The cause of blood in the stool: Blood coming out with the bowel movement or mixed with stool is called blood in the stool. The bleeding drops of blood that can be seen with the naked eye during defecation are generally considered. Blood in stool or pus and blood in stool is called dominant bleeding; bleeding that cannot be seen with the naked eye and requires laboratory tests to detect is called occult bleeding. Clinically, it is often classified according to the site of onset: upper gastrointestinal bleeding lower gastrointestinal bleeding systemic disease bleeding. 1, upper gastrointestinal bleeding esophagus, inflammation of the stomach and duodenum, injury, vascular lesions, tumors. 2, lower gastrointestinal bleeding: (1) anal canal disease: hemorrhoids anal fissure anal fistula. (2) rectal inflammation rectal tumor rectal injury. (3) Colon and small intestine diseases: infection and parasites. Inflammation . Tumors. (4) Vascular lesions: ischemic colitis. Allergic purpura. Vitamin C and vitamin P deficiency. Hereditary capillary dilation, etc. 3, systemic diseases: (1) coagulation disorders (2) platelet factors (3) uremic syndrome (4) connective tissue diseases (5) acute infectious diseases