Diarrhea and stomach pain are related to acute gastroenteritis, appendicitis, and gastrointestinal dysfunction, as follows: 1. The acute gastroenteritis attack will cause irritation to the intestinal wall because of the presence of inflammation in the intestinal system. The intestinal system will spasm and contract under the stimulation of inflammation, and the peristaltic speed will increase, and abdominal pain and diarrhea will occur. Acute gastroenteritis also causes damage to the function of the stomach, resulting in the stomach not being able to discharge food normally and causing a feeling of distension and pain. 2. Appendicitis is mainly manifested by pain in the right lower abdomen, which not only affects the function of the intestines during an attack, but also causes spasm and contraction of the intestinal wall due to the stimulation of inflammatory substances and diarrhea. The pain of appendicitis is radioactive and even affects the stomach, causing pain in the stomach, accompanied by nausea and vomiting. 3. When the stomach and intestines become dysfunctional, the stomach wall becomes spasmodic and contracted, so there is pain in the stomach.