Colitis is a general term used to describe any form of inflammation of the colon. Colitis typically causes pain and diarrhea, because the colon can no longer absorb water efficiently, leading to watery stools. Sometimes blood will also appear in the stool. There are many causes of colitis.
Ischemic Colitis
Colitis can be caused by disrupted blood flow, known as ischemia, to the colon. Ischemia can result from narrowing of the arteries that supply the colon, also known as arteriosclerosis or atherosclerosis. It can also occur if the intestine becomes twisted on itself, volvulus, or around an abdominal hernia.
Infectious Colitis
Infectious colitis is inflammation of the colon as the result of an infection, typically bacterial. The most common types of bacteria that infect the colon are salmonella, E. coli, shigella, and campylobacter. These bacteria are the most common culprits in food poisoning. Another bacteria, C. dificile, causes a condition known as pseudomembranous colitis. C. dificile can infect the colon after the patient has taken antibiotics.
Chemical Colitis
Some chemicals can irritate the tissue that lines the colon, the mucosa, causing inflammation. Harsh chemicals used for enemas sometimes cause this condition.
Inflammatory Bowel Disease
Another cause of colitis is one of the inflammatory bowel diseases: ulcerative colitis or Crohn's disease. Both diseases are auto-immune conditions, which means they are the result of an abnormally active immune system. In auto-immune diseases, the immune system attacks healthy tissue, such as the colon, causing inflammation.
Microscopic Colitis
Another auto-immune condition, microscopic colitis, also can cause colitis. This disorder causes collagen and white blood cells to build up in the walls of the colon. The condition is called microscopic colitis, because it usually can be diagnosed only by looking at a tissue sample underneath a microscope.
