I shake my head when a patient with abdominal pain gets told they have “gastroenteritis.” Gastroenteritis means infection of the stomach (“gastro-“) or intestine (“entero-“), or both, or can’t tell which. If it’s in the stomach, there’s lots of nausea, usually vomiting. In the intestine, there’s significant diarrhea.
Those are the main symptoms, pain is the least important. If pain is the main symptom, it’s something else. If pain begins before the nausea or vomiting, it’s definitely something else. See Gastroenteritis and Staphylococcal Food Poisoning.