Colonoscopy, also called colonoscopy, is a diagnostic modality used to examine the large intestine and the inside of the colon for lesions. Contrary to gastroscopy, colonoscopy is performed by using a thin, direct tube of only about 1 cm through the anus to insert the colonoscope through the lumen to the ileocecal region, thus entering the rectum and extending to the large intestine. The colon tissue is observed for lesions mainly from the mucosal side, and is by far the best way to diagnose whether or not you have an intestinal disease. Colonoscopy is the easiest, safest and most effective method to detect intestinal tumors and precancerous lesions. However, after all, endoscopy is an invasive examination method with certain discomfort and complications, therefore, there are many people who are afraid of this examination, resulting in some colorectal lesions or even tumors not being diagnosed early and delaying the best time for treatment. Traditional colonoscopy can be painful; electronic colonoscopy is not painful. Many patients with anorectal diseases are afraid of pain once they hear that they need to do colonoscopy. With the progress of medical level, the current electronic colonoscopy has become popular in China, painless electronic colonoscopy, is no pain. First, the preparation work before doing colonoscopy 1, three days before the examination diet should be light, the day before do not eat fiber-rich fruits and vegetables, the day of the examination fasting. 2, many methods of intestinal cleansing, each hospital uses different drugs, should be prepared for the intestine according to medical advice. For those who take oral medication to cleanse the intestines, drink more water after taking medication, and finally discharge stools in clear water or light yellow, without fecal residue, for the best intestinal cleansing effect. Second, to do anoscopy precautions 1, after taking the drug, if the discharge contains feces or fecal water-like liquid, should promptly tell the colonoscopy medical staff for further intestinal processing. 2, in order to facilitate access to the mirror or to see the mucosal pattern of the intestinal cavity, doctors sometimes need to inject a small amount of air into the intestinal cavity to expand or expose the intestinal cavity, the patient often feel bloated and have the feeling of relieving stool. 3, colonoscopy in the passage, it is best to take a deep breath, do not overstress, otherwise intestinal spasm is likely to occur, increasing the difficulty and risk of doctors into the mirror, prolonging the operation time. 4, the average examination takes about 15 minutes, sometimes due to individual differences, or abnormalities in the large intestine, the examination time may be a little longer. 3, the examination should pay attention to the following matters 1, 3 days before the examination, stop taking iron drugs, start eating a semi-liquid or low residue diet, such as fish, eggs, milk, soy products, porridge, noodles, bread, bananas, winter melon, potatoes, etc. 2.Take a light laxative the night before the examination, and drink more water at the same time. 3, the day of the examination into the dregs-free liquid diet or fasting, 2 hours before the examination clean bowel cleansing, half an hour before the examination, quiet rest. 4, during the examination, the patient first take the left side lying position, abdomen relaxed, and bend knees. Change the position during the examination as requested by the doctor. 5.If there is pain during the examination, tell the doctor immediately to facilitate safe insertion of the mirror. 6.Rest 1-2 days after the examination, if there is severe abdominal pain, abdominal distension, blood in the stool, etc., you should immediately go to the hospital for consultation. 7.If biopsy is performed, do not do strenuous activities for 3 days after the operation. 8.Severe heart disease, cardiopulmonary insufficiency, severe hypertension, acute diarrhea, severe ulcerative colitis, colonic Crohn’s disease, peritonitis, pregnancy, mental illness, and multiple abdominal surgeries with obvious adhesions are prohibited to do this examination.