Gastroenterology is the branch of medicine dealing with the study of disorders affecting the stomach, intestines, and related organs of the gastrointestinal tract. These disorders may affect the esophagus (food tube), stomach, small intestine, large intestine (colon), rectum, liver, gallbladder and pancreas. In gastroenterology, doctors diagnose and treat diseases that are as varied as the digestive tract itself, from heartburn to colorectal cancer. Gastroenterology, a subspecialty of internal medicine, is so broad that many doctors specialize in diseases of particular parts of the digestive system, such as the liver and gallbladder.