This article reviews the current understanding of the pathophysiology, diagnosis, and treatment of ulcerative colitis to date. The authors also compare ulcerative colitis with Crohn's disease. The following topics are discussed:

• Pathogenesis
   o Epidemiologic Features
   o Genetic Features
   o Microbiologic Features
   o Mucosal Immune Response
   o Epithelial Cells and Autoimmunity

• Clinical manifestations
   o Symptoms, Clinical Course, and Assessment of Disease Activity
   o Complications

• Diagnosis
   o Endoscopic Studies
   o Histologic Evaluation
   o Laboratory Tests

• Therapy
   o Medical Therapy
   o Surgical Treatment

• Future challenges and novel therapies