In general, doing colonoscopy is not harmful to the body. However, it may cause intestinal bleeding, perforation or even induce myocardial infarction and other diseases for some special people such as patients with intestinal adhesions, intestinal polyps, and serious cardiovascular diseases such as heart failure. 1. Intestinal bleeding: If the patients themselves have intestinal polyps or blood system diseases (such as abnormal coagulation function or taking anticoagulant drugs, etc.), it may cause intestinal bleeding and other complications when doing colonoscopy or performing biopsy. 2. Intestinal perforation: if the patient has intestinal adhesions or has had abdominal surgery, etc., there is a possibility of intestinal perforation when doing colonoscopy. The integrity of the intestinal wall is damaged and the intestinal contents overflow into the peritoneal cavity, which can cause localized or diffuse peritonitis, with severe abdominal pain, distension, abdominal muscle tension and other signs and symptoms, and in severe cases, can also lead to infectious shock. 3. Cardiovascular and cerebrovascular complications: such as myocardial infarction, cerebral infarction, cerebral hemorrhage and so on. If the patient himself suffers from cardiovascular and cerebrovascular diseases, such as myocardial ischemia, etc., in the process of doing colonoscopy, due to mechanical stimulation caused by intestinal discomfort, such as pain, distension, etc., it may cause an increase in the cardiac load, myocardial infarction and other complications.