4-year-old children with stomach pain, fever and diarrhea may be caused by acute gastroenteritis, mesenteric lymphadenitis and other causes. 1. Acute gastroenteritis: when 4-year-old children suffer from acute gastroenteritis, it will easily lead to the invasion of viruses and bacteria, causing inflammation of the gastrointestinal tract, in the stimulation of inflammation, there may be a tummy ache, fever, diarrhea and so on. 2. Mesenteric lymphadenitis: If a 4-year-old child suffers from mesenteric lymphadenitis, it may be caused by bacterial, viral, parasitic and other pathogens infection, mainly manifested as stomach pain, fever, diarrhea, vomiting and other symptoms. When a 4-year-old child has stomach pain, fever and diarrhea, parents should take the child to the pediatrics department of the hospital in a timely manner, after a clear diagnosis, follow the doctor’s instructions, so as not to delay the condition.