The nonsurgical specialties that involve direct patient care include internal medicine, medical genetics, pediatrics, allergy and immunology, dermatology, preventive medicine, and psychiatry and neurology.
Practitioners of internal medicine, or internists, are concerned with the diagnosis and treatment of adults with diseases of the internal organs. Those called general internists are primary-care physicians, in that they have a direct relationship with patients on a long-term basis and refer them to other specialists only for specific problems. Many internists specialize in a specific area of the body. This has led to the formation of nine subspecialties. Cardiology is the care of patients with diseases of the heart and blood vessels. Endocrinology and metabolism is the care of patients who have problems related to glands of the body. Gastroenterology is the study of diseases of the gastrointestinal tract; it also deals with diseases of the liver and pancreas. Hematology treats patients with diseases of the blood cells, bone marrow, and lymph nodes; hematologists also operate blood banks and manage patients with blood-clotting disorders. Infectious disease specialists are consulted chiefly in the treatment of severe or exotic infections, the selection and use of antibiotics, and the management of complications resulting from their use. Specialists in nephrology are experts in the diagnosis and treatment of kidney diseases, also managing blood-dialysis centers for patients who lack functioning kidneys. Oncology involves the treatment of cancer patients with chemotherapeutic agents; oncologists frequently act in the capacity of general internists for such patients. Pulmonary disease is concerned with disease of the lung and air passages. Finally, rheumatology specialists treat patients with joint diseases and joint-related systemic diseases such as rheumatoid arthritis and lupus erythematosus.
Medical genetics deals with diagnosing and treating patients with genetic diseases. Because tests exist for a number of genetic diseases, specialists can set up necessary preventive treatment where possible, as well as offering genetic counseling, prenatal diagnosis, and coordinating screening programs for some genetic diseases.
Pediatrics is constituted much like internal medicine, but it deals instead with infants and children. The new field of adolescent medicine, however, has extended these traditional age limits. Recognized pediatric subspecialties include pediatric cardiology, hematology/oncology, endocrinology, and nephrology. These subspecialties differ from their adult counterparts, because infants and children have distinctive diseases and disease patterns. One subspecialty unique to pediatrics is neonatal-perinatal medicine, dedicated to the management of premature infants and ill newborns. Specialists in this field also aid in caring for a child at risk before birth.
Allergy and immunology, besides dealing with hypersensitivity disorders such as asthma and food allergies, also treats immune-related problems such as patients with organ transplants and patients incapable of manufacturing components of the immune system. A practitioner in this field has already completed training as an internist or a pediatrician.
Dermatology is the study of diseases of the skin. Since the majority of human diseases have at least some effect on the skin, this field of medicine intersects with many other specialties. The dermatologist must understand the systemic diseases likely to be responsible for a skin rash, just as the internist or pediatrician examines the skin as a first clue to underlying disease. Occupational dermatology is the study of skin manifestations resulting from some factor in work areas.
Preventive medicine studies means of improving the level of health in a community. Most work in the area of preventive medicine and public health is done under the aegis of a government, university, or institute, and many such specialists are public-health officers. Those interested in such a career customarily attend a School of Public Health and receive a master's degree, the MPH. Training encompasses a thorough grounding in statistics, epidemiology, microbiology, and immunology. Holders of an MPH are often not physicians, but physicians form a necessary element in public-health organizations. Two subspecialties exist: occupational medicine, devoted to detecting and measuring adverse effects of the workplace; and aerospace medicine.
Psychiatry and neurology is divided into two obvious subspecialties. Psychiatry is concerned with those brain functions expressed as behavior, mood, and intelligence, whereas neurology is concerned with organic diseases of the central nervous system, including the brain. In general, psychiatrists treat patients with nonorganic diseases of the brain, whereas neurologists treat those with organic diseases. Organic diseases are those in which the immediate cause can be observed directly or under a microscope or can be identified chemically, while nonorganic diseases are those in which no anatomical or chemical basis is identifiable. Psychiatrists also spend much of their professional time treating emotional responses to chronic disease.