The appendix – and its inflammation requiring appendectomy – may be related to risk of future inflammatory bowel disease. A 2003 study suggests that removal of the appendix may decrease the risk of ulcerative colitis while a study by the same authors from 2001 suggests its removal may also increase the risk of Crohn’s disease.

A cohort of 212,218 patients (taken from the Swedish Inpatient Registry) who had an appendectomy performed before the age of 50 – and a matched control group – was included in both studies. The groups were examined for subsequent development of ulcerative colitis, in the first study, and Crohn’s disease in the second.

It is important to note that the results were reported in patients who had their appendix removed for inflammation, and not for non-specific abdominal pain. The authors consider it significant that the appendix had been inflamed. They do not recommend removal of the appendix as a protection against ulcerative colitis.

The study authors tried to understand what the mechanism was to either increase or decrease the risk of future inflammatory bowel disease. The authors speculate that the appendix has some influence on the immune system. It’s unclear, however, if appendicitis increases the risk of Crohn’s disease, or if people at risk for Crohn’s disease are more likely to develop appendicitis.

The study reported in the January 2003 issue of the journal Gastroenterology found that people who had their appendix removed were 47% more likely to develop Crohn’s disease than those who did not have the surgery. However, the risk of developing the relatively rare condition was still low overall. The increased risk was present soon after surgery, and was still present ten years later.

It may seem odd that appendectomy is associated with a decreased risk of ulcerative colitis but an increased risk of Crohn’s disease since both are inflammatory bowel diseases. This apparent contradiction may be explained by the different nature of the inflammatory responses found in ulcerative colitis and Crohn’s disease and the other differences between the two conditions. Ulcerative colitis only involves the large bowel and always starts at the anus. Crohn’s disease usually involves the last part of the ileum (terminal ileum), but can involve the large bowel in about 30-50% of patients. Also, in ulcerative colitis, the inflammation usually involves only the inner mucosa, while in Crohn’s disease the inflammation extends right through the mucosa and into the muscle.


Conflicting Reports

A much smaller study from Australia (using the Brisbane Inflammatory Bowel Disease database and the Australian Twin Registry) reported in the journal Gut in December 2002 shows that appendix removal before age 20 may delay the onset of both ulcerative colitis and Crohn’s disease – and could even result in a milder case of either disease. In this study, the appendix removal statistics were the most compelling in that the control subjects were more than three times as likely to have had their appendix removed as patients with ulcerative colitis – and more than twice as likely as those with Crohn’s disease. Those who had their appendix removed before age 20 were likely to have a milder case of ulcerative colitis. They also developed Crohn’s disease at an older age.

Among people with inflammatory bowel disease, those who had their appendix removed did not require as much surgery or immune suppressing drugs as those who had not had their appendix removed. Those diagnosed at an older age, and who had their appendix removed at that time, also had an easier time with their disease.

The researchers say the link behind this novel association may lie in the immune system. When the appendix is removed early in life, the intestines may become immune deficient. This could be an advantage for those people with a genetic predisposition to inflammatory bowel disease, where the immune deficiency may have a protective effect against those problems.

First published in the Inside Tract® newsletter issue 135 – January/February 2003
1. G L Radford-Smith, J E Edwards, D M Purdie, et al. Protective role of appendicectomy on onset and severity of ulcerative colitis and Crohn’s disease. Gut 2002;51:808-813.
2. R E Anderson, G Olaison, C Tysk, E Ekbom. Appendectomy and Protection Against Ulcerative Colitis. New England Journal of Medicine 2001;344:808-814.
3. R E Anderson, G Olaison, C Tysk, E Ekbom. Appendectomy is followed by increased risk of Crohn’s disease. Gastroenterology 2003;124:40-46.