A gastroenterologist is a specialist in diagnosis and treatment of conditions involving the digestive/gastrointestinal (GI) tract. These doctors are experts on how food moves through the digestive system and is chemically broken down, with nutrients being absorbed and waste excreted. You might see this kind of doctor if you are experiencing any number of stomach issues, some of which might be severe diarrhea, irritable bowel syndrome, hemorrhoids, ulcers, acid reflux, Crohn's disease and more.

A hepatologist is a physician who specializes in the diagnosis and treatment of diseases of the liver, gall bladder, pancreas and biliary tree - the path through which bile that is secreted by the liver travels to the duodenum. These organs are responsible for many essential bodily functions, such as production of hormones and enzymes, filtering the blood, detoxifying chemicals, metabolizing drugs, and digesting and processing food.Common disorders that are treated by hepatologists are cirrhosis of the liver, gallstones, pancreatitis and hepatitis.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.