Blood in the stool may be caused by anal fissure, hemorrhoids and proctitis. 1. Anal fissure: Anal fissure is a small ulcer formed after cracking the skin layer of the anal canal below the dentate line, which is usually a mechanical injury caused by hard stools and too much force when defecating, and because the fissure triggers the bleeding of the fissure, the anal fissure patients usually have a knife-like or burning pain in the anus. If the patient does not want to defecate because of the pain, constipation may occur with time, and the stool is hard and coarse, so the anal fissure patient will have the phenomenon of hard and coarse stool with blood when defecating. 2. Hemorrhoids: hemorrhoids are usually caused by prolonged sitting and standing, pregnancy, constipation and other behaviors that cause obstruction of venous return in the anal canal, blood vessels dilate, triggering the accumulation of venous masses caused by hemorrhoids, hemorrhoids volume will increase with time, hemorrhoids volume increases may lead to narrowing of the intestinal lumen, defecation pain, combined with constipation will make hemorrhoids rupture resulting in the phenomenon of stools rough and hard with blood. 3. proctitis: enteritis is caused by a variety of factors of inflammation of the rectal lining, usually due to ulcerative colitis, gonorrhea, syphilis, rectal injuries, inflammatory factors will repeatedly stimulate the rectum, thus triggering rectal mucosal edema, congestion, combined with constipation will appear in the stool coarse and hard with blood symptoms. In addition to the above situation, the blood in the stool is hard and thick does not exclude other causes, and it is recommended that the patient go to the hospital for treatment.