Inflammation of the colon.ColonEncyclopedia Entry for Colitis :Colitis. Most of the time, the cause of colitis is unknown. Causes of colitis include: Infections caused by a virus or a parasite Food poisoning due to bacteria Crohn disease Lack of blood flow (ischemic colitis) Past radiation to the large bowel (radiation stricture) Necrotizing enterocolitis in newborns Pseudomembranous colitis caused by Clostridia difficile infection.Symptoms can include: Abdominal pain and bloating that may be constant or come and go Bloody stools Constant urge to have a bowel movement (tenesmus) Dehydration Diarrhea Fever.The health care provider will perform a physical exam. You will also be asked questions about your symptoms, such as: How long have you had the symptoms? How severe is your pain? How often do you have pain and how long does it last? How often do you have diarrhea? Have you been traveling? Have you been taking antibiotics recently? The provider can diagnose colitis by inserting a flexible tube into the rectum (flexible sigmoidoscopy or colonoscopy ) and looking at certain areas of the colon. You may have biopsies taken during this exam. Biopsies may show changes related to inflammation. This can help determine the cause of colitis. Other studies that can identify colitis include: CT scan of the abdomen MRI of the abdomen Barium enema Stool culture Stool examination for ova and parasites.Your treatment will depend on the cause of the disease.The outlook will vary, depending on the cause of the problem.Complications may include: Bleeding with bowel movements Perforation of the colon Toxic megacolon Sore (ulceration).Call your provider if you have symptoms such as: Abdominal pain that does not get better Blood in the stool or stools that look black Diarrhea or vomiting that does not go away Swollen abdomen.Ulcerative colitis Ulcerative colitis Large intestine Large intestine Large intestine (colon) Large intestine (colon) Crohn disease, X-ray Crohn disease, x-ray.Osterman MT, Lichtenstein GR. Ulcerative colitis.