Internal medicine
Assistant Editor-In-Chief: Varun Shetty, M.B.B.S 

# Overview
Internal medicine is the branch and specialty of medicine concerning the diagnosis and nonsurgical treatment of diseases in adults, especially of internal organs.  Doctors of internal medicine, also called "internists",  are required to have included in their medical schooling and postgraduate training at least three years dedicated to learning how to prevent, diagnose, and treat diseases that affect adults. Internists are sometimes referred to as the "doctor's doctor," because they are often called upon to act as consultants to other physicians to help solve puzzling diagnostic problems. While the name "internal medicine" may lead one to believe that internists only treat "internal" problems, this is not the case. Doctors of internal medicine treat the whole person, not just internal organs. According to the American Medical Association, specialists of internal medicine earn between $175,000 to $350,000 per year.

# Definition of an Internist
Internists hold either an allopathic (MD,MBBS,MBChB,etc) or osteopathic (DO) degree.  They are not to be confused with "Medical Interns," who are physicians in their first year of residency training. Although Internists may act as primary care physicians, they are not "family physicians," "family practitioners," or "general practitioners" (whose training in certain countries includes the medical care of children, and may include surgery, obstetrics and pediatrics). General Internists practice medicine from a primary care perspective but they can treat and manage many ailments and are usually the most adept at treating a broad range of diseases affecting adults.
Internal Medicine sub-specialists may also practice general internal medicine, but can focus their practice on their particular subspecialty like cardiology or pulmonology after completing a fellowship. (Additional training of 2-3 years)
In the USA, adult primary care is usually provided by either family practice or general internal medicine physicians. The primary care of adolescents is provided by family practice, internists and pediatricians.  The primary care of children and infants is provided by Family Practice or Pediatricians. Thus, there is overlap.

## Caring for the whole patient
Internists are trained to solve puzzling diagnostic problems and handle severe chronic illnesses and situations where several different illnesses may strike at the same time. They also bring to patients an understanding of preventative medicine, men's and women's health, substance abuse, mental health, as well as effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs. Most older adults in the United States see an internist as their primary physician.

# Subspecialties of internal medicine
Internists can choose to focus their practice on general internal medicine, or may take additional training to "subspecialize" in one of 13 areas of internal medicine, generally organized by organ system. Cardiologists, for example, are doctors of internal medicine who subspecialize in diseases of the heart. The training an internist receives to subspecialize in a particular medical area is both broad and deep. Subspecialty training (often called a "fellowship") usually requires an additional one to three years beyond the standard three year general internal medicine residency. (Residencies come after a student has graduated from medical school.)
In the United States, there are two organizations responsible for certification of subspecialists within the field, the American Board of Internal Medicine, and the American Osteopathic Board of Internal Medicine.
The following are the subspecialties recognized by the American Board of Internal Medicine.
- Cardiology, dealing with disorders of the heart and blood vessels
- Endocrinology, dealing with disorders of the endocrine system and its specific secretions called hormones
- Gastroenterology, concerned with the field of digestive diseases
- Hematology, concerned with blood, the blood-forming organs and its disorders
- Infectious disease, concerned with disease caused by a biological agent such as by a virus, bacterium or parasite
- Medical oncology, dealing with the study and treatment of cancer
- Nephrology,dealing with the study of the function and diseases of the kidney
- Pulmonology, dealing with diseases of the lungs and the respiratory tract
- Rheumatology, devoted to the diagnosis and therapy of rheumatic diseases.
The ABIM also recognizes additional qualifications in the following areas
- Adolescent medicine
- Clinical cardiac electrophysiology
- Critical care medicine
- Geriatric medicine
- Interventional cardiology
- Sports medicine
- Transplant hepatology
Internists may also specialize in allergy and immunology. The American Board of Allergy, Asthma, and Immunology is a conjoint board between internal medicine and pediatrics.
The American College of Osteopathic Internists recognizes the following subspecialties.
- Allergy/Immunology
- Cardiology
- Critical care medicine
- Endocrinology
- Gastroenterology
- Geriatric medicine
- Hematology/Oncology
- Infectious diseases
- Nuclear medicine
- Nephrology
- Pulmonology
- Rheumatology

# Principles of diagnosis
The main tools of the doctors are the medical history and the physical examination, but this holds particularly true for internal medicine. Subtle descriptions of disease (e.g. cyclic shallow and deep breathing, as in Cheyne-Stokes's respiration, or persistently deep breathing as in Kussmaul's) or physical signs (e.g. clubbing in many internal diseases) are important tools in guiding the diagnostic process. In the medical history, the "Review of Systems" serves to pick up symptoms of disease that a patient might not normally have mentioned, and the physical examination typically follows a structured fashion.
At this stage, a doctor is generally able to generate a differential diagnosis, or a list of possible diagnoses that can explain the constellation of signs and symptoms. Occam's razor dictates that, when possible, all symptoms should be presumed to be manifestations of the same disease process, but often multiple problems are identified.
In order to "narrow down" the differential diagnosis, blood tests and medical imaging are used. They can also serve screening purposes, e.g. to identify anemia in patients with unrelated complaints. Commonly performed screening tests, especially in older patients, are an X-ray of the chest, a full blood count, basic electrolytes, renal function and blood urea nitrogen.
At this stage, the physician will often have already arrived at a diagnosis, or maximally a list of a few items. Specific tests for the presumed disease are often required, such as a biopsy for cancer, microbiological culture etc.

# Treatment
Medicine is mainly focused on the art of diagnosis and treatment with medication, but many subspecialties administer surgical treatment:
- Cardiology: angioplasty, cardioversion, cardiac ablation, intra-aortic balloon pump
- Gastroenterology: endoscopy and ERCP
Pulmonology:  Bronchoscopy
- Nephrology: dialysis
- Critical care medicine: mechanical ventilation

# Impact
Small primary care clinics that include at least one internist have better rates of prescribing statin according to the Healthy Hearts in the Heartland (H3) study.