Gastroenterology - the subspecialty of Internal Medicine that specializes in the diagnosis, treatment, and prevention of diseases of the digestive tract including the esophagus, stomach, small and large intestines, liver and pancreas. Frequently, a gastroenterologist is consulted in cases of abdominal pain or discomfort in which the diagnosis is unclear or where specialized medical care is needed. The gastroenterologist performs an examination of the upper or lower intestinal tract with a fiberoptic endoscope.