A gastroenterologist is a healthcare professional who has been educated and trained to treat patients who are experiencing health problems or have diseases that affect the gastrointestinal tract and liver. They also diagnose and treat diseases that affect the esophagus, stomach, small intestine, colon, rectum, pancreas, gallbladder, bile ducts, and liver.

An internist or Internal Medicine doctor is someone who specializes in diagnosing and treating illnesses, diseases, and health problems. Most internists are also primary care doctors and treat patients on a regular basis. They can diagnose and treat common illnesses or more serious problems. Most people see an internist regularly. Those with chronic illnesses may do so on a monthly or even weekly basis. Internists are the most common types of doctors.

A nephrologist is a medical professional who specializes in diagnosing and treating diseases and disorders that affect the kidneys. Nephrologists are often referred to as kidney specialists. Some nephrologists also do research that helps them learn more about kidney diseases, so they can produce better treatments for their patients.

A neurologist is a medical professional who specializes in the study and treatment of disorders that affect the brain and nervous system. The nervous system controls and regulates activity and movement in the body. If the nervous system is not functioning properly, the body cannot function. It is the job of a neurologist to find and correct any problems in the nervous system.