ENDOSCOPIC ASSESSMENT AND MONITORING OF DISEASE ACTIVITY IN ULCERATIVE COLITIS

Abstract

In ulcerative colitis (UC), mucosal healing (MH) is a central therapeutic target strongly associated with favorable long-term outcomes. Endoscopy remains the most direct and reliable method for evaluating MH, and endoscopic activity indices have progressed from early systems, including the Baron index and Matts grading system, to more standardized tools such as the Mayo endoscopic subscore (MES) and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS). Although MES is widely adopted because of its simplicity, the clinical distinction between MES 0 and 1 remains controversial. UCEIS was developed to enable more precise evaluation of inflammatory severity; however, its routine use in clinical practice remains limited. More recently, the concept of deep remission, defined as the combination of endoscopic MH and histological remission, has gained increasing attention. Accumulating evidence suggests that sustained endoscopic and histological remission over time, rather than a single cross-sectional evaluation, is critical for predicting disease relapse. Accordingly, treatment response in UC should be assessed longitudinally as a “line,” rather than as a single “point.” Advances in next-generation endoscopic technologies, including high-definition and image-enhanced endoscopy, endocytoscopy, and confocal laser endomicroscopy, as well as the development of artificial intelligence (AI)-based automated scoring systems, have improved diagnostic precision. These innovations reduce interobserver variability and enhance differentiation between MES 0 and 1 in routine clinical settings. Furthermore, integrated monitoring strategies that combine AI-assisted endoscopic assessment with noninvasive biomarkers, such as fecal calprotectin and serum leucine-rich α2-glycoprotein, are expected to play an increasingly important role. This review summarizes the evolution of endoscopic activity assessment in UC, the definition and clinical significance of mucosal healing, its association with histological remission, and the emerging role of AI and next-generation technologies in disease monitoring. It also discusses the future role of endoscopy in personalized UC management.