Colorectal cancer is one of the gastrointestinal tumors with high incidence in China, and its incidence rate is showing a trend of youthfulness and increasing year by year. Colonoscopy is an effective means to screen for bowel cancer, which can detect early cancer or precancerous lesions, and is also a common test for bowel cancer patients in the treatment. Many people are afraid of colonoscopy, but in fact, it is not necessary because “painless” colonoscopy has long been popular. A successful colonoscopy requires a clear surface of the colon mucosa, otherwise it will prolong the operation time, increase the risk of complications and the possibility of missed lesions. Therefore, intestinal cleanliness is a prerequisite for colonoscopy, how to prepare to make the cleanliness higher? Patients who are scheduled for colonoscopy are recommended to avoid foods with high fiber content (fruits, vegetables, whole grains) from 3 days in advance, and to choose low residue meals (porridge, rice, noodles, bread, steamed eggs, egg broth, tofu, chopped and boiled lean meat or fish). Choose clear liquid (rice soup, soybean milk, lotus root powder, fruit juice, vegetable juice) for dinner 1 day before the examination, not milk! Second, what time to start not to eat 6-8 hours before the colonoscopy prohibited to eat through the mouth! 2 hours before the examination is prohibited to drink any liquid (including water Oh)! Third, oral laxatives to cleanse the intestines The most widely used oral intestinal cleansers include compound polyethylene glycol electrolyte dispersion, mannitol injection two. You can choose to give them orally 1 hour after dinner (around 8:00 pm) on the day before the examination. If the examination is scheduled in the afternoon, take them orally after waking up earlier on the day of the examination, at least 6-8 hours earlier than the examination time. Take it orally at a rate of 1-1.5L per hour, and you will feel bloated almost one hour later. If you feel that the bloating is unbearable or abdominal pain occurs, you can temporarily slow down or suspend taking it, and continue taking it after the symptoms disappear. If you feel that the taste is not good you can cool the warm water or use a straw to drink may be easier to take. Most people will have “clear” stools after 3-4 bowel movements, but constipated patients may need more bowel movements to achieve their goal. Poor bowel preparation may not be conducive to a colonoscopy and a more comprehensive bowel cleanse, such as a cleansing enema, will have to be attempted. Therefore, try to follow the instructions for preparation as closely as possible and aim for one visit. If bowel preparation is still poor despite following the instructions, it is recommended to eat a clear liquid 2 days in advance, consider taking laxatives for 2 consecutive days, and schedule the colonoscopy for the morning. Never drink too much too fast to meet the examination criteria as soon as possible, or add and change medication on your own! The difference between painless colonoscopy, including anesthesia colonoscopy and sedation colonoscopy, is that one uses anesthetic drugs under the monitoring of anesthesiologists, and the other uses sedative drugs. While waiting for the examination, the physician will open the intravenous access of the patient, and when it is the patient’s turn to be examined, the physician will inject the sedative from the intravenous access drip into the body, which may cause local pain, but there is no need to panic, it will soon be relieved, and you can fall asleep after closing your eyes and breathing deeply for a few minutes. The physician will monitor the heart rate, oxygen saturation, blood pressure and other parameters to ensure the safety of the examinee. After the examination, the patient will wake up within a few minutes after the sedative medication is stopped. Therefore, the doctor requires a family member to accompany the patient and does not recommend driving to the doctor on the same day to avoid unnecessary accidents. In addition, most of the examiners will feel bloating, abdominal pain, or a little stool when exhausting, which is normal after colonoscopy and will gradually subside after 2 hours, so there is no need to be overly nervous. V. Interpretation of results Usually if no biopsy is performed, the examination report will be available on the same day. If the doctor finds a foreign body growth during the examination, he or she will choose to remove the biopsy, and the pathology report of the biopsy will usually come out after 3-5 working days, so when you encounter this situation, please wait patiently for the pathology report, and then go to the specialist after the pathology report comes out. VI. Who needs regular colonoscopy According to the recommendations in the 2017 NCCN guidelines, stage I, II, and III patients, colonoscopy is recommended in the first, third, and fifth years after surgery, during which annual review is recommended if adenomas, villous polyps, polyps >1 cm, or high-grade intraepithelial neoplasia are found. If you have an immediate family member who developed bowel cancer before the age of 50, and you do not have oncological disease, it is recommended to have a colonoscopy every 6 years. If you have recurrent blood in the stool, constipation, or loss of weight, a colonoscopy can help you find the cause of the disease.