Histological Risk Factors to Predict Clinical Relapse in Ulcerative Colitis With Endoscopically Normal Mucosa

Background and Aims The current goal of treatment for ulcerative colitis [UC] is endoscopic and ultimately histological mucosal healing. However, there is no consensus on the definition of histological mucosal healing. We evaluated histological risk factors for clinical relapse in UC patients with endoscopically normal mucosa to focus on the importance of histological evaluation. Methods Patients with UC who underwent colonoscopy confirming Mayo endoscopic subscore [MES] ≤ 1 with biopsies were enrolled into this retrospective cohort. Three expert pathologists evaluated the presence or absence of chronic inflammatory cell infiltrate, breaches in the surface epithelium, crypt abscesses, mucin depletion, crypt architectural irregularities and basal plasmacytosis. Clinical relapse was defined as partial Mayo score ≥ 3 or modification of induction treatment. Prediction models of clinical relapse were generated, especially in patients with MES 0. Results A total of 194 UC patients were enrolled. Histological abnormalities existed more frequently in patients with MES 1 than those with MES 0, while the vast majority of patients still possessed at least one abnormality. There was no significant difference in time to relapse between MES 0 and 1. Crypt architectural irregularities and mucin depletion were associated with time to relapse in patients with MES ≤ 1. In patients with MES 0, the presence of mucin depletion was the only factor significantly and independently associated with the risk of relapse (hazard ratio, 2.18 [1.16-5.82]; p = 0.03). Conclusions Mucin depletion was shown to be a histological risk factor for clinical relapse in UC patients with MES 0.