title: Appendectomy is followed by increased risk of Crohn's disease.
abstract: OBJECTIVE
  Appendectomy is associated with a low risk of subsequent ulcerative colitis. This study analyzes the risk of Crohn's disease after appendectomy.
  
  
  METHODS
  We followed-up 212,218 patients with appendectomy before age 50 years and a cohort of matched controls, identified from the Swedish Inpatient Register and the nationwide Census, for any subsequent diagnosis of Crohn's disease.
  
  
  RESULTS
  An increased risk of Crohn's disease was found for more than 20 years after appendectomy, with incidence rate ratio 2.11 (95% confidence interval [CI], 1.21-3.79) after perforated appendicitis, 1.85 (95% CI, 1.10-3.18) after nonspecific abdominal pain, 2.15 (95% CI, 1.25-3.80) after mesenteric lymphadenitis, 2.52 (95% CI, 1.43-4.63) after other diagnoses. After nonperforated appendicitis, there was an increased risk among women but not among men (incidence rate ratio 1.37; 95% CI, 1.03-1.85, respectively, 0.89, 95% CI, 0.64-1.24). Patients operated on before age 10 years had a low risk (incidence rate ratio 0.48, 95% CI, 0.23-0.97). Crohn's disease patients with a history of perforated appendicitis had a worse prognosis.
  
  
  CONCLUSIONS
  Appendectomy is associated with an increased risk of Crohn's disease that is dependent on the patient's sex, age, and the diagnosis at operation. The pattern of associations suggests a biologic cause.
authors.affiliation: Department of Surgery, County Hospital Ryhov, SE-551 85 Jönköping, Sweden. roland.andersson@ltjkpg.se
authors.forename: Roland E
authors.initials: RE
authors.lastname: Andersson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Olaison
authors.forename: Curt
authors.initials: C
authors.lastname: Tysk
authors.forename: Anders
authors.initials: A
authors.lastname: Ekbom
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001062:Appendectomy / Q000009:adverse effects* / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D035061:Control Groups; D003424:Crohn Disease / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D018570:Risk Assessment; D012737:Sex Factors