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The prevalence and risk for colorectal cancer (CRC) is low among most patients with diverticulitis, but it is higher in patients with complicated diverticulitis, according to a new study.

Colonoscopy often is recommended to patients following a diverticulitis episode to rule out CRC being misdiagnosed as diverticulitis, but evidence supporting this practice is limited, wrote senior author Anne Peery, MD, associate professor of medicine in gastroenterology and hepatology at the University of North Carolina at Chapel Hill and colleagues.

Because the risk is poorly defined, the researchers investigated the prevalence and odds of CRC in patients with diverticulitis.

Overall, CRC risk "was much smaller than the current literature predicts," Peery told Medscape Medical News. However, for patients with complicated diverticulitis, the risk was more than three times higher, the researchers found.

"We'd like to highlight the importance of follow-up colonoscopy after recovery from complicated diverticulitis," Peery said.

The review was published online in Clinical Gastroenterology and Hepatology.

Analyzing Cancer Risk

Using data from the Gastrointestinal Quality Improvement Consortium registry, the researchers performed a cross-sectional study of patients aged 40-89 years with outpatient screening colonoscopies or follow-up colonoscopies after diverticulitis at 779 US sites between January 2012 and December 2021. The primary outcome was CRC, and the secondary outcome was advanced colorectal neoplasia (ACN).

The research team identified almost 4.6 million outpatient average-risk screening colonoscopies and nearly 92,000 follow-up colonoscopies in patients with any indication of diverticulitis and potentially additional indications. Those with a diverticulitis indication were more likely to be women and White individuals and to have a higher American Society of Anesthesiologists class than those who underwent screening colonoscopies.

Overall, CRC prevalence was 0.33% in screening colonoscopies and 0.31% across diverticulitis follow-up colonoscopies. Patients with diverticulitis were less likely to have CRC (adjusted odds ratio [aOR], 0.84) than those with screening colonoscopies.

In both groups, CRC prevalence increased with age and remained similar or less prevalent in the diverticulitis group.

Among 22,312 patients who underwent colonoscopy for diverticulitis only, CRC prevalence decreased to 0.17%. Patients with diverticulitis as the only indication were less likely to have CRC (aOR, 0.49) than those with screening colonoscopies.

CRC prevalence increased to 1.43% in 421 patients with complicated diverticulitis (with abscess or perforation). Patients with complicated diverticulitis were more likely to have CRC (aOR, 3.57) than those with screening colonoscopies.

In addition, ACN prevalence was 6.9% in screening colonoscopies, 5.2% in diverticulitis follow-up colonoscopies, 4.3% in the subgroup of colonoscopies performed for diverticulitis only, and 8.1% in the subgroup with complicated diverticulitis. Generally, ACN prevalence increased with age and was similar among the groups.

Patients with diverticulitis are more likely to have undergone a colonoscopy recently than patients getting screening colonoscopy, which likely explains the lower risk for CRC and ACN for patients with uncomplicated diverticulitis, the researchers wrote.

More than a third of diverticulitis follow-up colonoscopies occurred among patients aged 40-54 years. CRC prevalence was low at 0.2%-0.3% and similar to the screening colonoscopies group, but these patients need thoughtful clinical follow-up, according to the study authors.

"In older patients with diverticulitis, follow-up colonoscopy should include consideration of the patient's overall health status, whether alarm symptoms are present, family history of CRC, findings on any prior colonoscopies, and any notation of concern on imaging," Peery said.

Practice Considerations

The findings indicate that colonoscopy following an episode of diverticulitis for most patients is unlikely to provide benefit beyond routine colon cancer screening, the researchers wrote.

"Recommendations for colonoscopy after uncomplicated diverticulitis in patients current with CRC screening and without alarm symptoms should be reconsidered," they added.

However, they recommended follow-up colonoscopy to rule out missed CRC after diverticulitis when patients have a complication, symptoms of concern, or aren't current with screening.

"Finding colon cancer after diverticulitis is a real phenomenon and, to a large degree, avoidable in terms of bringing awareness and having clinics make a plan for follow-up colonoscopy, especially in an age where more patients are being treated without surgery," Daniel Feingold, MD, professor of surgery and chief of colorectal surgery at the Rutgers Robert Wood Johnson Medical School and Rutgers Cancer Institute of New Jersey, New Brunswick.

Feingold, who wasn't involved with this study, coauthored the American Society of Colon and Rectal Surgeons clinical practice guidelines for the treatment of left-sided colonic diverticulitis.

He and his colleagues recommended follow-up endoscopic evaluation if a colonoscopy hasn't been performed recently, especially for patients with complicated diverticulitis who may have CT findings with an abscess, "shouldering" or shelf-like appearance, bowel obstruction, and lymphadenopathy.

"This is important because patients who are ultimately found to have colon cancer may experience delays in diagnosis and treatment," Feingold said. "That's why, when working with patients in this situation, some of the first questions I always ask are: 'When was your last colonoscopy? And have you had one since the episode of diverticulitis?'"

The study was funded by grants from the National Institutes of Health. The authors declared no conflicts of interest. Feingold reported no relevant disclosures.

Carolyn Crist is a health and medical journalist who reports on the latest studies for Medscape, MDedge, and WebMD.