Internal medicine is the branch of medicine that deals with diseases and disorders of all internal organs (lungs, kidneys, nervous system, and gastrointestinal tract)as well as diseases affecting the cardiovascular system, such as heart disease or high cholesterol. Internal medicine doctors are trained to deal with patients who are suffering from a disease that affects one or more of these areas of the body. They may also be in charge of the health care provider for an entire group of staff or hospital.