What is the need for colonoscopy? The consensus in the United States and the Asia-Pacific region for colorectal cancer screening is that people over the age of 50 should have a colonoscopy. In the United States, it is stipulated that all people over the age of 50 (the latest information shows that people over the age of 40 must have colonoscopy screening, otherwise they will not apply for health insurance) must have a proctoscopy once every three years, and the incidence of colitis, intestinal polyps, rectal cancer and other intestinal diseases is on the rise. Then what is the necessity of colonoscopy? Chinese bowel cancer disease is earlier than the West, so it is advocated that the first colonoscopy should be done after the age of 40. After the age of 50 in the United States, even if one feels healthy, the family doctor will recommend and arrange for a colonoscopy for the insured during the annual routine physical examination. Our domestic colonoscopy data show that the detection rate of colon polyps colonoscopy varies from 14.39% to 17.8%. General statistics show that the incidence of colorectal cancer is about 5 times higher than that of those with colon polyps without colon polyps. The autopsy incidence has been reported to be 11.7%-14.6%, among which adenomas and villous adenomatous polyps over 1 cm have about 40%-52.9%m chance of carcinogenesis. Therefore, adenoma and villous adenomatous polyps are called precancerous lesions of the colon. Since colon polyps are deep inside the human colon, smaller polyps usually have no obvious symptoms; larger polyps, especially left-sided colon polyps, may show symptoms such as diarrhea, abdominal pain, mucus and bloody stools if erosion, ulceration and bleeding occur.