Gastroenterology
Gastroenterology is a subspecialty of internal medicine concerned with organ systems including the esophagus, stomach, small intestine and colon (anatomy), liver, pancreas, gall bladder and biliary ducts. Physicians who practice the specialty are called gastroenterologists, and may further subspecialize.
While gastroenterologists are not considered surgeons or radiologists, they often do specialized invasive procedures with endoscopic or intravascular instrumentation. Often, they work in teams with relevant surgical specialties.
Graduate medical education
Training for the field usually involves a 2-3 year fellowship following completion of an internal medicine residency. Some training programs are called "gastroenterology and hepatology", or sometimes "gastrenterology, hepatology and nutrition". While, for example, a given tertiary subspecialist may primarily do specific procedure, the field is less inclined to designate formal tertiary subspecialties. This contrasts, for example, with cardiology, where one might be an electrophysiologist or invasive cardiologist, and even go through quaternary training for techniques of interventional cardiology such as percutaneous trransluminal coronary angioplasty.
Organs, subspecialties and techniques
Esophagus
Stomach
The discovery of Helicobacter pylori as the major cause of stomach ulcers has transformed the treatment of that disease. Still, diagnosis may require upper endoscopy for direct viewing and nonsurgical biopsy, and cooperation with radiology for various dynamic imaging studies.
Liver
Subspecialists in liver disease are hepatologists. They are experts in the various forms of hepatitis, cirrhosis, and primary and metastatic liver cancer. For viral hepatitis, they work with infectious disease specialists, and with medical and radiation, and surgical oncologists for cancer.
Pancreas
Gastroenterologists are most concerned with the interactions of the pancreas with other parts of the digestive system, cooperating with endocrinologists to deal with the systemic actions of pancreatic hormones. An endocrinologist may be trained in nonsurgical invasive procedures such as retrograde cholangiopancreatography (ERCP), while a general surgeon would be required for open operation such as pancreaticoduodenectomy (Whipple procedure).
Biliary subsystem
They may treat stones in the biliary tract with drugs or with lithotripsy.