Colonoscopy can detect the presence of enteritis, such as chronic colitis, chronic proctitis, and inflammatory bowel disease, including ulcerative colitis and Crohn’s disease. For colonoscopy, not only can we know whether there are lesions in the intestinal mucosa, but also the severity of the lesions, and if necessary, we can also perform microscopic treatment or take the mucosal tissue for pathological biopsy to understand the specific nature of the lesions and whether there is cancer. Before colonoscopy, it is necessary to prepare the intestines, that is, to drink laxatives, and to consult with the gastroenterologist for the specific method of oral laxative administration.