Prognostic Effect of MES 1 Inflammatory Extent on Remission Maintenance in Ulcerative Colitis

Ulcerative colitis (UC) is characterized by continuous inflammation extending from the rectum. Even mild inflammation can present prognostic implications when the disease is extensive. Mayo Endoscopic Score (MES) 1 represents increased risk of relapse, hospitalization, and treatment modification, but it is based solely on inflammation intensity, incorporating consideration of neither extent nor localization.

Patients with UC in clinical remission with MES 0 or 1 at the initial endoscopic assessment after induction therapy were enrolled retrospectively and were followed for 2 years. Effects of the inflammation extent on remission maintenance were analyzed retrospectively for patients evaluated as MES 1. We investigated whether all MES 1 inflammation should be treated equally.

For the 301 included patients, the remission maintenance rate was significantly higher in the MES 0 group than in the MES 1 group (88.9% vs. 67.3%, p < 0.001). Moreover, MES 1 patients with 1-2 inflamed segments had higher remission maintenance rates than those with 3-6 inflamed segments (78.4% vs. 45.6%, p < 0.001). A significantly higher remission maintenance rate was found for the MES 0 group than for the MES 1 group with 1-2 inflamed segments (88.9% vs. 78.4%, p = 0.037). No significant difference was found between rectal and non-rectal involvement (80.7% vs. 76.5%, p = 0.685).

The remission maintenance rate decreases as the extent of MES 1 inflammation increases in patients in remission. Even mild but extensive inflammation may increase the risk of relapse. Treatment strategies should incorporate consideration of the inflammation extent.