Evaluation of remission in ulcerative colitis: Relationship between clinical, endoscopic, and histological markers as predictors of relapse

Introduction: In ulcerative colitis (UC), STRIDE-II consensus has established the long-term goal of achieving endoscopic remission (ER), which helps reduce inflammatory burden, prevent permanent intestinal damage, and improve patient's quality of life. However, achieving histological remission (HR) is also associated with a lower risk of experiencing outbreaks of inflammatory activity, the need for corticosteroids, hospitalizations, and the development of colorectal cancer. Objective: Evaluate the role of ER and HR in the development of inflammatory activity flares in patients who have achieved these long-term goals and are being followed in the Inflammatory Bowel Disease (IBD) Program. Material and methods: A retrospective study was conducted on patients with UC treated in the IBD Program at the Universidad de los Andes, between January 2021 and April 2023. Patients with ER (Mayo Endoscopic Index [MEI] 0) or endoscopic response (MEI 1), with at least one year of follow-up, were included. HR was defined using the Nancy (< 2), Geboes (< 2), and Robarts (< 3) indices. Inflammatory activity was assessed by a Partial Mayo Index (PMI) ≥ 2 and fecal calprotectin > 250 μg/g. Results: A total of 84 patients were included, 57.1% were women, with a median age of 37 years (IQR 31-45). During follow-up, 71 patients continued in the study, and 24 (31%) experienced inflammatory flares. In the MEI 0 group, the percentage of flares at 12 and 44 months was 15% and 53%, respectively, compared to 43% and 67% in the MEI 1 group (p = 0.0302). PMI and fecal calprotectin levels were significantly lower in MEI 0 than in MEI 1 (p < 0.001 and p < 0.05, respectively). Although the Nancy, Geboes, and Robarts indices showed significant differences between MEI 0 and MEI 1, none were associated with a lower risk of flares in the MEI 0 group. No cases of colorectal neoplasia or need for surgery were reported during follow-up. Conclusion: In this cohort, ER is a significant predictor of the development of inflammatory flares in patients with UC, while HR did not show a clear impact in this regard. Further studies are needed to clarify the role of HR as a therapeutic target in UC.