Hematemesis refers to acute upper gastrointestinal bleeding caused by upper gastrointestinal tract and systemic diseases, where blood is vomited through the mouth. There are many causes of blood vomiting, including the following: 1, esophageal diseases, including rupture of fundic varices, esophageal rupture, rupture of esophageal cancer, etc.; 2, gastric and duodenal diseases, including gastroduodenal bulb ulcer, gastric cancer, etc.; 3, liver and gallbladder lesions, commonly caused by rupture of fundic varices and bleeding due to cirrhosis; 4, bile duct cancer and potbelly cancer causing bleeding in large quantities into the duodenum; 5, pancreatic diseases, including acute pancreatic cysts and abscesses rupture into the duodenum; 6, gastrointestinal bleeding caused by diseases of adjacent organs of the gastrointestinal tract; 7, systemic diseases, such as hematological diseases, thrombocytopenic purpura, etc.; 8, less common fulminant hepatitis, sepsis, connective tissue diseases.