Crohn’s Disease, or Ulcerative colitis (UC), is a disease marked by inflammation of the lining of the colon and rectum, together known as the large intestine. This inflammation causes irritation in the lining of the large intestine, which leads to the symptoms of UC. Though UC always affects the lowest part of the large intestine (the rectum), in some patients it can be present throughout the entire colon. UC belongs to a group of diseases called inflammatory bowel diseases, which also includes Crohn’s disease (CD). Though it was once thought that UC and CD were two different diseases, as many as 10% of patients may have features of both diseases, and this is called indeterminate colitis. It is important to note that inflammatory bowel disease (IBD) is different from irritable bowel syndrome (IBS).