A lot of blood in the stool is usually anal fissure, hemorrhoids or colitis caused by the following: First, anal fissure, anal fissure is the anal canal skin rupture and the formation of ulcers, mostly due to abnormal stool, inflammation stimulation or anatomical abnormalities caused by blood in the stool or blood on the paper as the main symptom, the blood is mostly bright red, accompanied by symptoms of pain. Second, hemorrhoids, divided into internal hemorrhoids and external hemorrhoids, the main symptom is blood in the stool, bleeding, usually not accompanied by pain, inflammation and thrombosis will occur when swelling and pain. Third, colitis, refers to the chronic non-specific inflammation that occurs in the sigmoid colon and rectum, the main symptom is diarrhea, accompanied by pus and blood and mucus, the blood is darker in color, attached to the surface of the stool, due to frequent diarrhea, the perianal area may have inflammatory reaction, resulting in anal fissure, anal fistula and other diseases.