Colonoscopy is usually used in clinical practice to detect unexplained gastrointestinal bleeding, chronic diarrhea, intestinal obstruction, intestinal tumors, etc., and plays an important auxiliary role in the diagnosis of these diseases. If patients have the following symptoms for unknown reasons, they may need to follow medical advice to do colonoscopy to assist in diagnosis. 1, gastrointestinal bleeding: when there is a change in stool color, such as dark red, bright red or black, it is suspected that there is gastrointestinal bleeding or occupying lesions, and they need to do colonoscopy to clarify the internal condition of the gastrointestinal tract; 2, abdominal pain: patients who have unexplained abdominal pain need to do colonoscopy to further confirm the diagnosis 3, abdominal masses: patients with unexplained abdominal masses also need to do colonoscopy to see if there are lesions in the large intestine and the end of the ileum; 4, change in bowel habits: patients with no cause of constipation or diarrhea symptoms, too dry stools or watery stools, alert to intestinal lesions, through colonoscopy can help clarify the situation; 5, chronic diarrhea: patients with no cause of long-term diarrhea, and 5. chronic diarrhea: if patients have diarrhea for a long time without any cause and no other symptoms, they need to undergo colonoscopy to clarify whether it is caused by organic lesions inside the intestine; 6. severe nausea and vomiting: when patients have nausea, vomiting and inability to defecate, and sudden intestinal obstruction is suspected to occur without any cause, the clinic will mostly determine whether it is caused by intestinal lesions through colonoscopy.