The examination of early stage bowel cancer is as follows: 1. see whether there is abdominal pain, blood in stool, anemia or unexplained wasting symptoms; 2. see whether there is local thickening of intestinal canal in CT examination; 3. see whether the stool occult blood test is positive. If it is rectal cancer, there can be blood in stool, incomplete stool and feeling of urgency, especially if there is a family history of colorectal cancer, regular colonoscopy is needed, generally you can do colonoscopy once a year to exclude the possibility of colorectal cancer, and colonoscopy is the only basis to confirm the diagnosis of early bowel cancer. Before that, screening can be done by tumor markers, such as carcinoembryonic antigen, etc. It is worth pointing out that tumor markers can only play a suggestive diagnostic role, but not a decisive diagnosis, and the decisive diagnosis or confirmation needs to rely on the pathology obtained by colonoscopy.