Blood in the stool refers to the elimination of blood from the anus. The clinical manifestations are fresh blood in the stool, dark red blood in the stool, or tarry stool. It is clinically classified into overt and occult blood depending on the amount of bleeding. Many gastrointestinal diseases and systemic diseases can cause blood in the stool, but it is most common in the following anorectal diseases: a. Rectal injury Due to trauma or dry hard fecal masses, foreign bodies in the intestinal cavity abrasion rectal mucosa, anal canal mucosal skin, or due to rough inspection injury to the anal canal and bleeding, its color is bright red, mostly constipation or history of trauma, mild can be self-healing. Internal hemorrhoids Because of the increase in intra-abdominal pressure during defecation, the blood pressure in the internal hemorrhoid plexus rises, plus the direct friction of the fecal mass, resulting in the rupture of the internal hemorrhoid mucosa and bleeding, initially blood in the feces or blood on the hand paper, mostly accompanied by constipation, in the soft stool can be no blood in the stool symptoms, and then appear after the stool dripping blood. Later, as the hemorrhoid nucleus increases, bleeding can occur at any time when the hemorrhoid nucleus is prolapsed, and the patient can have spontaneous bleeding and serious blood in the stool, which can cause anemia for a long time, mostly in stage I and II internal hemorrhoids. Anal fissure is characterized by bleeding due to constipation and hard feces rubbing against the mucous membrane and skin of the anal canal, which is characterized by blood in the stool, the bleeding is small and irregular, intermittent, bright red, mostly on the surface of dry and hard stool or stained on the hand paper, accompanied by pain during defecation, persistent and severe pain after defecation, constipation and other typical symptoms, the clinical diagnosis is not difficult. 4.Anal rectal cancer Blood in stool is mostly fresh blood or dark red blood, which is not mixed with stool. It can be easily confused with dysentery. Rectal finger examination or sigmoidoscopy can confirm the diagnosis. V. Rectal polyps polyps are broken and bleeding by the friction of feces during defecation, manifested as intermittent or persistent painless blood in the stool, bright red, not much, not mixed with feces. It may also appear as persistent positive fecal occult blood, with right-sided colorectal polyps causing blood in the stool most commonly, or even causing anemia. If the polyp is large, it may be accompanied by abdominal discomfort, abdominal pain and diarrhea or polyp prolapse, etc. Sigmoidoscopy can confirm the diagnosis. Painless blood in the stool in children is often caused by polyps, mostly young polyps with misshapen nature, and the diagnosis can be confirmed by anal fingering. Six, ulcerative colitis with mucus blood stool as the main symptom, stool containing blood, pus, mucus, accompanied by abdominal pain, diarrhea and systemic symptoms, fiber colonoscopy can confirm the diagnosis, causing blood in the stool many diseases, do not think that bleeding stool is hemorrhoids, and buy drugs to self-serve, not to go to the doctor; also do not see blood in the stool is very nervous, suspected of having cancer. The right attitude should be to seek medical attention in time to find out the cause of the bleeding and to carry out purposeful treatment.