Colonoscopy generally refers to colonoscopy, and the scope of observation includes the mucosa of the rectum, colon, cecum, and the end of the ileum. Colonoscopy can detect the following diseases: 1. benign occupying lesions, such as polyps, lipomas, cysts, etc. These benign diseases do not have any symptoms and are usually found during physical examinations. If polyps are found they can be treated endoscopically, and small polyps can be removed on the spot. In case of larger polyps hospitalization is required and gastroscopic polypectomy is done again. Benign lesions such as lipomas and cysts can be followed up regularly and do not require special treatment; 2. Various malignant tumors such as colon cancer, lymphoma, neuroendocrine tumors, etc. Colon cancer and lymphoma often have corresponding clinical manifestations, and neuroendocrine tumors are usually asymptomatic and are also found during physical examinations; 3. Mucosal lesions, such as ulcerative colitis, ischemic enteritis, and colonic melanosis, etc.