The main reason for colonoscopy to only do the large bowel and not the small bowel is because colonoscopy can only look at part of the small bowel (terminal ileum). In addition, in addition to standing abdominal radiographs and small bowel imaging, abdominal CT and small colonoscopy can also be considered for small bowel disease. Colonoscopy is a common clinical test, which enters the rectum through the anus and into the large intestine to see if there are any lesions in the colon and large intestine. Since the instrument cannot enter the small intestine, only part of the small intestine can be observed. Clinical diseases that can be diagnosed through colonoscopy include colorectal polyps, ulcerative colitis, chronic colitis, and colon cancer. Before the colonoscopy, you should adjust your diet and good state of mind, and actively cooperate with the doctor to complete the examination. After the examination, take rest, try to take liquid food as the main, should also avoid strenuous exercise. If you want to observe whether the small intestine is diseased or not, you can consult the doctor for standing abdominal plain film, barium enema examination, pathology and histology examination. It is recommended to consult a regular hospital for colonoscopy, if the examination is accompanied by abdominal pain, persistent abdominal distension and other discomfort diagnosis and treatment, you need to consult a doctor in a timely manner.