The risk of developing Crohn's disease after an appendectomy: A population-based cohort study in Sweden and Denmark

Gilaad G Kaplan ¹, Bo V Pedersen ², Roland E Andersson ³, Bruce E Sands ¹, Joshua Korzenik ¹ and Morten Frisch ^2*

¹ Massachusetts General Hospital Crohn's and Colitis Center & Harvard University, United States
² Statens Serum Institut, Denmark
³ University Hospital, Linköping, Sweden

^* To whom correspondence should be addressed. E-mail: mfr{at}ssi.dk.

Accepted 24 April 2007

Abstract

Background: The relationship between appendectomy and Crohn's disease (CD) is controversial. We conducted a Swedish-Danish cohort study to assess the risk of developing CD after an appendectomy.

Methods: 709,353 appendectomy patients in Sweden (since 1964) and Denmark (since 1977) were followed for first hospitalizations for CD through 2004. Standardized incidence ratios (SIRs) served as relative risks.

Results: Overall, 1655 CD cases were observed during 11.1 million person-years of follow-up. While appendectomy before age 10 was not associated with CD risk (SIR = 1.00; 95% confidence interval (CI): 0.80 - 1.25), the overall SIR of developing CD was 1.52 (95% CI: 1.45 - 1.59), being highest in the first 6 months (SIR = 8.69; 95% CI: 7.68 - 9.84). SIRs diminished rapidly thereafter, with CD risk reaching background levels after 5-10 years for CD overall, as well as for Crohn's ileitis, ileocolonic CD, Crohn's colitis and other/unspecified CD. Long-term increased CD risk up to 20 years after the appendectomy was seen only in appendectomy patients without appendicitis or mesenteric lymphadenitis.

Conclusion: The transient increased risk of Crohn's disease following an appendectomy is likely explained by a diagnostic bias.

Keywords: appendectomy, appendicitis, epidemiology, inflammatory bowel disease, risk factor

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