Nodular lymphoid hyperplasia of terminal ileum: how to avoid overdiagnosis of Crohn's terminal ileitis in MR enterography?

PURPOSE To investigate the magnetic resonance enterography (MRE) characteristics of nodular lymphoid hyperplasia (NLH) and Crohn's terminal ileitis (CTI). METHODS Of 1552 MREs from November 2011 to July 2018, 61 individuals with biopsy-proven NLH (n = 24) and CTI (n = 37, 27 with active CTI) were selected based on the inclusion criteria. NLH cases were also followed up for median (range) of 40 (21-61) months. Two board-certified radiologists, blind to clinical data and diagnosis, reviewed MRE in consensus. Conventional, morphological, enhancement, and diffusion parameters were assessed. Mann-Whitney, χ2, and logistic regression analyses were conducted. RESULTS No NLH patient developed inflammatory bowel disease or lymphoproliferative disorders during the follow-up. Serosal surface irregularity (65% vs. 8%), pseudo-diverticula (27% vs. 0), and mesenteric fat involvement (38% vs. 4%) were more frequent in CTI than NLH (p < 0.01), while mucosal nodularity was more prevalent in NLH (71%) than CTI (19%) (p < 0.001). The upstream luminal diameter (15.0 vs. 12.5 mm, p = 0.015) and mural thickness (6.0 vs. 4.0 mm, p < 0.001) of the terminal ileum showed higher values in CTI than NLH. CONCLUSIONS Unlike enhancement and diffusion parameters, morphological features (mucosal nodularity, serosal surface irregularity, and mesenteric fat involvement) could distinguish NLH from CTI regardless of CTI activity.