Can microscopic ileitis in patients with clinically suspected inflammatory bowel disease predict the future?

Background: The implication of microscopic ileitis finding in patients referred for ileocolonoscopy for clinically suspected inflammatory bowel disease (IBD) is not well defined, and its correlation with clinical outcome has not been fully studied. The current study aims to determine the prognostic yield of biopsies in this setting, and to evaluate the correlation of microscopic ileitis with long-term clinical outcome. Methods: We reviewed endoscopic reports of patients referred to our department for ileocolonoscopy in the years 2010-2016, as part of a diagnostic work-up for suspected IBD. Patients whose ileocolonoscopies proved normal were included, provided that terminal ileum biopsies had been performed. Accordingly, patients were divided into groups classified as normal (normal or reactive changes) and microscopic ileitis (inflammation or ileitis of any severity). Both groups were followed prospectively to determine clinical outcome. Results: A total of 439 patients met the inclusion criteria. Sixty-four (14.6%) showed inflammation on biopsy and were included in the microscopic ileitis group. Age range and gender figures did not differ significantly between the groups. Overall follow-up period was 6.1 ± 2.3 years. Patients in the microscopic ileitis group were significantly associated with Crohn's diagnosis during the follow-up period compared with the normal group (19% vs 2%, OR = 11.98, 95%CI = 4.48-32.01; p < 0.01). Patients with granuloma or moderate-severe ileitis on biopsy were significantly associated with Crohn's development (100% vs 11%; P < 0.01) compared with mild or nonspecific inflammation. Conclusion: The discovery of microscopic ileitis in clinically suspected IBD is associated with increased risk of future diagnosis of Crohn's disease.