Some studies have shown that an appendectomy (removal of the appendix) is associated with a reduced risk of ulcerative colitis. The reverse is true for Crohn's disease -- some research has found an increased risk after appendectomy. Researchers are still unclear as to why these associations exist, and why appendectomies seem to have opposite effects on the risk of Crohn's disease and ulcerative colitis.
What's an Appendix?
This little organ is a mystery, as it has no proven function. It is located at the first branch of the intestine, and it looks like a worm or a tube. Even though it doesn't appear to do anything, it does get inflamed, which is called appendicitis.
Each year, one in 500 people has an appendectomy. If an inflamed appendix is not removed, it could burst. An appendix that has burst can cause a serious infection that could be fatal. Removal of the appendix doesn't appear to cause any further health problems.
The Connection to Ulcerative Colitis
Several studies suggest that removal of the appendix could lessen the risk of developing ulcerative colitis by as much as 69 percent. People who have ulcerative colitis are less likely to have had an appendectomy, either for appendicitis or another reason, than the general population.
There are currently three theories as to why people with ulcerative colitis have had fewer appendectomies than healthy people.
- An antigen in the appendix is associated with the onset of ulcerative colitis.
- Abnormalities in the intestine among people predisposed to ulcerative colitis may be responsible for fewer instances of appendicitis.
- Having an appendectomy somehow protects a person from developing ulcerative colitis.
The last theory has been tested in animals. Animals whose appendix was removed were less likely to develop ulcerative colitis. Animals who had an appendectomy at two weeks were also discovered to be free of the bacteria Bacteroides. This organism may trigger intestinal inflammation in IBD. Researchers conclude that this may mean the appendix does have a use after all. The appendix may play a part in the mucosal immune system, which defends the body against infection.
The impact of removing the appendix after the onset of ulcerative colitis is unknown. Overall, the relationship between ulcerative colitis and appendectomy remains unclear.
The Connection to Crohn's Disease
Two studies have concluded that the risk of Crohn’s disease increases in the 20 years after removal of the appendix; women in particular had the highest risk of developing Crohn's disease after an appendectomy, according to the first study.
The researchers in the second study hypothesize that, in some patients, the original attack of appendicits may have actually been the first flare of Crohn's disease. The Crohn's symptoms are mistaken for appendicitis and an appendectomy is done. Only years later is the Crohn's finally diagnosed. Therefore, the risk of Crohn's in those who have had an appendectomy may not truly be increased. The researchers conclude that additional research is necessary to understand any connection between Crohn’s disease and appendectomy.
More Study is Needed
This evidence does not mean that we should all rush out and urge our close family members who are at risk for ulcerative colitis to have appendectomies. Nor should it factor into a decision to remove an appendix for a person who is at risk for Crohn’s disease. The evidence is not compelling enough to warrant major surgery or to prevent a necessary appendectomy. Any type of surgery carries a number of risks, and those risks may not outweigh the potential benefits.Sources:
Andersson RE, Olaison G, Tysk C, Ekbom A. "Appendectomy is followed by increased risk of Crohn's disease." Gastroenterology Jan 2003. 06 Sept 2013.
Gilaad G Kaplan, Bo V Pedersen, Roland E Andersson, Bruce E Sands, Joshua Korzenik and Morten Frisch. "The risk of developing Crohn's disease after an appendectomy: A population-based cohort study in Sweden and Denmark." Gut Sept 2007. 06 Sept 2013.
Koutroubakis IE, Vlachonikolis IG, Kouroumalis EA. "Role of appendicitis and appendectomy in the pathogenesis of ulcerative colitis: a critical review." Inflamm Bowel Dis Jul 2002. 06 Sept 2013.
Roland E. Andersson, Gunnar Olaison, Curt Tysk, and Anders Ekbom. "Appendectomy and Protection against Ulcerative Colitis." N Engl J Med 15 Mar 2001. 06 Sept 2013.