Acute gastroenteritis is rapid onset of inflammation of the stomach and small intestine. Common causes are eating spoiled food, garbage, dead fish or animals, bones, plastic, wood, chemicals, drugs or toxic plants. Vomited material may sometimes reveal what the animal ate, but often the offending material is never isolated. Other causes of acute gastroenteritis include viral or bacterial infections, parasites, foreign material (bones, garbage, plant material) and food allergy. The cause of gastroenteritis is often difficult to determine. A careful history of what your pet may have had access to is often helpful. Most cases will respond to symptomatic support. If improvement is not seen with symptomatic treatment, or if worsening occurs, diagnostic studies such as radiographs, blood work, fecal exam and endoscopy may be needed. Hospitalization and intravenous fluids may be necessary in severe cases.