A small colonoscopy needs to be performed twice, once from the anal side and once from the oral side, and then intersects in the middle of the small intestine in order to completely visualize the 5-7 meter long small intestine. This is because the small intestine is very long and the lumen is thin and soft. It is difficult to fully examine the small intestine if it is entered only from the mouth or anal side. Therefore, a single small colonoscopy needs to be done twice from the mouth side and the anal side, intersecting in the middle of the small intestine, which makes it easy to maneuver and to complete the examination. Small colonoscopy can observe localized lesions, take biopsies, and perform operations such as removal of polyps, both for diagnosis and appropriate treatment. The operation of small colonoscopy is difficult and time-consuming, which requires high physical and mental strength of medical workers. If a patient has gastrointestinal symptoms, he or she should consult a doctor promptly. It is up to the doctor to determine whether a small colonoscopy is necessary.