Gastroenterology (Digestive Disorders) Gastroenterology is a medical subspecialty concentrating on the digestive organs, including the stomach, bowels, liver, and gallbladder. The Gastroenterologist treats conditions such as abdominal pain, ulcers, diarrhea, cancer, and jaundice. Gastroenterologists perform complex diagnostic and therapeutic procedures using lighted scopes to see internal organs. James L. Stammer, M.D.