Gastroenterology (MeSH heading) 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.