When black stool and blood in stool appear, first of all, gastrointestinal bleeding and hemorrhoids are considered, but the clinical condition of more and more patients is often not just ulcers and bleeding, but often combined with other inflammatory diseases or other diseases, especially cancer is common, such as gastric cancer, colon cancer, rectal cancer, so unexplained black blood in stool is further examined. In recent years, the incidence of gastrointestinal malignant tumors is not only high in middle-aged and old people, but also its youthfulness is becoming more and more obvious. These cancers often have no symptoms and signs in the early stage, but are only detected in the middle and late stage when inflammation and ulcers cause bleeding and lead to black stool, but many patients miss the time for treatment because they do not pay attention to them. Gastrointestinal endoscopy (gastroscopy) is the first choice for the diagnosis and examination of this kind of digestive tumor. Once diagnosed, surgery should be performed as early as possible to improve the prognosis and avoid delaying the disease. In foreign countries, gastroenteroscopy is a routine procedure, but in China, due to different national and economic conditions, this test is often not available. Why do black stools appear? Black stool and blood in the stool are two forms of gastrointestinal bleeding in humans. Generally speaking, if the GI bleeding exceeds 60 ml per day, but is not too much or too concentrated, black stool can appear, which is medically known as tarry stool. Otherwise, if there is more or more concentrated blood that can be seen with the naked eye, it is called hematochezia. In general, black stool or blood in the stool often comes out of nowhere without clinical symptoms, so the patient is often at a loss as to what to do. However, if one can carefully observe the color, quality, and quantity of the black stool or the bleeding area and amount of blood in the stool, one can analyze the changes in the condition. First, the amount of bleeding can be estimated based on the color and quality of the stool. Gastrointestinal bleeding of more than 60 ml per day can be characterized as black stool. If the stool is constantly black and dry, it means that there is a small amount of continuous bleeding; if the stool turns from black to dark red or bright red, and the stool is soft and thin, even with blood clots in between, it means that there is active bleeding in the digestive tract, and the amount of bleeding is also more. Second, according to the color and quality of the stool, determine the bleeding site of what disease. Medically, the digestive tract is divided into three sections: upper, middle and lower, and the bleeding in the three sections manifests itself differently during the stool. If you have blood in your stool first and then in your stool and the blood is bright red, it means that the source of blood is closer to the anus and the bleeding site is usually in the rectum or anus, which is common in rectal cancer, hemorrhoids, anal fissure, rectal polyps, etc.; if you have blood in your stool first and then in your stool, the color is as black as road tar, which means that the source of blood is farther away and stays in the intestine for a longer time, and the bleeding site is mostly in the stomach and duodenum, colon or small intestine, such as stomach or duodenal ulcer, gastric cancer, gastric polyp, etc. Third, according to the color and quality of the stool to determine whether there is continued bleeding. If the black stool gradually turns yellow, it means that the bleeding has stopped; if the black stool persists, it means that the bleeding has increased; if the black stool turns yellow after treatment and then black stool appears, it means that there is re-bleeding or the disease has recurred. Fourthly, the amount of bleeding can also be judged according to the clinical manifestations such as mental and facial expressions. Generally speaking, if the bleeding is slow and the bleeding volume does not exceed 300 ml, the clinical symptoms are not obvious or only slightly dizziness and weakness, etc.; the clinical appearance of dizziness, palpitation, pale face, rapid pulse and thirst, etc. indicates that the bleeding volume has exceeded 400 ml per day; if the bleeding continues to exceed 1000 ml, it will be life-threatening.