A gastroenterologist is a medical doctor who specializes in diagnosing and treating disorders of the gastrointestinal (GI) tract, which includes the esophagus, stomach, small intestine, large intestine (colon), liver, gallbladder, pancreas, and rectum Gastroenterologists are responsible for diagnosing a wide range of digestive system disorders and diseases. This involves taking detailed medical histories from patients, performing physical examinations, and ordering and interpreting diagnostic tests such as endoscopies, colonoscopies, imaging studies (like X-rays, CT scans, and MRIs), blood tests, and stool tests.