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Colonoscopy may be associated with appendicitis
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Appendicitis occurred approximately seven times more frequently in the week following colonoscopy, according to study results from a large Veterans Administration cohort.
Marc D. Basson, MD, PhD, MBA, professor of surgery, pathology and biomedical science and senior associate dean for medicine and research at University of North Dakota School of Medicine & Health Sciences, and colleagues investigated the potential association between colonoscopy and appendicitis in a cohort of 392,485 individuals from the VA health system.
Results showed the risk for ICD-9 or CPT codes for appendicitis or appendectomy increased fivefold to ninefold in the week after colonoscopy. Researchers observed no such increase for appendectomy coding in the week following bronchoscopy, knee replacement, arthroscopy or cataract surgery.
HemOnc Today spoke with Basson about the results and their potential implications.
Question: Why did you hypothesize there might be an association between colonoscopy and appendicitis?
Answer: I have had a few patients with appendicitis who had recently undergone colonoscopy by another physician. The patients asked if the two events were related, and they sometimes asked if the colonoscopist had done anything wrong. We reviewed the literature on this subject in 2013 and discovered that this is actually a fairly common experience. However, colonoscopy is common and appendicitis is common, so it is predictable that they will sometimes happen within the same week. We, therefore, needed to determine whether this was occurring by random chance or whether there was some real association. To get the large numbers needed to answer this question, we went to the U.S. Department of Veterans Affairs system and, after obtaining appropriate permissions, compared the incidence of appendicitis within a week after screening colonoscopy with the weekly incidence of appendicitis for the rest of that year, or over each of the following 51 weeks. There were several different ways to define and analyze our results, but no matter how we looked at the information, there was a substantially increased risk of appendicitis — typically about sevenfold — within the week after colonoscopy. These were patients who didn’t have tumors of the appendix, who weren’t biopsied there, and who didn’t have any particular abnormality on colonoscopy that would have predicted this outcome, so it seems to be a very real effect.
Q: Can you explain this association?
A: We don’t believe that these colonoscopies were done incorrectly or that the appendix was injured in some way. There are at least three different explanations that we could imagine. First, the cleanout required for colonoscopy is likely to affect the bacteria living in the colon, and this might predispose to appendicitis. Second, some cleanouts are known to temporarily alter the blood supply to the colon in some cases, and this might predispose to appendicitis. Third, the gas pressure within the colon from the colonoscopy itself might affect the lining of the colon in a way that might predispose to appendicitis. Distinguishing among these possibilities will require further study.
Q: Might this alter colorectal cancer screening protocols?
A: The risk for appendicitis after colonoscopy, although perhaps seven times normal, is still very low. We don’t believe that this should alter colorectal cancer screening protocols or deter patients from having a colonoscopy. If we can learn more about how and why this happens, then this might cause us to alter our bowel cleanout preparation or colonoscopy technique in some way to further reduce the risk. It’s more important right now that we know about the problem so that if patients develop right lower quadrant abdominal pain after colonoscopy, we can be alert to this possibility and not just dismiss this as pain from retained gas.
Q: Should clinicians be on the lookout for appendicitis among patients who recently underwent colonoscopy?
A: If any clinician — whether a surgeon, a gastroenterologist, an oncologist, or a primary care practitioner — has a patient who has had a colonoscopy within the past week and then complains of right lower quadrant abdominal pain, it would be appropriate to consider appendicitis much higher in the differential diagnosis than we would have previously. Appendicitis is relatively less common in people aged older than 50 years, who are the folks who are generally having colonoscopy, so it’s not usually high on our list.
Q: What is the next step?
A: We don’t know enough to plan a clinical trial at this point. What’s needed is more scientific investigation to distinguish among the competing explanations for mechanism that I’ve mentioned above, or to find some mechanism that we haven’t thought about yet. – by Rob Volansky
Reference:
Basson MD, et al. JAMA Surgery. 2018;doi:10.1001/jamasurg.2017.3790.
Shaw D, et al. World J GI Surgery. 2013;5:259-263.
For more information:
Marc D. Basson, MD, PhD, MBA, can be reached at North Dakota School of Medicine & Health Sciences, 1301 N. Columbia Road, Stop 9037, Grand Forks, ND 58202; email: marc.basson@med.und.edu.
Disclosure: Basson reports no relevant financial disclosures.