Colonoscopy has an irreplaceable role in detecting colorectal polyps and colorectal cancer. If the intestine is not well prepared for colonoscopy, the residue in the intestine will affect the doctor’s judgment, and some patients even need to prepare again and undergo the examination twice. The adequacy of bowel preparation is directly related to the detection rate of polyps, and the significance of colonoscopy is greatly reduced if the bowel is not well prepared. The following four pictures represent, from left to right, what is seen under colonoscopy when the bowel preparation is very good, good, bad and very poor. It is internationally recommended that patients undergoing colonoscopy for the first time should be re-examined within 1 year if their bowel preparation is not adequate. Therefore, to do a good job to meet the standard intestinal preparation, so that your intestinal examination is a success, to avoid repeated examinations due to poor intestinal preparation. 1, bowel preparation before the dietary requirements 1-2 days before the examination to abstain from eating red or multi-seeded food, such as watermelon, tomatoes, kiwi, etc., so as not to affect the colonoscopy. The day before the examination lunch and dinner to eat less slag semi-liquid food such as thin rice, noodles, can not eat vegetables, fruits and other dregs of food and dairy products. And fast in the morning of the examination day, 4-6 hours before the endoscopy, take 2-3 L of polyethylene glycol isotonic solution, and finish it within 2 hours. If the afternoon examination still need to fast at noon, no diabetes friends can drink sugar water to prevent hypoglycemia. 2, preferred polyethylene glycol as bowel preparation drug Our guidelines recommend that patients be given polyethylene glycol bowel preparation is recommended to drink 2-3 L of water, and some patients who cannot drink a lot of water in a short period of time are recommended to have diet control 1 day before colonoscopy. The most ideal intestinal cleanser is polyethylene glycol preparation, which is a volumetric laxative that cleanses the intestine by emptying a large amount of digestive juices and does not affect intestinal absorption and secretion, therefore it does not lead to water and electrolyte balance disorders, and the common adverse effects are bloating and nausea. 3.How should laxatives be taken? The standard of intestinal cleansing is “colorless and dilute watery stool, no solid stool”. Let’s take “polyethylene glycol electrolyte dispersion” as an example to introduce the method of intestinal preparation. Dosing time: Start 4-6 hours before the examination for patients without constipation. How to take it: Pour all the polyethylene glycol electrolyte bulk into a large container, add warm boiled water to 2000-3000 mL and dissolve it fully, take 250 mL approximately every 10 min, take a quarter of it within half an hour and finish it within 2 hours. After taking the laxative for about half an hour then there will be “diarrhea”, usually around 7-10 times, until no solid fecal residue is visible, see the figure below. Precautions before colonoscopy (1) If you are chronically constipated, please explain to your doctor. You can take a small amount of lactulose or a small dose of magnesium sulfate solution 3 days before the examination. (2) If you routinely take antihypertensive medication, you can take it 1 hour before taking laxatives. Diabetic patients do not need to take their hypoglycemic medication because they are not eating. (3) Non-diabetic patients can drink some white sugar water if they show hypoglycemia (white sugar water has no color and will not affect the colonoscopy). (4) If you are menstruating, please explain to your physician to stagger your menstruation before having colonoscopy. (5) If you need treatment such as electrosurgery under colonoscopy and you are taking anticoagulants such as aspirin, clopidogrel, warfarin, etc. at the same time, be sure to explain to your physician. (6) After the examination, do not eat immediately, wait until the gas in the colon is expelled and the abdominal distension disappears, and then eat an easily digestible liquid food.