Could a colonoscopy put you at risk for appendicitis?

In a recent study, scientists have suggested that patients who have undergone a colonoscopy may develop appendicitis a week after the procedure. The finding, which was published in JAMA Surgery, offers a new perspective on appendicitis and whether certain people are predisposed to it.

While cases of appendicitis have been generally declining for the past couple of years, it still affects around seven percent of Americans every year. This has led researchers to conduct new inquiries on whether factors such as the environment, lifestyle or genetics play a role in the development of the condition, even in its decline.

The research, led by Dr. Marc Basson and his team from the University of North Dakota, tackles what has been theorized by previous researchers and offers new answers to the table. “A number of my patients had undergone colonoscopies by different providers. Then I saw these patients and they had appendicitis, some within a couple of days of the colonoscopy,” he explained in an article in Newswise. “And the patient would ask something like, ‘Gosh, did the colonoscopist do something wrong—why do I have appendicitis now?’ But since both colonoscopy and appendicitis are common things, the question became: Is there a real correlation here, or are these two random events that were just occurring together by chance?”

For the study, the team first gained approval and a waiver of informed consent from the University of North Dakota and the Fargo Veteran Affairs Medical Center, allowing them to look at screening codes from the U.S. Department of Veterans Affairs. In particular, they looked at data for colonoscopy cases between January 2009 and June 2014. Incomplete colonoscopy and sigmoidoscopy codes were excluded from the study. The team identified a total of 392,485 cases. They looked at the year after the procedures were undertaken, looking at codes for appendectomy and appendicitis. For the findings, they calculated the incidence rate ratio (IRR) for appendicitis a week after a colonoscopy and for the following weeks at a confidence interval of 95 percent. (Related: Sigmoidoscopy proven to be a better option than colonoscopy.)

Researchers found out that cases of appendicitis or an appendectomy were coded more frequently a week following a colonoscopy. The results were the same even if the cases were broken down to reflect their respective age groups. On the first week, they found that 26 cases were coded for appendicitis, while 10 were coded for an appendectomy. The incidence rate was higher compared to other procedures such as bronchoscopy, knee replacement surgery, cataract surgery, or knee arthroscopy. Moreover, 12 patients were coded to have appendicitis and had an appendectomy a week following a colonoscopy. Over the following weeks, 79 patients were identified to have appendicitis.

While the correlation between a colonoscopy and the increased risk of appendicitis is still unclear, the study offers some speculation. In particular, these include asking whether the changes in bacteria within the colon before a colonoscopy can increase the likelihood of inflammation, or whether the increased air pressure caused by it can affect colonic mucosa and cause predisposition to appendicitis.

The team clarified, however, that this study only indicates that there is an association between colonoscopy and appendicitis, but it does not discourage patients from going under the procedure when needed.

At the end of the day, Dr. Basson explained, this study points out that there is more work to be done to learn more about this correlation.

“My hope is that this study will spur more conversation, more studies, so we can learn more about all of this,” he said. “There’s clearly more going on biologically with the appendix than we thought there was 100 years ago.”

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