Gastroenterology is the study of the digestive system, including the esophagus, stomach, small intestine, colon, rectum, pancreas, gallbladder, bile ducts, and liver. A gastroenterologist, also known as a GI doctor, specializes in the diagnosis, treatment, and prevention of digestive diseases. 
You might see a gastroenterologist if you have unexplained or frequent digestive issues, such as: abdominal discomfort, changes to your bowel habits, gas, and vomiting. 

Some conditions that a gastroenterologist might treat include:
Irritable bowel syndrome (IBS)
Inflammatory bowel disease (IBD)
Celiac disease
Small intestinal bacterial overgrowth (SIBO)
Food allergies and intolerances
Stomach ulcers
Diverticulitis
Appendicitis 

Gastroenterologists are trained in internal medicine and receive additional training in problems of the digestive system. They treat GI conditions medically (such as with medicines) and perform nonsurgical procedures, such as colonoscopies.