What is Gastroenteritis? Gastroenteritis refers to inflammation of the gastrointestinal tract, meaning the stomach and the intestines. It can be caused by infection with bacteria, viruses, parasites, medications, or even new foods. The condition often causes abdominal pain, diarrhea, vomiting, and/or other clinical signs. What are the signs of gastroenteritis? Most dogs with gastroenteritis will have