When bowel cancer is suspected, the following examinations can be performed: 1. Stool routine, mainly checking whether the stool is positive for occult blood. Many patients with early stage bowel cancer have chronic blood loss but do not show bloody stool clinically, i.e. normal stool with naked eye but bleeding inside, so positive occult blood can indicate the possibility of lesions in the digestive tract; 2. tumor markers, elevated tumor markers indicate the possibility of lesions. If tumor markers are normal, it does not mean there is no possibility of intestinal cancer; 3. Anal diagnosis, 70% of colorectal cancers occur in the rectum, and 70% of rectal cancers are in the lower rectum, which is about 7cm below the anus. The length of a finger is also about 7cm, so the simple and practical anal examination can also be used to understand whether there is malignant change in the lower rectum; 4.colonoscopy, many colorectal cancers may have multi-source tumors, and cancer in the rectum, the right half of the colon may also exist or exist in other precancerous lesions, such as intestinal polyps. Through colonoscopy, we can understand the lesions of the whole colon and obtain pathological examination at the same time.