Blood in stool refers to the discharge of blood from the anus during defecation. The blood can be bright red, dark red, or tarry, and bleeding can occur in the form of blood dripping from the anus during or after defecation, blood spraying, blood on the surface of the stool, or blood-stained hand towels after defecation, etc. Sometimes blood is mixed with stool, pus, or mucus. However, it is common to have blood in the stool or blood dripping from the stool. The amount of blood can be large or small. The color of the blood in the stool depends on the height of the bleeding site in the digestive tract. The upper gastrointestinal tract such as the esophagus, stomach, duodenum, and the liver, biliary tract, and pancreas tend to have black or tarry black stools when bleeding occurs. The lower gastrointestinal tract, such as the small intestine, colon, rectum, and anal canal, tend to have bright red blood in the stools. However, there can be exceptions to both. Acute upper gastrointestinal hemorrhage with accelerated bowel movements may result in bright red blood stools without black stools. In the case of small intestine bleeding, if the blood stays in the intestine for a longer period of time. When the small intestine bleeds a lot and is discharged quickly, the stool is dark red or even bright red loose stool. When the colon and rectum bleeding, because the blood stays in the intestine for a short time. In the case of bleeding from the colon and rectum, the blood stays in the intestines for a shorter period of time. So what diseases can cause blood in the stool and what are the specific manifestations that require us to be alert? The most common cause of blood in the stool is hemorrhoids. There is a Chinese saying that “nine out of ten people have hemorrhoids”, and it is especially common for elderly men to suffer from hemorrhoids. The hemorrhoids are divided into internal, external and mixed hemorrhoids depending on the location of occurrence. The reason for hemorrhoids is that due to gravity and organ compression, venous blood is blocked from flowing back, forming a thrombus. Prolonged standing, sitting, squatting, constipation, excessive alcohol consumption and spicy food can cause the onset of the disease. Bleeding hemorrhoids are usually intermittent, mostly in the form of bright red blood dripping after a bowel movement or blood on hand paper, the blood does not mix with the stool and is often painless, often relieved by itself after improving diet or rest. Anal fissures can also have fresh blood in the stool, but they are often accompanied by a “rupture sensation” during defecation and periodic pain in the anus. Secondly, colon and rectal tumors, especially rectal cancer, are also a common cause of blood in the stool. It is manifested as dark red blood in the stool, or pus and mucus stool, blood is often mixed with stool, and there are also discomfort symptoms of defecation such as lower abdominal cramping, shortness of breath, change in bowel habits and stool characteristics, and general discomfort symptoms such as emaciation, malnutrition and weight loss. It is important to be alert to the fact that hemorrhoids and rectal cancer may coexist in the elderly, and people generally always treat blood in the stool as an attack of hemorrhoids. Due to this misunderstanding, many people tend to use some medication for hemorrhoids on their own once they have blood in their stool, thus delaying the discovery of the real condition, which is already confirmed to be mid to late stage, missing the best time for treatment. Anyone considering bleeding hemorrhoids should be further examined to rule out the possibility of rectal cancer in time, otherwise misdiagnosis or omission will easily occur. Rectal polyps and sigmoid polyps refer to lesions on the mucosal surface of the rectum or sigmoid colon that bulge toward the intestinal lumen. After the stool, there is fresh blood or dark red blood stained outside the stool, rectal polyps are occasionally accompanied by polyp prolapse. This disease is prone to malignancy, after a clear diagnosis should be taken early endoscopic high-frequency electric knife or other procedures to remove polyps to prevent cancer. There is also blood in the stool of colitis, Crohn’s disease and other inflammatory diseases of the colon, often mucus and blood stools, often with abdominal pain, diarrhea and other manifestations. In addition, food poisoning, bacterial dysentery, amoebic dysentery, etc. can cause blood in the stool, and small intestinal diseases and other uncommon causes can also lead to blood in the stool. How to prevent blood in the stool in daily life? The simplest and most effective way is to eat more fruits and vegetables to soften the stool, try to avoid prolonged standing, prolonged sitting, prolonged squatting, avoid excessive drinking and eating spicy food, drink more water, eat more dietary fiber, keep the stool open, and develop good habits of rest and bowel habits. Do not be overly nervous when you have blood in the stool, but go to the anorectal department of the hospital as soon as possible. Generally, the specialist can find out the cause of bleeding by asking medical history, rectal diagnosis, proctoscopy, colonoscopy and pathological examination, make a correct diagnosis, and provide professional advice to you to choose the appropriate prevention and control measures, not because of luck or paralysis of thought and give up medical treatment, allowing the development of the disease, resulting in irreversible consequences.