Ulcerative colitis is an inflammatory disease of the colon of unknown causes characterized by bloody diarrhea, a tendency to remissions and exacerbations and involvement mainly of the left colon. It is primarily a disease of adolescents and young adults but may have its onset in any age group.
The pathologic process is that of acute nonspecific inflammation in the colon, particularly the rectosigmoid area, with multiple irregular superficial ulcerations.
Repeated episodes lead to thickening of the wall with scar tissue, and the proliferative changes in the epithelium may lead to polypoid structures. Pseudopolyps are usually indicative of severe ulceration. The cause is not known; it may be multiple.
The disease is usually called "dysentery," "damp-heat dysentery" or "bloody stool" in traditional Chinese medicine, and is thought to be caused by internal stasis of dampness and heart. The pathologic changes in which damp and heat pathogens stay deeply in the body. Thereby various manifestations of gastrosplenic dysfunctions may occur.
Sigmoidoscopic changes are present in over 95% of cases and vary from mucosal hyperemia, petechiae and minimal granularity in mild cases to ulceration and polypoid changes in severe cases. The mucosa, even when it appears grossly normal,is almost invariably friable when wiped with a cotton sponge. Colonoscopic examination may prove useful in defining the extent of ulcerative colitis and in permitting biopsy of radiographically suspect regions.