INTRODUCTION: Inflammatory bowel disease (IBD) is usually diagnosed when symptomatic. Prognosis and evolution of preclinical IBD is largely unknown. However, colorectal cancer screening programs (CRCSP) detect a subset of patients with IBD with no symptoms. The aim of this study was to describe the natural history of asymptomatic IBD diagnosed through CRCSP. METHODS: An observational, longitudinal, and retrospective study was performed at 22 centers in Catalonia between January 2010 and December 2019 including patients with asymptomatic IBD detected in the CRCSP. Demographic data and IBD characteristics, evolution, and treatment were recorded. Descriptive statistics and Kaplan-Meier analysis were used for the analysis. Data were given separately for IBD, Crohn's disease (CD), ulcerative colitis (UC), and IBD unclassified (IBDU). RESULTS: One hundred eighty-eight patients were included: 103 UC (54.8%), 60 CD (31.9%), and 25 IBDU (13.3%). Sixty-six (35.1%) were women, and the average age was 59.9 ± 5.9 years. Sixty-four patients (34.0%) developed symptoms after a median follow-up of 35.6 months. Diarrhea was the most frequent symptom for CD and IBDU (25.4% and 11.5%, respectively) and blood in stools for UC (21.4%). The median time to first symptom was 11.6 months. Treatment was prescribed in 135 patients (72.2%)
mesalazine was the most prescribed drug (123 patients
65.4%). Thirteen patients (6.9%) required biological treatment. None underwent surgery. DISCUSSION: Around one-third of asymptomatic patients with IBD developed symptoms after a medium follow-up of 3 years. Only 6.9% required biological treatment, and none required surgery. Overall, prognosis of asymptomatic IBD seems better.