An inflammation of the stomach and/or intestinal lining. It is one of the most common causes of nausea, vomiting and diarrhea. Gastroenteritis has numerous causes: including infectious organisms (viruses, bacteria, etc.), food poisoning, and stress. This disorder can be very serious in the very young and very old causing life threatening dehydration. Internationally this is one of the leading causes of death of patients of all ages.