A general internist provides medical care for adolescents and adults. The general internist provides comprehensive care of common and complex illnesses in the office, as well as in the hospital. If they deem it necessary, they may refer to a specialist in an outpatient setting. While in the hospital, they may ask a specialist to come for additional consultation. Generally, they are the one in charge of orchestrating, in complicated cases, the different specialists who may be asked for consultations. Internists May Sub-Specialize In: Cardiovascular Medicine: Cardiologists sub-specialize in diseases of the heart, lungs, and blood vessels and manage conditions such as heart attacks. They often perform complicated diagnostic procedures such as cardiac catheterization. Critical Care Medicine: This internist has sub-specialized in managing life-threatening acute disorders in intensive care units. Endocrinology: The endocrinologist concentrates on disorders of the internal (endocrine) glands such as the thyroid and adrenal glands. They evaluate and treat diseases such as diabetes, hypothyroidism, and glandular disorders. Gastroenterology: This subspecialty treats the digestive organs which includes the stomach, bowels, liver, and gallbladder. The gastroenterologist treats conditions such as abdominal pain, ulcers, diarrhea, cancer, and jaundice, and consults with surgeons when abdominal operations indicated. Gastroenterologist examine the hollow organs through lighted endoscopes and, through these flexible tubes, can biopsy lining tissues and remove small polyps. Geriatric Medicine: Geriatric Medicine is not regarded as a subspecialty, but rather as an added competence in trained internists. The elderly have special needs since they often have an altered presentation of illness and special drug interactions. Hematology: Hematologists sub-specialize in diseases of the blood, spleen, and lymph glands. They treat conditions such as anemia, clotting disorders, sickle cell disease, hemophilia leukemia and lymphoma. They may perform special types of transfusions and biopsy the bone marrow for analysis as is required for diagnosing and treatment. Infectious Disease: These sub-specialists deal with infectious diseases of all types and in all organs. Conditions requiring selective use of antibiotics call for this special skill. Patients with fevers which have not been explained are often diagnosed and treated by these sub-specialists, as well as rare and exotic infections with bacteria, viral, and fungi. They are especially suited to help in the treatment of patients who may present multiple and unique infections. Medical Oncology: The medical oncologist specializes in the diagnosis and treatment on all types of cancer and other benign and malignant tumors. These sub-specialists also decide on and administer chemotherapy for malignancy, as well as consult with surgeons and radiotherapists on treatment for cancer. Nephrology: The nephrologist is concerned with disorders of the kidney which may produce hypertension and fluid and mineral imbalance. They are the ones chiefly involved in running dialysis units. Dialysis is the mechanical removal of body wastes by a machine when the kidneys do not function. Pulmonary Disease: Pulmonary Disease is the subspecialty concerned with diseases of the lungs and other chest tissues. The pulmonologist diagnoses and treats diseases such as pneumonia, cancer of the lung, asthma, bronchitis and emphysema. Pulmonologists test lung functions in many ways, including visually with the bronchoscope and other pulmonary functions studies. Many pulmonary disease experts supervise critical care units. Rheumatology: Rheumatologists are concerned with diseases of joints, muscles, bones, and tendons. The rheumatologist diagnoses and treats arthritis, various types of back pain, muscle strains, and common athletic injuries. They are especially trained to treat and recognize diseases of the connective tissue and arteries in many body systems called "collagen" diseases, for example, scleroderma and lupus.