title: Meta-analysis: the risk of venous thromboembolism in patients with inflammatory bowel disease.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a systemic disorder that predominantly affects the bowels but is also associated with venous thromboembolism (VTE).
  
  
  OBJECTIVE
  To provide a quantitative assessment of the association of IBD with venous thromboembolism risk and to explore the possible sources of heterogeneity in the current literature, a meta-analysis of case-control and cohort studies was conducted.
  
  
  METHODS
  Studies were identified by a literature search of the PubMed and Scopus databases (from inception inclusive 31 December 2012) for English language studies. Summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated with fixed- and random-effects models. Several subgroup analyses were performed to explore potential study heterogeneity and bias.
  
  
  RESULTS
  Eleven studies met our inclusion criteria. The summary RR for deep venous thromboembolism (DVT) and pulmonary embolism (PE) comparing subjects both with and without IBD was 2.20 (95% CI 1.83-2.65). After adjusting for obesity and smoking, summary relative risks near 2.0 were seen for venous thromboembolism in both UC and CD patients.
  
  
  CONCLUSIONS
  This meta-analysis showed that inflammatory bowel disease is associated with an approximately two-fold increase in the risk of venous thromboembolism.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yuhara
authors.forename: C
authors.initials: C
authors.lastname: Steinmaus
authors.forename: D
authors.initials: D
authors.lastname: Corley
authors.forename: J
authors.initials: J
authors.lastname: Koike
authors.forename: M
authors.initials: M
authors.lastname: Igarashi
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Mine
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications*; D009765:Obesity / Q000150:complications; D011655:Pulmonary Embolism / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D054556:Venous Thromboembolism / Q000209:etiology*