title: Tonsillectomy and the risk of inflammatory bowel disease: A systematic review and meta-analysis.
abstract: OBJECTIVE
  Tonsillectomy remains a controversial environmental factor in the etiology of inflammatory bowel disease (IBD). This meta-analysis aims to elucidate a more defined role of tonsillectomy in the development of IBD.
  
  
  METHODS
  Four databases, including PubMed, EMBASE, the Cochrane Library, and Web of Science, were searched for studies exploring the association between tonsillectomy and the risk of IBD. The pooled estimates of odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using a random effects model. Heterogeneity was assessed using chi-squared and I(2) statistical analysis. A funnel plot was performed to assess publication bias.
  
  
  RESULTS
  A total of 23 observational studies involving 19 569 patients were included in our meta-analysis. Of these, 17 studies investigated the association between tonsillectomy and Crohn's disease (CD), and 22 studies explored its relationship with ulcerative colitis (UC). Overall, a positive relationship between tonsillectomy and development of CD (OR 1.37, 95% CI: 1.16-1.62) was observed, while there was no association between tonsillectomy and UC (OR 0.94, 95% CI: 0.84-1.05). When ORs were adjusted for smoking, the pooled OR for CD increased to 1.66 (95% CI: 1.03-2.68) and, for UC, changed to 1.03 (95% CI: 0.74-1.44).
  
  
  CONCLUSIONS
  This meta-analysis demonstrates that tonsillectomy is associated with an increased risk of developing CD. We found no evidence to suggest that tonsillectomy exerts a protective effect on the development of UC, as is the case with appendectomy. Further prospective studies are required to confirm the validity of these observations.
authors.affiliation: Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China.
authors.forename: Weili
authors.initials: W
authors.lastname: Sun
authors.affiliation: Department of Gastroenterology, the First People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Han
authors.affiliation: Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Wu
authors.affiliation: Division of Gastroenterology and Hepatology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Institute of Digestive Disease, Shanghai, China.
authors.forename: Chuanhua
authors.initials: C
authors.lastname: Yang
mesh_terms: D016009:Chi-Square Distribution; D003093:Colitis, Ulcerative / Q000175:diagnosis / Q000209:etiology; D003424:Crohn Disease / Q000175:diagnosis / Q000209:etiology*; D006801:Humans; D016017:Odds Ratio; D011379:Prognosis; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014068:Tonsillectomy / Q000009:adverse effects*
keywords: humans; inflammatory bowel diseases; meta-analysis; risk factor; tonsillectomy