Diarrhea and black stools are commonly associated with gastric perforation, ruptured fundic varices, gastric cancer, intestinal perforation and other diseases. Black stools are related to many factors, and black stools are mainly due to diet, drugs and other factors when they are normal in nature. Once the color of the stool is black and the stool is dilute, you should be alert to the presence of gastrointestinal bleeding and need to confirm the diagnosis with fecal occult blood examination, as follows: 1. If there is an ulcer surface on the mucosa in the stomach and the ulcer surface is gradually aggravated, it will cause a gastric perforation attack. Gastric perforation will not only cause severe pain, but also lead to bleeding in the stomach, and some people’s blood will be discharged out of the body through the digestive system, and the feces will not only be black in color, but also thin. 2. Gastric varices are common in patients with advanced cirrhosis, and blood will enter the digestive system when the veins rupture, which will also cause diarrhea and black stools. 3. The symptoms are not obvious in the early stage, but in the late stage, it will not only affect the function of the stomach, but also lead to erosion and bleeding of the surrounding tissues, so diarrhea and black stools will also appear. 4. When intestinal perforation occurs, blood will enter the digestive system directly because of bleeding in the intestine, and will be discharged together with the stool, so the discharged stool is also black.