Routine colonoscopy can usually be performed on an outpatient basis and usually does not require general anesthesia and does not require hospitalization. If some patients are overly nervous an anesthetic can be used to avoid discomfort while performing the colonoscopy, an operation that is usually completed within half an hour. During this procedure, the doctor may biopsy the polyps found in the lining of the colon (mucosa) and should also take a small sample of the lining of the colon (mucosa) from the suspected area for laboratory testing, which is clearly superior to other tests. Some scholars believe that the accuracy of colonoscopy is higher and advocate to use colonoscopy directly as a screening tool, but because it is more invasive, most people believe that only high-risk groups can consider this method, such as people over 50 years old in areas with a high incidence of colorectal cancer should be examined once a year for fecal occult blood, and those who are positive should undergo full colonoscopy. In fact, colorectal cancer is not a sudden lesion of intestinal mucosa, but develops through the sequence of normal mucosa – adenoma – carcinoma, which is a slow process, usually taking 5-10 years, and existing studies have found that more than 80% of colorectal cancer is transformed from colorectal adenoma. So who needs regular colonoscopy? The high-risk groups of colorectal cancer should receive regular colonoscopy and other examinations. These include: 1) health checkups for people aged over 50 in areas with high incidence of colorectal cancer; 2) people with intestinal symptoms such as recurrent black stools or positive fecal occult blood and no lesions detected on upper gastrointestinal examination, and people with abnormal bowel movements such as chronic diarrhea or long-term progressive constipation; 3) family members with a history of colorectal cancer or adenoma; 4) follow-up checkups after medication for inflammatory bowel disease; 5) people who need regular colonoscopy after surgery for colorectal cancer or polyps. Follow-up review after surgery or endoscopic treatment for colorectal cancer or polyps; 6. Those with a history of pelvic radiotherapy and gallbladder removal.