Ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease of unknown aetiology affecting the colon and rectum. Multiple factors, such as genetic background, environmental and luminal factors, and mucosal immune dysregulation, have been suggested to contribute to UC pathogenesis. UC has evolved into a global burden given its high incidence in developed countries and the substantial increase in incidence in developing countries. An improved understanding of the mechanisms underlying UC has led to the emergence of new treatments. Since the early 2000s, anti-tumour necrosis factor (TNF) treatment has significantly improved treatment outcomes. Advances in medical treatments have enabled a paradigm shift in treatment goals from symptomatic relief to endoscopic and histological healing to achieve better long-term outcomes and, consequently, diagnostic modalities have also been improved to monitor disease activity more tightly. Despite these improvements in patient care, a substantial proportion of patients, for example, those who are refractory to medical treatment or those who develop colitis-associated colorectal dysplasia or cancer, still require restorative proctocolectomy. The development of novel drugs and improvement of the treatment strategy by implementing personalized medicine are warranted to achieve optimal disease control. However, delineating the aetiology of UC is necessary to ultimately achieve disease cure. Ulcerative colitis is a chronic inflammatory bowel disease affecting the rectum and the colon. This Primer describes the epidemiology, the current understanding of ulcerative colitis pathophysiology and its diagnosis. In addition, Hibi and colleagues highlight the current and emerging therapeutic strategies and discuss the most pressing questions in the field.