elevated risk early after an appendectomy, which diminishes thereafter, likely reflects diagnostic problems in patients with incipient CD.
authors.affiliation: Inflammatory Bowel Disease Clinic, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Gilaad G
authors.initials: GG
authors.lastname: Kaplan
authors.forename: Timothy
authors.initials: T
authors.lastname: Jackson
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Sands
authors.forename: Morten
authors.initials: M
authors.lastname: Frisch
authors.forename: Roland E
authors.initials: RE
authors.lastname: Andersson
authors.forename: Joshua
authors.initials: J
authors.lastname: Korzenik
mesh_terms: D001062:Appendectomy / Q000009:adverse effects*; D003424:Crohn Disease / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D012307:Risk Factors