Ulcerative colitis is a chronic inflammatory bowel disease that affects the inner lining of the large intestine and rectum. Common symptoms include bloody diarrhea, abdominal pain, and urgency. Diagnosis involves endoscopy to examine the colon and detect changes like erosions and ulcerations. Treatment typically begins with medications like mesalamine to induce and maintain remission, while surgery may be required for severe cases or cancer prevention. Risk factors include family history and ethnicity, with symptoms and complications monitored through long-term management.