Ulcerative colitis is inflammation of the lower end of your digestive system, including your large bowel and rectum.
Common symptoms of ulcerative colitis include frequent diarrhoea (which may be bloody), stomach aches and needing to go to the toilet a lot.
It's not clear what causes ulcerative colitis. A possible cause is your immune system attacking your digestive system.
Ulcerative colitis is usually treated with medicines that reduce the inflammation in your digestive system. Surgery may be needed in severe cases.