If the colonoscopy is performed by professionals in a regular hospital, there are usually no sequelae, and patients may only experience abdominal pain, bloating and other discomfort. If the operation is improper, it may cause intestinal bleeding, intestinal perforation, anesthesia accidents, etc., but the probability of occurrence is generally low. Common sequelae and treatment 1, intestinal bleeding: can be caused by the colonoscope contact with the diseased intestinal mucosa, or extraction of intestinal tissues caused by bleeding, usually can recover on its own after the end of the examination. If abdominal pain and blood in the stool occur after the examination, prompt medical attention is required. 2. Intestinal perforation: It can be caused by intestinal perforation mainly due to improper operation and rupture of the thinning intestinal canal caused by intestinal lesions. Before colonoscopy, the doctor needs to understand the patient’s condition and make the patient take the correct way for examination; 3, anesthesia accident: some patients may choose painless colonoscopy because they cannot tolerate pain. If patients have allergy and other symptoms to the intravenous infusion of anesthetic drugs, anesthesia accidents can occur. Therefore, patients need to inform the doctor of their own situation in advance to prevent accidents. Preparation before the examination also requires strict bowel preparation before the colonoscopy to meet the standard of intestinal cleanliness and to improve the accuracy of the examination. Usually, three days before the examination, patients need to stop taking iron, aspirin-like drugs or other anticoagulants and eat a semi-liquid, low residue, low fiber diet such as rice porridge and egg custard. A liquid diet, such as rice soup or broth, should be chosen for dinner the day before the test. On the day of the examination, you should abstain from drinking and eating to prevent asphyxia caused by regurgitation of gastric contents into the trachea during anesthesia.