Internal medicine physicians, also known as internists, are specially trained to diagnose and treat nonsurgical conditions and diseases of internal organs and systems that affect adults. Internists, who promote and help their patients maintain good overall health, focus on the entire patient instead of a particular organ system. For many patients, their internist acts as their primary care physician. Internists treat conditions in the nervous, digestive, endocrine and circulatory systems, conditions that may affect the heart, lungs, kidneys, eyes, ears and skin. In addition, internists treat high blood pressure, hypertension, heart disease and common illnesses such as the flu.