There are especially many causes of stool bleeding, which should be combined with medical history, physical examination and, if necessary, anoscopy or colonoscopy to clarify the causes. First, if there is a history of trauma or foreign body invasion into the anus, such as a foreign body inserted into the anus, it can lead to rectal mucosa or anal canal skin fracture, which can lead to bleeding, and anoscopy can clearly find the fracture. Second, if hemorrhoids are not treated in a timely manner, they can lead to bleeding in the case of increased abdominal pressure or constipation. Third, such as anal fissures, dry stools can easily damage the anal canal and the skin leads to fissures, which leads to blood on the surface of the stool. Fourth, there may be rectal polyps and rectal adenomas, long-term stimulation in the feces, the rectal submucosa blood vessels rupture, thus wiping the stool with blood on the surface of the stool, so there are many reasons for sudden bleeding in the stool.