When a patient with recurrent blood in stool was diagnosed with advanced rectal cancer, he said sadly, “If I had paid attention to blood in stool, I wouldn’t be like this”. In fact, there are many clinical lessons like this, and many people think that blood in the stool is just hemorrhoids, and the most direct consequence of tolerating or ignoring blood in the stool is that many diseases lose the best time for treatment. So what diseases can cause bleeding in the stool? Blood in stool is a signal of no less than dozens of anal and digestive tract diseases, and we can make self-judgment based on the way, amount, color and accompanying symptoms of blood in stool, in order to make timely and reasonable treatment of them. 1, upper gastrointestinal bleeding, stool is tarry or black, the bleeding site mostly lies in the upper gastrointestinal tract, that is, the stomach and duodenum bleeding is most likely. If the blood is red in color, it is mostly bleeding from lower GI tract diseases. However, if the upper gastrointestinal bleeding is large, the blood can also be red in color due to the short residence time of the blood in the digestive tract, which needs to be noted. 2, hemorrhoids is the most common cause of blood in the stool, this blood in the process of defecation or after the stool, the blood is bright red, blood and feces do not mix, in the form of drops and down, there are also jets out, the amount of bleeding can be large or small, can stop since, some also show a certain periodicity. Some patients have a small lump protruding outward from the anus when they struggle to defecate, but there is no anal pain. 3, anal fissure caused by blood in the stool is also more common in the clinic, blood is bright red, dripping out or hand paper wipe blood, different from hemorrhoids is often after defecation with severe pain in the anus. 4, rectal polyps, children with blood in the stool are mostly caused by this disease. The blood in the stool caused by polyps is bright red, painless, blood and stool do not mix, some patients with grooves on the surface of the stool, polyps grow to a certain length can come out of the anus with the stool. 5.Intestinal tumor, among the intestinal tumors, rectal cancer is most similar to hemorrhoid bleeding due to its lower location. Blood in the stool is bright red and attached to the surface of the stool in the form of drops, but most of it is mixed with mucus and dark blood clots in the blood or in the stool, and is accompanied by bad odor, and is persistent, accompanied by anorectal cramping and general wasting in the advanced stage, and the number of stools increases, and constipation alternates with diarrhea. Anorectal examination is the most convenient and economic means to detect anorectal tumor. 6, ulcerative colitis, dysentery and other diseases can also cause blood in the stool, and most of the blood in the stool caused by such inflammatory diseases of the large intestine is mixed with mucus or pus and blood, and accompanied by lower abdominal pain, fever, frequent stools and shortness of breath and other symptoms, which are common in adults. 7, in addition, some rare diseases, such as intestinal typhoid, intestinal tuberculosis, intussusception, etc., will also have the symptoms of blood in the stool. Systemic diseases such as leukemia, aplastic anemia, primary thrombocytopenic purpura, hemophilia, disorders of coagulation mechanisms, collagen disease, uremia, and certain rare infectious diseases such as plague and typhus can cause blood in the stool. However, in these diseases, blood in the stool is only a part of systemic bleeding, and blood in the stool is accompanied by bleeding from other parts of the body; therefore, it is not difficult to identify. It is still difficult to make accurate self-judgment based on the characteristics and symptoms of blood in the stool. It is best to go to the anorectal department for anal examination, especially anal finger examination combined with colonoscopy, which can make the diagnosis more accurate and enable early treatment.