Blood in the stool is a symptom we often encounter in the clinic, but many people do not care about it, thinking they have “hemorrhoids”; some people, especially female patients, are reluctant to go to the hospital because of shyness; and so on. These patients often go to the pharmacy to buy some drugs for topical application, and the symptoms recur until they can’t handle it themselves when they go to the hospital. Many diseases are not diagnosed and treated early, resulting in irreversible consequences. Blood in the stool refers to blood mixed in the stool, or blood before and after the stool, or even the discharge of whole blood stool. Generally speaking, blood in stool is a manifestation of bleeding in the lower gastrointestinal tract, and the lesion is mainly located in the anal canal, rectum or colon, and sometimes in the small intestine. Blood in the stool can be caused by intestinal diseases or can originate from a variety of systemic diseases. The color of blood in the stool depends on the height of the bleeding site, the amount of bleeding and the length of time the blood stays in the intestine. In the lower part of the anus and rectum, the blood is often fresh or attached to the surface of the formed stool; in the upper part of the colon, the blood is often mixed evenly with the stool and has a saucy red color; in bleeding above the small intestine, if the blood stays in the intestine for a long time, it may pass tarry stool, and if the bleeding is large and fast, the higher bleeding may also pass dark red or bright red stool. Blood in the stool can be pure blood, but also with mucus coexistence. A disease that can cause blood in the stool 1, lower gastrointestinal tract lesions: anorectal diseases: anal canal diseases: hemorrhoids, anal fissures, anal fistula; rectal diseases: rectal inflammation (infectious, non-infectious), vascular lesions, rectal tumors (benign, malignant tumors and adjacent tumors infiltrate the rectum); rectal injury: hard fecal masses, foreign bodies and other damage to the rectal mucosa caused. Colon diseases: including inflammation (infectious and non-infectious), colonic diverticulitis and diverticular ulcers, colonic polyps, colonic tumors (benign and malignant), ischemic enteropathy, etc. Small intestine diseases: intestinal tuberculosis, intestinal typhoid, acute hemorrhagic necrotizing enteritis, Meckel’s diverticulitis and diverticular ulcer, malignant tumor and benign tumor. 2, lower gastrointestinal vascular lesions: ischemic enteropathy: mesenteric artery embolism or thrombosis, mesenteric vein thrombosis, intussusception, intestinal torsion, etc. Vascular wall lesions: allergic purpura, vitamin C and vitamin PP deficiency, hereditary capillary dilation, aneurysm breaking into the intestine, etc. 3, systemic diseases: acute infectious diseases: epidemic hemorrhagic fever, leptospirosis, etc. Blood disorders: thrombocytopenia or abnormal platelet function including primary thrombocytopenic purpura, leukemia, aplastic anemia, etc. Coagulation disorders: such as hemophilia, vitamin K deficiency. Uremia: late stage often leads to bleeding caused by intestinal mucosal erosion and ulceration. Rheumatic immune diseases: systemic lupus erythematosus, dermatitis and polyarteritis nodosa, etc. Tips: 1. When consulting the doctor, you should take the initiative to clarify the time of onset, the cause of onset, the blood in the stool, including the number of times, color, amount of blood in the stool, relationship with feces, accompanying symptoms and general status; 2. It is best to bring stool samples for laboratory tests. If imaging tests such as blood, urine, stool and colonoscopy, ultrasound, etc. have been done outside the hospital, it is better to bring the reports of the tests done in the past. This can provide clues to the doctor’s diagnosis. 3. Previous treatment and medication can be a good aid to the doctor’s diagnosis and treatment plan, so please bring your previous medical records and medication.