ENC Health Currents: New Study Finds Colonoscopies May Prompt Appendicitis

Mar 7, 2018

Dr. Marc D. Basson, a medical researcher at the UND School of Medicine and Health Sciences, led a team that published an article, titled “Colonoscopy is associated with increased risk of appendicitis,” published in October by JAMA Surgery, the surgical offshoot of the Journal of the American Medical Association.
Credit UND SMHS.

Even though thousands of colonoscopies are done every year with minimal side effects, a new study from the University of North Dakota finds that the procedure may be linked with an increased risk of developing appendicitis.  


Like any medical procedure, there are potential risks associated with colonoscopies such as abdominal swelling or cramping, bleeding and in rare cases perforation of the intestinal wall.  But appendicitis isn’t on the list of side effects doctors discuss with patients before the procedure.  Dr. Marc Basson is the Senior Associate Dean for Medicine and Research at the University of North Dakota School of Medicine and Health Sciences. 

“We didn’t know if this was simply a coincidence or whether this was actually a causal event in some way and that’s what lead us to do this study.”

The idea that colonoscopies may trigger appendicitis came one evening when Dr. Basson was on call in the ER.  A patient who had a colon cancer screening a few days prior was presenting symptoms of appendicitis. 

“Of course, the inevitable question that the patient asks is did something go wrong? Did that other doctor do this to me?  And of course, I said no, no it’s just a common thing.  Then we actually had a couple of other patients over the next… I can’t remember…a year or so who similarly had that coincidental effect.”

Dr. Basson and a team of colleagues from the University of North Dakota School of Medicine and Health Sciences began their research in 2016 poring over records from the Department of Veterans Affairs’ national database.  They used diagnostic codes to identify 400,000 veterans across the United States who had a screening colonoscopy between January 2009 and June 2014.

“Then we asked the question among those roughly 400,000 patients, how many had appendicitis in the following year and in that year, did it happen in the first week or the next 51 weeks which was sort of our control group.”

The answer, Dr. Basson says depends on how you ask the question because of differences in the coding procedures and discrepancies in administrative data. 

“No matter how we asked the question, your chance of getting appendicitis or having an appendectomy in the week after your screening colonoscopy if you were one of these 400,000 roughly veterans was somewhere between four and a half and ninefold increased over the chance in any subsequent week of the rest of the year that you would have appendicitis or have an appendectomy.”

This new research brings to light side a possible side effect of colon cancer screening and informs patients on a potential risk.  It may also help doctors diagnose appendicitis as post-colonoscopy abdominal pain.  The recent findings line up with studies done in 2007 and 2013 that found acute appendicitis was caused by colonoscopy.  We reached out to several gastroenterologist in eastern North Carolina for comment on the study with no takers.  I did speak with the Associate Professor of Medicine in the Division of Gastroenterology at Duke Health Dr. Dan Wild.  He believes the risk of developing appendicitis following colonoscopy is very low.

“I can tell you I’ve done approximately 10,000 colonoscopies in my career and I’ve had one patient develop appendicitis within a few days of the procedure.” 

Dr. Wild says it may be true that the chance of developing appendicitis a week after the procedure is greater. But the numbers tell the whole story.

“If you look at their actual data, when they looked at more than just the diagnostic codes and they actually delved into these patients to determine who actually had appendicitis, they found only 12 patients.  So the actual number of this 400,000 patients who underwent colonoscopy over a five year period, only 12 developed appendicitis.”

Even though appendicitis caused by colonoscopy is extremely rare, the study is still significant because it presents another complication to consider after having a colonoscopy. Dr. Basson hopes to conduct further testing to figure out why it’s happening.   He says it could have something to do with the cleanout…

“Medications that give you massive diarrhea to clean everything out.”

…before a procedure.

“One particular kind of cleanout actually does make the colon what we call ischemic, which means it decreases the blood flow to the colon.”

Another possibility is that the cleanout disrupts the bacteria that live in the colon.

“That changes the microbial contents of your bowel”

It’s also possible that the air pressure necessary to perform a colonoscopy may have effects on the colonic mucosa that can result in appendicitis.  In a case report from Staten Island University Hospital, a patient underwent a screening colonoscopy and developed acute appendicitis a few days later. It was determined to have been caused by the introduction of a fecalith or impaction of stool into the appendix.

In any case, Dr. Basson admits more research needs to be done to confirm these findings and adds the current study has some drawbacks.

“This study was done in veterans. So these are almost all, not all, but almost all men.  Clearly, women are underrepresented in the VA population.  We don’t even really know if this applies to women, although we suspect it does.”

He also worries that people who hear about the findings may avoid getting a colonoscopy.

“These risks are still very, very low.  That’s why we needed to look at 400,000 patients to figure it out.  So we are not in any way suggesting that people should be afraid to get a colonoscopy because they might get appendicitis.”

There are noninvasive ways to screen for colon cancer at home, such as a stool sample collection kits.  However, they require a prescription from a doctor.   And, while they may be good at detecting cancer, Dr. Wild with Duke Health adds they’re not effective at catching precursor lesions. 

“Studies have shown that their ability to detect even large polyps are as low as 30 to 40 percent.  In my mind, that’s just not optimal because I would rather be able to catch a polyp and remove it and prevent someone from getting colon cancer rather than diagnose them after the cancer has developed.”

Colorectal cancer is the second leading cause of cancer death both in North Carolina and the United States.  Colonoscopy, even with potential side effects, is still considered the gold standard for screening.  If there’s any good news, it’s that if no adenomas or cancer are found, the next colonoscopy won’t be for another decade.