This differs from ulcerative colitis , which is limited to the colon and rectum. Microscopic colitis , which includes lymphocytic and collagenous colitis , also can cause ongoing watery diarrhea, but it is different from ulcerative colitis . Colitis is inflammation in your colon, which is the main part of your large intestine. Your colon is the last leg of the journey your food takes through your digestive system. Inflammation makes the tissues in your colon swell and cause discomfort. This can affect the way the journey ends, causing pain, diarrhea and, sometimes, blood in your poop. Colitis can also affect your quality of life and make it difficult to do your normal activities. Colitis is inflammation of the large intestine that can be acute or chronic. Learn about the different types of colitis , such as ulcerative colitis , Crohn's disease, infectious colitis and more, and how they are diagnosed and treated. Most of the time, the cause of colitis is not known. Causes of colitis include: Infections caused by a virus or a parasite Food poisoning due to bacteria Crohn disease Ulcerative colitis Lack of blood flow to the colon (ischemic colitis ) Past radiation to the colon (radiation colitis and strictures) Necrotizing enterocolitis in newborns Pseudomembranous colitis caused by Clostridium difficile infection (now called Clostridiodes difficile)
