Gastroenterology is the branch of medicine where the digestive system and its disorders are studied. Diseases affecting the gastrointestinal tract - the esophagus, stomach, small intestine, large intestine, pancreas, liver, gallbladder and biliary system are the focus of this speciality. Doctors specialising in the diagnosis and treatment of disorders of the gastrointestinal tract are called gastroenterologists. Hepatology or hepatobiliary medicine encompasses study of the liver, pancreas and biliary tree and is traditionally considered a subspeciality.