Colitis is a term to describe an inflammation of the large intestine. In a differential diagnosis, it is further broken down into chronic and acute presentations. However, the term is often used to describe both a symptom of an unknown diagnosis, and the nature of a definitive diagnosis with a particular cause.
Colitis is a non-specific symptom and can not only point to many diseases, but many groups of conditions such as autoimmune, blood vessels, infection and even ideopathic.
If colitis progresses in severity with rapidity, it is called fulminant colitis, and narrows down the diagnostic probabilities. It is often accompanied by fever, diarrhea and anemia.
Colitis at Wikipedia