title: Diagnosis underlying appendectomy and coeliac disease risk.
abstract: BACKGROUND
  Earlier studies suggest that appendectomy is associated with a substantially reduced risk of certain types of bowel inflammation such as ulcerative colitis, particularly where the underlying diagnosis is acute appendicitis. Previous research on appendectomy and coeliac disease is inconsistent, based on small numbers with retrospective data collection, and has not differentiated between different diagnoses underlying appendectomy.
  
  
  OBJECTIVE
  To investigate the association of diagnosis underlying appendectomy with coeliac disease.
  
  
  METHODS
  We used Cox regression to study the risk of later appendectomy in more than 14,000 individuals with coeliac disease and 68,000 referents without coeliac disease, identified through the Swedish National Registers 1964-2003, and conditional logistic regression to study the risk of coeliac disease associated with a history of prior appendectomy. Appendectomy was categorised according to the underlying diagnosis: perforated appendicitis, non-perforated appendicitis, and appendectomy without appendicitis.
  
  
  RESULTS
  Overall, coeliac disease was negatively associated with perforated appendicitis (hazard ratio=0.78, 95% confidence interval=0.60-1.01), not associated with non-perforated appendicitis (hazard ratio=1.11, 95% confidence interval=0.99-1.25), but positively associated with appendectomy without appendicitis (hazard ratio=1.58, 95% confidence interval=1.32-1.89). The magnitudes of the relative risks were similar irrespective of whether coeliac disease occurred prior to or after appendectomy.
  
  
  CONCLUSIONS
  Coeliac disease and perforated appendicitis are negatively associated irrespective of the timing of the conditions. Not surprisingly, CD increases the risk for appendectomy without appendicitis.
authors.affiliation: Department of Pediatrics, Orebro University Hospital, Sweden. jonasludvigsson@yahoo.com
authors.forename: J F
authors.initials: JF
authors.lastname: Ludvigsson
authors.forename: J
authors.initials: J
authors.lastname: Askling
authors.forename: A
authors.initials: A
authors.lastname: Ekbom
authors.forename: S M
authors.initials: SM
authors.lastname: Montgomery
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001062:Appendectomy / Q000706:statistics & numerical data*; D001064:Appendicitis / Q000453:epidemiology / Q000601:surgery; D002446:Celiac Disease / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012042:Registries; D018570:Risk Assessment; D013548:Sweden / Q000453:epidemiology