Elsevier

Surgery

Volume 130, Issue 1, July 2001, Pages 36-43
Surgery

Original Communications
Appendectomy and subsequent risk of inflammatory bowel diseases*,**

https://doi.org/10.1067/msy.2001.115362Get rights and content

Abstract

Background. Case-control studies have reported an inverse relationship between appendectomy and the risk of ulcerative colitis, but the association has not been confirmed in prospective studies. Methods. Using national hospital discharge registry data in Denmark, the authors followed up 154,434 patients who underwent appendectomy during the period 1977 to 1989 to investigate whether they had subsequent hospitalizations for ulcerative colitis and Crohn's disease. Ratios of observed-to-expected first hospitalizations for inflammatory bowel diseases served as measures of the relative risk (RR). Results. Hospitalization for ulcerative colitis occurred in 84 patients who had appendectomies versus 97.0 expected (RR = 0.87; 95% CI, 0.69-1.07). RRs were not significantly reduced in subgroups defined by sex, age, time since appendectomy, calendar period, or cause of appendectomy. Hospitalization for Crohn's disease occurred in excess (RR = 2.88; 95% CI, 2.45-3.39; n = 150), notably in the first year after appendectomy (RR = 10.83; 95% CI, 8.49-13.62; n = 73); but after 5 years, the RR was not significantly elevated. Conclusions. This large population-based cohort study failed to support a significant inverse association between appendectomy and ulcerative colitis risk in the first decade after the operation. The excess of Crohn's disease shortly after appendectomy most likely reflects differential diagnostic problems in patients newly presenting with abdominal pain. (Surgery 2001;130:36-43.)

Section snippets

Methods

Since 1977, a nationwide registration system has recorded more than 99% of all hospitalizations in Denmark.23 For each hospitalization, the register contains the 10-digit personal identifier (incorporating codes for sex and date of birth) unique to each citizen in Denmark, date of discharge, surgical procedures, and medical discharge diagnoses. Procedures are coded according to a national classification system,24 and diagnoses are coded according to a Danish version of the International

Results

Our cohort of 154,434 appendectomy patients (40% men, 60% women) included 10% who had the operation because of perforating appendicitis and 49% who had other appendiceal disease (Table I).

. Characteristics of 154,434 patients followed up for inflammatory bowel disease after appendectomy in Danish hospitals, 1977-1989

Empty CellMenWomenTotalPerson-years*Average follow-up (y)
Empty CellNo.%No.%No.%Empty CellEmpty Cell
Year of appendectomy
1977-198019,90332%31,17334%51,07633%536,79510.5
1981-198419,56831%29,33132%48,89932%329,9356.7
1985-1989

Discussion

This cohort study fails to support the previously reported association between appendectomy and risk of ulcerative colitis. We had considerable power to detect as statistically significant risk reductions of between 36% and 98% as reported in previous studies.4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Indeed, our overall estimate of the RR (RR = 0.87; 95% CI, 0.69-1.07) excludes a reduction in the risk of ulcerative colitis after appendectomy of more than 31% and, being close

Conclusion

This study, the first based on prospective data from a large population-based cohort study, does not support a relationship between appendectomy and ulcerative colitis in the first decade after appendectomy. The association with Crohn's disease most likely reflects differential diagnostic problems in patients with abdominal pain. Additional cohort studies with longer follow-up are warranted, as are case-control studies of incident cases of ulcerative colitis and population controls using

Addendum

Since submission, 2 additional case-control studies and 1 follow-up study have been published.44, 45, 46 Both case-control studies had methodological problems as seen in prior studies, including unmatched analysis of matched data,44 use of different methods for ascertaining appendectomies in cases and controls,45 and failure to specify the ascertainment period for appendectomies among controls.44, 45 A follow-up study in Sweden46 compared incident hospitalization rates for ulcerative colitis

Acknowledgements

We thank Andrea Bautz for skillful computer assistance and Drs Charles S. Rabkin, Michie Hisada, and Henrik Hjalgrim for fruitful discussions of the study subject.

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    *

    Supported by research grant MAO NO1-CP-85639-04 from the National Cancer Institute, Bethesda, MD, and by grants from Direktør E. Danielsen og Hustrus Foundation, The Foundation for the Advancement of Medical Science, Grosserer L. F. Foghts Foundation, Lily Benthine Lunds Foundation, and the Danish Medical Research Council.

    **

    Reprint requests: Dr Morten Frisch, Department of Epidemiology Research, Danish Epidemiology Science Center, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen, Denmark.

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