Blood in stool is most commonly associated with anal diseases, such as internal hemorrhoids, anal fissure and other associated bleeding, as well as intestinal lesions such as colorectal cancer, colorectal polyps, colorectal inflammation and other associated bleeding. If the color of blood in the stool is bright red and clean, dripping blood when not defecating or blood on the surface of stool, it is mostly considered to be caused by anal diseases. If the blood in the stool is dark red in color and dirty, mixed with the stool, it is mostly considered to be colorectal lesions, such as colorectal cancer or larger colorectal polyps. If the blood in the stool has mucus and there is abdominal pain before defecation, it is mostly considered to be colorectal inflammatory diseases. In short, no matter which disease causes blood in the stool, it is recommended to the regular hospital anorectal department consultation, further anoscopy and colonoscopy to be clear, so as not to delay the condition.