Gastroenterology is the branch of medicine focused on the digestive system and its disorders. In the United States, gastroenterology is an internal medicine subspecialty certified by the American Board of Internal Medicine (ABIM) and the American Osteopathic Board of Internal Medicine (AOBIM).
Diseases affecting the gastrointestinal tract, which include the organs from mouth to anus, along the alimentary canal, are the focus of this specialty. Physicians practicing in this field are called gastroenterologists. They have usually completed eight years of pre-medical and medical education, a year-long internship (if this is not a part of the residency), three years of an internal medicine residency, and two to three years in the gastroenterology fellowship. Some gastroenterology trainees will complete a "fourth-year" (although this is often their 7th year of graduate medical education) in transplant hepatology, advanced endoscopy, inflammatory bowel disease (IBD), motility or other topics.
Hepatology, or hepatobiliary medicine, encompasses the study of the liver, pancreas, and biliary tree, and is traditionally considered a sub-specialty.