The entire process of having a colonoscopy is a method of examining the entire colon and rectum by looking at the entire colon and rectum through an electronic colonoscope that is passed through the anus into the intestines. Generally, colonoscopy can reach the ileum, the opening of the appendix. For some patients, the colonoscope can access the end of the ileum to view part of the small bowel mucosa. Because colonoscopy allows direct access to the bowel to observe lesions, colonoscopy is a more visual and accurate method than others. Usually, before colonoscopy, patients need to start fasting after 10:00 p.m. the night before the examination to clean out the intestines in advance. Colonoscopy can be performed when the stool is watery, clear or yellow in color and there is no obvious substantial stool. If patients need to do colonoscopy, it is recommended to consult the doctor in time and perform colonoscopy under the guidance of professional doctors to avoid adverse consequences.