Ulcerative colitis is an inflammatory bowel disease (IBD) that causes inflammation and ulcers (sores) in your digestive tract. Ulcerative colitis affects the innermost lining of your large intestine, also called the colon, and rectum. In most people, symptoms usually develop over time, rather than suddenly.

Ulcerative colitis – Symptoms and causes – Mayo Clinic

https://www.mayoclinic.org/diseases-conditions/ulcerative-colitis/symptoms-causes/syc-20353326

Listen to gastroenterologist William Faubion, M.D., walk through ulcerative colitis basics.