Many patients are not sure what is going on with blood in the stool, in clinical medicine, the so-called blood in the stool is the discharge of blood from the anus, blood mixed with stool and black stool, what diseases are the main causes of blood in the stool? 1, hemorrhoids, especially internal hemorrhoids, is the common cause of bleeding after stool, clinical manifestations of painless jet bleeding, blood color bright red, may also be dripping blood after the stool, will be aggravated after drinking alcohol or eating spicy and irritating food. 2, anal fissures are also a common cause of blood in the stool, but anal fissures usually have severe pain before and after defecation, and blood in the stool is bright red in color. 3, intestinal polyps can also cause blood in the stool, the blood is bright red in color, no pain, often accompanied by abdominal pain and diarrhea and other manifestations, may be accompanied by malnutrition, anemia, etc. 4, rectal and anal tumors are also the cause of blood in the stool, blood color is usually dark red or sauce-colored blood, no pain in the early stage, easy to cause anemia, often accompanied by the feeling of urgency or unclean, foul-smelling stool. In short, when there is blood in the stool do not be too nervous, first determine the color of the bleeding, and then determine whether there is pain, the nature of bleeding, etc., and then promptly go to the hospital, formal examination, in order to make a diagnosis.