Blood in the stool, no blood on the paper may have a bleeding site in the colon, which may be caused by intestinal necrosis, rupture and bleeding of colonic polyps or tumors. 1. Intestinal necrosis: when colorectal necrosis and bleeding occurs, the blood vessels rupture and the blood is discharged through the intestinal tract, causing blood in the stool, but there is no blood on the paper. In this case, we have to improve the relevant examination immediately to find out the necrosis and the bleeding site, and if necessary, remove the necrotic intestinal tubes. 2. Rupture of colonic polyps or tumors: If colorectal polyps or tumors suddenly rupture the surface mucosa under the action of various factors, it will also cause blood in stool. At this time, we should improve the examination and follow the doctor’s instruction to treat with surgery, radiotherapy and chemotherapy (such as 5-FU, furacil, etc.) after clear diagnosis. There are many causes of blood in the stool, so please consult a doctor as soon as possible, complete the examination, and follow the doctor’s instructions after a clear diagnosis.