There are many unexplained abdominal pains, a large part of which are caused by colonic diverticulitis, colon polyps, colon tumors, ulcerative colitis, etc. The examination of colonoscopy is to further clarify the diagnosis and standardize the treatment. Colonoscopy is the first and foremost condition to further clarify the diagnosis and standardize the treatment. However, most patients are afraid of colonoscopy. This article introduces the purpose of colonoscopy, which is to improve the compliance of colonoscopy, early detection of neoplastic diseases and early treatment. What is colonoscopy? Colonoscopy is a bendable 140cm-long fiber optic tube with a light source and a microelectronic camera at the end, which is slowly passed through the anus into the large intestine to examine lesions, tumors or ulcers in the large intestine, and if necessary, to obtain tissue for examination or to remove polyps from the large intestine. What conditions need to be examined? 1.Unexplained lower gastrointestinal bleeding; 2.Unexplained chronic diarrhea; 3.Unexplained low intestinal obstruction; 4.Suspected tumor of the large intestine or the end of the ileum; 5.Large intestinal polyps, tumor bleeding and other lesions that require colonoscopy; 6.Post colon surgery and colonoscopy treatment requires regular review of colonoscopy; 7.Colon cancer screening; 8.Patients with colorectal cancer or adenoma in the family, who need to be examined; 9. Health checkups for people over 40 years old who have never had a colonoscopy before. Is colonoscopy painful? At present, most hospital colonoscopies are painless, and the whole procedure takes about 20~30 minutes.