Gastroenterology is the study of the normal function and diseases of the oesophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts, and liver, according to the American College of Gastroenterology.
A gastroenterologist must have a thorough understanding of the normal physiology of all of the organs mentioned above, as well as motility through the intestines and gastrointestinal tract, in order to maintain healthy digestive process, absorption of nutrients, waste disposal, and metabolic functions.