If your stomach is upset, or you're constipated, or for some reason you can't keep your food down, you may be referred to a gastroenterologist.
Gastroenterologists take care of problems related to our digestive systems. So if your primary care doctor refers you to a gastroenterologist for stomach upset, that makes sense.
If you have migraines, or a backache, or a tingling feeling in your hands or feet, you may be referred to a neurologist. A neurologist is trained to diagnose and care for problems with the head, neck, back, balance, reflexes and other problems including memory and cognitive abilities.
Both gastroenterologists and neurologists are specialists that focus on those specific diseases and body systems rather than more general medical problems like your primary care doctors does. The gastroenterologist or neurologist may pull out all the stops in trying to diagnose you. She will gather evidence in a variety of ways by observing you and your symptoms, running tests and studying your medical history. In the perfect world, she will figure out exactly what's wrong with your body, based on her specialized knowledge.
But sometimes it's not that easy. Sometimes a specialist may still have a problem determining your true diagnosis. Sometimes our symptoms are felt in one part of our bodies, or in one fashion, but they aren't really reflective of the right body system or an easily identifiable medical diagnosis.
For example: headaches can be caused not just by neurological problems, but by sinus problems, infections, high blood pressure, dental problems, eye diseases, arthritis – hundreds of causes. Those problems are treated by ophthalmologists, endocrinologists, rheumatologists, dentists and other specialists - not neurologists.
Stomach problems may have other causes than those related to your digestion, too. From liver problems to female problems to thyroid diseases, rather than getting a diagnosis from a gastroenterologist, you may need to see a gynecologist, urologist or an endocrinologist to get the right answers for you.