(1) Acute simple gastritis: Acute simple gastritis can be caused by chemical substances, physical factors, microbial infections, or bacterial toxins. The main lesions of the gastric mucosa are congestion and edema, increased mucus secretion, with white or yellow exudates covering the surface, accompanied by petechial bleeding and mild erosion. The onset of this disease is often sudden, with symptoms mainly including discomfort, pain in the upper abdomen, loss of appetite, nausea, and vomiting. Patients whose conditions are caused by infection are often associated with acute enteritis, showing diarrhea and periumbilical pain. Severe cases may present with fever, dehydration, acidosis, or even shock.