Extensive evidence has underlined the importance of mucosal healing as a treatment aim for ulcerative colitis (UC). We aimed to assess differences in the incidence of clinical relapse at 12 months between UC patients with Mayo endoscopic scores (MES) 0 and 1.

This retrospective study included consecutive patients in corticosteroid-free remission between 2008 and 2013 and with follow-up of at least 1 year, with MES 0 or 1 in complete colonoscopy. Clinical relapse was defined as need for induction treatment, treatment escalation, hospitalization or surgery. A p value <0.05 was considered statistically significant.

The study included 138 patients, 72 (52.2%) female, with mean age of 49 (±14) years. Inflammatory activity was classified as MES 0 in 61 (44.2%) patients and MES 1 in 77 (55.8%) patients. Clinical relapse during follow-up was significantly more frequent in patients with MES 1 than MES 0 (27.3 vs 11.5%, p = 0.022), and in the multivariate analysis MES 1 was the only factor significantly associated with an increased risk of relapse (odds ratio 2.89, 95% confidence interval 1.14–7.36, p = 0.026). This association was encountered in the subgroup of patients with left-sided/extensive colitis (29.7 vs 11.1%, p = 0.049), but not proctitis (25.0 vs 12.0%, p = 0.202).

In patients with UC in corticosteroid-free remission, particularly those with left-sided colitis or extensive colitis, MES 1 was significantly associated with a 3-fold increased risk of relapse compared with endoscopic MES 0. Our results support the use of endoscopic MES 0 as the most suitable treatment endpoint to define mucosal healing in patients with UC.