BACKGROUND AND AIM: Peyer's patches (PPs) play a major role in intestinal 
mucosal immunity; however, their role in ulcerative colitis (UC) is not well 
investigated. We evaluated endoscopic features of PPs on narrow-band imaging 
with magnifying endoscopy (NBI-ME) and investigated their association with 
clinical factors.
METHODS: We prospectively recruited 105 patients with UC, 18 with Crohn's 
disease, 16 with disease control, and 33 healthy control subjects at three 
institutions from 2014 to 2017. NBI-ME images of the villi of PPs were evaluated 
according to the Villi Index, and patients were divided into the Villi Index low 
(L) and high (H) types. The 1-year sustained clinical remission rate was 
evaluated between L-type and H-type PPs in patients with UC.
RESULTS: The proportions of patients with H-type PPs were significantly higher 
among UC, Crohn's disease, and disease control patients than among healthy 
control patients (P = 0.0125, 0.018, 0.0007). In UC, age, gender, endoscopic 
score, and extent of disease involvement were not significantly different 
between L-type and H-type PPs, whereas the sustained clinical remission rate was 
significantly higher in L-type PPs than in H-type PPs (88% [57/65] vs 65% 
[17/26], P = 0.019). Multivariate analysis revealed that the L type of PPs was a 
significant factor for sustained clinical remission (odds ratio 3.8, 95% 
confidence interval 1.1-12.9, P = 0.033).
CONCLUSIONS: Patients with UC showed endoscopic alterations in PPs on NBI-ME, 
and highly altered appearance of PPs can be associated with a high risk of 
clinical relapse in patients with UC.