Gastroenterology is a medical specialty that involves the diagnosis and treatment of disorders of the digestive system.These disorders may affect the esophagus (food tube), stomach, small intestine, large intestine (colon), rectum, liver, gallbladder and pancreas.A Gastroenterologist is a physician who is trained in internal medicine and then spends several additional years of training in Gastroenterology. Most Gastroenterologists are board certified in Internal Medicine. Then after several years of practice and additional requirements, a physician can become board certified in Gastroenterology.