Many patients come to the clinic with complaints of hematemesis, which can be clinically manifested as blood in the stool, blood dripping after stool, blood in the wipe after stool, black stool, etc. Except for black stool which mainly comes from the upper gastrointestinal tract, most blood in stool comes from the lower gastrointestinal tract, among which colorectal and anal lesions are the most common. There are many causes of blood in stool, the main causes are hemorrhoids, anal fissure, colorectal cancer, enteritis, ischemic bowel disease, intestinal vascular malformation, intestinal diverticulum, etc. If you have blood in your stool, you should not simply think that you have “hemorrhoids”, but go to a regular hospital and improve your colonoscopy and other related tests. Especially for older patients, the possibility of colorectal cancer is greater, so it is more important to take it seriously and delay treatment. In view of the gradually increasing incidence of malignant tumors and the trend of younger age, foreign countries have made colonoscopy a routine medical examination for people over 40 years old. We suggest that all patients over 35 years old with blood in stool should preferably be examined by colonoscopy to avoid misdiagnosis and missed diagnosis.