There are many kinds of diseases that can cause blood in the stool, the most common disease is hemorrhoids, hemorrhoids is the highest incidence of anorectal diseases, and blood in the stool is the most important symptom of hemorrhoids. Hemorrhoids blood in stool is characterized by bright red color, amount of more or less, without obvious pain. Another disease that is more common is anal fissure. Blood in the stool caused by anal fissure is characterized by bright red color, accompanied by severe anal tearing pain, and usually accompanied by the symptoms of constipation. In addition, rectal polyps can also cause blood in the stool, usually accompanied by abdominal pain and diarrhea. Ulcerative colitis can also cause blood in the stool, usually accompanied by mucus, pus and blood in the stool, as well as abdominal pain. In addition, in patients older than 40 years of age, the possibility of colorectal malignancy cannot be ruled out, which can also cause blood in the stool, usually dark in color. However, if the location is very low, the color of the blood in the stool may also be fresh, accompanied by anal discomfort, as well as recent changes in bowel habits. Therefore, if you have frequent blood in stool, you should go to the anorectal department of a regular hospital for examination and treatment, and it is recommended to have an electronic colonoscopy to make a clear diagnosis.