The main function of the colon is to help shape the stool, which is caused by ulcerative colitis, rectal polyps, and rectal tumors. The main function of the colon is to help shape the stool, and when the ulcerated surface of the colon mucosa appears, the function of the colon will be affected, and not only will the stool be unshaped, but the number of bowel movements will also increase. Patients with gastroenteritis also have abdominal pain and diarrhea, and some of them have mucus-purulent stools. The presence of polyps on the mucosa of the rectum can cause some irritation to the colon, and then the patient will have a feeling of urgency and heaviness. The rectum is often stimulated by the polyps, so it will produce the urge to defecate, but the amount of stool stored in the rectum is not particularly large, and not much is defecated each time. Rectal tumor is a malignant disease, which not only affects the function of rectum, but also causes irritation to the mucous membrane of rectum, so it will be accompanied by more frequent bowel movements and less amount of stool.