A physician who specializes in Internal Medicine is a personal physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults, and the elderly. Also called Internists, these physicians are trained in the diagnosis and treatment of cancer, infections, as well as diseases affecting the heart, blood, kidneys, joints, digestive, respiratory, and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health, and effective treatment of common problems of the eyes, ears, skin, nervous system, and reproductive organs.