Apparent Risk of Crohn's Disease After Appendectomy Explained

A new study suggests that an evident transient increased risk of Crohn's disease after an appendectomy may be attributable to diagnostic bias.

Researchers of the Statens Serum Institut (Copenhagen, Denmark) studied data on 443,761 Swedish appendectomy patients and 265,592 Danish appendectomy patients who were followed for first hospitalizations for Crohn's disease. The median age at appendectomy was 26 years and the subjects were followed for an average of 15.6 years (11.1 million person-years). A total of 1655 Crohn's disease cases were observed during follow-up.

Overall, the standardized incidence ratio (SIR) of Crohn's disease after an appendectomy was 1.52. No association was observed between appendectomy before the age of 10 years and the risk of Crohn's disease (SIR 1.00). The highest risk of Crohn's disease was observed in the first 6 months after appendectomy (SIR 8.69). The risk of Crohn's disease diminished quickly after that, and the risk reached background levels five to ten years after the appendectomy. The study was published in the October 2007 issue of Gut.

"Patients who underwent an appendectomy with a non-inflamed appendix remained at a significantly elevated risk for up to 20 years,” concluded Dr. Morten Frisch, Ph.D., and colleagues of the epidemiology research unit. "These findings can be explained by well-known differential diagnostic problems that may result in unnecessary appendectomies in some patients who present with symptoms of incipient Crohn's disease. Such cases of Crohn's disease will probably come to the clinician's attention after the appendectomy, a bias that is likely to be most pronounced within the first few years after an appendectomy.”


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Statens Serum Institut