Colitis, Inflammation Of The Colon, may be restricted to some one part of the colon, as the cecum, sigmoid flexure, etc., or involve all portions. It is generally due to the retention of large masses of hard feces, or to bacterial infections; as tuberculosis and syphilis. Certain poisons, particularly the metallic, can set up severe inflammations; can also be due to products elaborated within the body, as in chronic nephritis. The mucosa is much thickened and there is a marked secretion of mucus which is mixed with exfoliated epithelium, leukocytes and red cells. The mucosa frequently ulcerates and may become covered by a pseudo-membranous substance made up of desquamated epithelium and mucus. The walls of the intestine are frequently infiltrated with pus cells and fibrin. This pseudo-membrane may be passed from the rectum, in pieces or as a cast {mucous colitis).