1. Gradually increasing abdominal distension and abdominal pain. The cause is due to intestinal dysfunction, or intestinal obstruction. The area is mostly concentrated in the middle and lower abdomen, mostly hidden pain or distension, and there is a tendency of gradual aggravation. 2. Intermittent blood in the stool. Because the lesion is closer to the anus, the blood is mostly bright red or dark red, and is often separated from the blood and stool. Only when the amount of bleeding is high, the stool will be brownish red and jam-like. Blood in the stool visible to the naked eye accounts for 36.5% of patients with right hemicolectasis. 3.Anemia. When the long-term chronic blood loss exceeds the compensatory function of hematopoiesis of the body, the patient may show anemia, and the anemia will be aggravated as the disease progresses. 4.Changes in bowel habits and stool characteristics. Patients with rectal cancer may have more stools, but not much stool or even no stool at all, just some mucus and blood, and the feeling of incomplete defecation. The change of stool habit and frequency, as well as constipation or unexplained diarrhea may occur only when the colorectal tumor is relatively large and has erosion, ulcer or infection. If the cancer grows prominently into the rectal cavity, resulting in relative narrowing of the intestinal cavity, the excreted stool often becomes thin, deformed, and may be flat, and sometimes some blood is attached to the deformed stool.