Preparation of the intestinal tract before colonoscopy: Since the presence of feces in the intestinal cavity can seriously affect the diagnosis and treatment of colonoscopy, it is important to keep the intestinal cavity clean when undergoing colonoscopy, so it is very important to prepare the intestinal tract beforehand, and the success or failure of colonoscopy is closely related to good or bad intestinal preparation. Before undergoing colonoscopy, the doctor will usually ask about the condition, perform a physical examination, read the imaging data already done such as barium enema x-rays (if available), etc., and then inform the patient of the purpose, significance and precautions of the colonoscopy and sign an informed consent form, and finally arrange the date and place of the consultation. Among the precautions, the doctor will especially emphasize the importance of cleansing the bowel. In the method of preparation before colonoscopy, the process of exploration such as simple dietary preparation, enema cleansing method, and oral laxative is experienced. Diet preparation and enema cleansing methods often interfere with access and observation due to fecal residue and are rarely used now. Oral laxatives are more effective in cleansing the bowel, but generally the diet should be adjusted before taking laxatives, i.e., 3 days before the date of the consultation. This is done by eating a semi-liquid diet with little residue, no vegetables, fruits or dried fruits, especially those with seeds or kernels, 3 days before the consultation. The first 1 day eat a dregs-free, low-fat, soft, liquid diet, such as rice soup, lotus root powder, etc., without drinking milk. Fasting is required for breakfast on the day of the morning consultation, and a small amount of liquid food can be eaten for breakfast on the day of the afternoon consultation. The laxatives available are: 1. Senna: Usage: 9 grams of water 1000 ml, 5 hours of tea before operation. The advantage is the low price, the disadvantage of mucous membrane irritation and abdominal pain, nausea, weakness, etc. 2, mannitol: Usage: 250 ml of 20% mannitol orally 2 hours before the consultation, then drink quickly into 500 ml of 5% sugar saline. Advantages are no irritation to the large intestine mucosa, drinking less water, the patient can easily accept. Disadvantage is that the decomposition of bacteria in the colon to produce flammable gas hydrogen and methane, in the presence of heat such as electrocoagulation treatment is easy to explode. 3, magnesium sulfate: usage: 4 hours before the consultation and treatment orally 50% magnesium sulfate 100 ml, and then within 1 hour orally warm boiled water 2000 ml. Advantages are low price, disadvantages are abdominal pain, vomiting, thirst, etc., severe cases will have a slowed heartbeat, blood pressure drop, intestinal bleeding and allergy to this drug is prohibited, serious cardiovascular disease, respiratory disease and severe renal insufficiency patients with caution. 4.Electrolyte solution: Usage: Electrolyte powder (trade names include Shu Tai Qing, Fu Qing Jing, He Shuang, etc.) is dissolved in water according to the instructions and consumed as prescribed 5 hours before the consultation, usually 3000 ml of the solution should be consumed within 2 hours. The advantage is that there is no inflammatory reaction in the intestinal mucosa, it is safe and not easy to dehydrate. The disadvantage is that the amount of water consumed is high and some patients cannot drink as much as required resulting in suboptimal intestinal cleansing. In addition, attention should be paid to sleep and rest during preparation. If there are symptoms of hypoglycemia such as dizziness, panic and cold sweat, sugar water or intravenous glucose should be consumed.