Characteristics and Progression of Preclinical Inflammatory Bowel Disease.

Background & Aims: Inflammatory bowel disease (IBD) is a chronic disease usually diagnosed after the appearance of gastrointestinal symptoms. Little is known about IBD progression during its early and even preclinical phases. We aimed to determine the number of new incidental diagnoses of IBD in an older population, and evaluate disease progression from its early stages.

Methods: We performed a retrospective analysis of 31,005 colonoscopies performed during colorectal cancer screening of patients with positive results from fecal immunochemical tests, at 11 centers in the Basque Country (Spain) from 2009 through 2014. We collected clinical and laboratory data from all asymptomatic individuals suspected to have IBD during screening colonoscopies, with histologic confirmation.

Results: Colonoscopy screening led to 79 new diagnoses of ulcerative colitis, 24 of Crohn's disease, and 7 of unclassified colitis (average patient age, 57 y; interquartile range, 52-62 y; 57% male). Eleven patients had symptoms before colonoscopy and were excluded from the analysis. Among those patients who were asymptomatic at diagnosis, 36% developed symptoms after a follow-up period of 25 months (interquartile range, 10.5-42 mo), mostly rectal bleeding and diarrhea. Treatment was prescribed for 81 patients (88%), and 2 cases required surgery.

Conclusions: We analyzed data from a large cohort of patients with IBD diagnosed at early or even preclinical stages, from an older population. New incidental diagnoses of IBD were made in 0.35% of individuals undergoing a population-based screening colonoscopy-most were classified as ulcerative colitis. Approximately one third of patients developed symptoms during the follow-up period.