Prevalence and Clinical Features of Incidental Inflammatory Bowel Disease Identified During Screening and Surveillance Colonoscopy.

Background: Inflammatory bowel disease (IBD) can be detected in the absence of clinical symptoms.

Aims: To determine the prevalence of incidental IBD in patients undergoing screening colonoscopy and to explore its clinical features and long-term outcomes.

Methods: We conducted a retrospective cohort study that included all asymptomatic adults who underwent colonoscopy for colorectal cancer screening or polyp surveillance between 2009 and 2023 in a large health system. Incidental IBD was defined as endoscopic and histologic findings consistent with the disease in the absence of symptoms. Clinical characteristics and outcomes were collected.

Results: Among 40,573 patients who underwent colonoscopy, 60 were diagnosed with incidental IBD: 40 with Crohn's disease (CD), 10 with ulcerative colitis (UC), and 10 with IBD-unclassified (IBD-U). Mean age at diagnosis was 54.6 years for CD, 52.8 years for UC, and 55.7 years for IBD-U, with an overall female predominance (53%). Most CD patients had ileal involvement (98%) and inflammatory behavior (98%), and 60% of UC patients had extensive disease. After a mean follow-up period of 27.9 ± 34.7 months, 10 (16.7%) patients developed symptoms, and 5 (8.3%) initiated therapy, mostly after symptom onset. No hospitalizations or surgeries were reported.

Conclusion: The prevalence of incidental IBD detected during colorectal cancer screening is low (0.15%), with 20% of CD and 20% of UC cases progressing to symptomatic disease. Incidental IBD has a mild disease course with a low likelihood of progression to complications.