” One of the main differences between ulcerative colitis and Crohn’s disease are: Ulcerative colitis is limited to the colon while Crohn’s disease can occur anywhere between the mouth and the anus. In Crohn’s disease, there are healthy parts of the intestine mixed in between inflamed areas.  Ulcerative colitis and Crohn’s disease are the two main forms of inflammatory bowel diseases. They are both conditions characterized by chronic inflammation of the digestive tract. Although they share many similarities, there are key differences between the two diseases.”

UCLS Health (https://www.uclahealth.org/medical-services/gastro/ibd/what-ibd/ulcerative-colitis-vs-crohns-disease)