Gastroenteritis caused by different reasons has different symptoms, such as abdominal pain, diarrhea, abdominal distension, early fullness after meals, loss of appetite, belching, acid reflux, nausea and so on. And severe diarrhea and vomiting can cause dehydration and electrolyte disorder. Gastroenteritis caused by acute stress or drugs, and hematemesis and melena. For infectious gastroenteritis, the onset is often urgent, and it may also be accompanied by symptoms such as fatigue and watery stool. People with food poisoning are often seriously ill a few hours after eating, and in severe cases, mucus-like purulent bloody stools may appear. There are also patients with non-infectious gastroenteritis who have no symptoms or obvious symptoms, or have nonspecific dyspepsia, such as abdominal pain, abdominal distension and postprandial fullness. In addition, anorexia, belching and acid regurgitation may occur, and in severe cases, hematemesis and melena may also occur.