APPENDECTOMY IS FOLLOWED BY INCREASED RISK OF CROHN'S DISEASE

Background & Aims: 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.