HealthDay News — The risk of appendicitis is increased in the week following colonoscopy, according to a research letter published in the January issue of JAMA Surgery.

Marc D. Basson, MD, PhD, from the University of North Dakota School of Medicine and Health Sciences in Grand Forks, and colleagues identified 392,485 veterans with a screening colonoscopy code between January 2009 and June 2014. Over the following year the authors sought a Current Procedural Terminology (CPT) code for appendectomy, an International Classification of Diseases, Ninth Revision (ICD-9) code for appendicitis, both CPT and ICD-9 codes, or the appendectomy CPT code with a discharge diagnosis of appendicitis. The incidence rate ratio (IRR) for appendicitis within one week after undergoing a colonoscopy was calculated. 

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The researchers found that there were more frequent codes for appendicitis or an appendectomy one week after a colonoscopy than in the following 51 weeks. This result was not affected by age subgrouping, and there was no increase in appendicitis in weeks two to four. Within the cohort, there was no increase in appendectomy one week after bronchoscopy, knee replacement procedure, cataract surgery, or knee arthroscopy. The IRR was 6.8 for appendicitis within a week after colonoscopy considering only validated patients from the CPT-based strategy.

“These results suggest that undergoing a colonoscopy predisposes patients to appendicitis within one week,” the authors write. “The mechanism of this effect awaits elucidation.”

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