The Link Between Appendectomy, Ulcerative Colitis, and Crohn's Disease

The removal of the appendix may have a role in developing Crohn's or colitis

Woman with irritable bowel syndrome

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Several studies have explored the connection between the inflammatory bowel diseases (IBD)—Crohn's disease and ulcerative colitis—and the appendix.

Some research has shown that an appendectomy (the removal of the appendix) is associated with a reduced risk of developing ulcerative colitis. The reverse is true for Crohn's disease — some research has found there is an increased risk of developing the disease after appendectomy. Researchers are still unclear as to why these associations exist and why appendectomies appear to have opposite effects on the risk of Crohn's disease and ulcerative colitis.

It's typically not recommended to remove an appendix when it appears healthy. There is some debate over removing the appendix when surgery is being done for another reason: taking out the appendix because the surgeon is already doing another procedure. However, taking out an appendix in a healthy person because there may be a risk of that person developing ulcerative colitis one day isn't something that's done.

The Appendix

This little organ remains somewhat mysterious, as it has no verified function. It is located at the first branch of the large intestine, and it looks like a worm or a tube. Even though it doesn't appear to do anything overt, and people can live without one, it does get inflamed, which is a condition 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.

A Connection Between Appendectomy and Ulcerative Colitis

Several studies suggest that removal of the appendix could lessen the risk of developing ulcerative colitis by as much as 69%. 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.

  1. An antigen (a substance that stimulates an immune response) in the appendix is associated with the onset of ulcerative colitis.
  2. Abnormalities in the intestine among people already predisposed to ulcerative colitis may be responsible for fewer instances of appendicitis.
  3. Having an appendectomy somehow protects a person from developing ulcerative colitis.

The last theory has been tested on 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 that's associated with 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. However, if the colon is removed (a colectomy) to treat ulcerative colitis, the appendix is also removed (because it is attached to the colon).

The Connection Between Appendectomy and 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 appendicitis 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.

A Word From Verywell

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 either to warrant major surgery or to prevent a necessary appendectomy. Any type of surgery carries a number of risks, and until we know more, those risks may not outweigh the potential benefits.

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