Isolated Acute Terminal Ileitis Without Preexisting Inflammatory Bowel Disease Rarely Progresses to Crohn’s Disease

Background: Isolated acute terminal ileitis without chronic features of inflammation poses a diagnostic challenge. Few studies have investigated the clinical significance of this entity in patients without history of inflammatory bowel disease. Aims: We sought to elucidate the long-term prognosis of patients with isolated acute terminal ileitis, its rate of progression to Crohn’s disease, and the factors associated with terminal ileitis development to Crohn’s disease. Methods: Retrospective review of clinical, endoscopic, and radiographic records was performed on 108 patients with histologic evidence of isolated acute terminal ileitis on terminal ileal biopsies obtained by diagnostic ileocolonoscopy performed between January 1, 2002, and December 31, 2014, at the Mayo Clinic. Statistical analysis was performed with Student’s t test and Fisher’s exact test to identify the factors associated with the progression of isolated acute terminal ileitis to Crohn’s disease. Results: The median follow-up time across 108 patients was 54.7 months (interquartile range 32.0–89.0 months). Five patients (4.6%) developed Crohn’s disease after a median of 32.3 months (7.5–43.2 months). The presence of narrowing/stricturing (p = 0.03) on abdominal cross-sectional imaging at the time of terminal ileitis diagnosis was correlated with eventual Crohn’s disease development. No significant correlation was found with clinical symptoms, endoscopic features, laboratory testing, NSAID use, smoking history, or family history of inflammatory bowel disease. Conclusions: Isolated acute terminal ileitis discovered on diagnostic ileocolonoscopy rarely develops to Crohn’s disease. Presence of stricturing/narrowing on cross-sectional imaging may predict eventual Crohn’s disease development.