There are many causes of bleeding in the stool, which are mostly seen in hemorrhoids, inflammatory bowel disease, intestinal tumors and so on. 1. Hemorrhoids: hemorrhoids are varicose veins, if the stool is dry or abdominal pressure increases, it is easy to cause the hemorrhoid nucleus to swell, causing the veins to rupture and cause bleeding. 2. Inflammatory bowel disease: for example, patients with ulcerative colitis will easily cause pus and blood in the stool. 3. Intestinal tumors: such as rectal adenoma or malignant tumors of rectal colon, if the course of the disease is long, it will invade the mucosa and submucosal blood vessels, resulting in bleeding in the stool. Therefore, the causes of blood in stool are very complicated, which need to be combined with the patient’s medical history, physical examination, colonoscopy or anoscopy if necessary, to clarify the location of bleeding and the specific causes, so as to systematically treat under the guidance of the doctor.