1, abdominal distension, abdominal pain The cause is due to intestinal dysfunction, or intestinal obstruction. The location is mostly concentrated in the middle and lower abdomen, mostly hidden pain or distension, and there is a tendency of gradual aggravation. 2.Blood in stool Because the lesion is closer to the anus, the blood color is mostly bright red or dark red, and often the blood and stool are separated, and only when the bleeding volume is larger, the stool is brownish red and jam-like. There are such in patients with right hemi colon cancer, and blood in stool visible to the naked eye accounts for 36. 5%. This also belongs to the early symptoms of colorectal cancer. 3.Anemia When the long-term chronic blood loss exceeds the compensatory function of hematopoiesis, the patient will have anemia, which is an early symptom of colorectal cancer. Tumor obstruction, when the tumor grows to a considerable size or infiltrates the muscle layer of intestinal wall, it can cause narrowing of intestinal canal, small intestinal lumen and obstruction of intestinal content. 4.Changes in stool habits and traits Patients with rectal cancer may have more frequent stools, but not much stool each time, or even no stool at all, only some mucus and blood are discharged, and there is a 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.