Prevalence and Progression of Incidental Terminal Ileitis on Non-diagnostic Colonoscopy: A Systematic Review and Meta-analysis

Background: Incidentally diagnosed terminal ileitis [IDTI] has been reported among asymptomatic persons undergoing non-diagnostic colonoscopy. The purpose of our study was to determine the prevalence and long-term outcomes of asymptomatic terminal ileitis. Methods: We performed a systematic review using three biomedical databases [Medline, Embase, and Web of Science] and relevant scientific meeting abstracts. We identified observational studies that reported the prevalence of IDTI in adults undergoing screening or polyp surveillance colonoscopy and/or the long-term outcomes of such lesions. A random-effects meta-analysis was conducted to determine the pooled prevalence rate of IDTI. The progression of IDTI to overt Crohn's disease [CD] was also described. Results: Of 2388 eligible studies, 1784 were screened after excluding duplicates, 84 were reviewed in full text, and 14 studies were eligible for inclusion. Seven studies reported the prevalence of IDTI in 44 398 persons undergoing non-diagnostic colonoscopy, six studies reported follow-up data, and one study reported both types of data. The pooled prevalence rate of IDTI was 1.6% (95% confidence interval [CI] 0.1-21.8%) with significant heterogeneity [I2=99.7]. Among patients who had undergone non-diagnostic colonoscopy and had follow-up data [range 13-84 months reported in five studies], progression to overt CD was rare. Conclusions: IDTI is not uncommon on non-diagnostic colonoscopies. Based on limited data, the rate of its progression to overt CD seems low, and watchful waiting is likely a reasonable strategy. Further long-term follow-up studies are needed to inform the natural history of incidental terminal ileitis, factors that predict progression to CD, and therapeutic implications.