Infectious disease examination, electrocardiogram and bowel preparation are performed before colonoscopy. 1. Infectious disease examination: infectious diseases are usually transmitted through blood and respiratory tract. Enteroscopy is an invasive examination, and infectious diseases, such as hepatitis B, hepatitis C, AIDS, syphilis, etc., should be excluded from the intestinal examination. 2. Electrocardiography: During colonoscopy, there is a possibility that heart disease may be induced, such as heart attack, cardiac arrest, etc. Therefore, in order to exclude heart disease, you can check through electrocardiography and cardiac ultrasound. 3. Intestinal preparation: In colonoscopy, you need to clean the intestines, you can’t eat 8 hours before the examination, you need to take intestinal cleansing agents, drink more water to discharge intestinal feces, fecal sludge and other substances, and the feces to be discharged are watery or yellowish, you can carry out the colonoscopy. Enteroscopy can detect intestinal polyps, intestinal tumors and other lesions, and is a commonly used means of examination nowadays. It is recommended that the examinee follow the doctor’s instructions and perform the intestinal examination in an orderly manner.