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Medicine is a branch of health science concerned with restoring and maintaining health. Broadly, it is the practical science of preventing and curing diseases. However, medicine often refers more specifically to matters dealt with by physicians and surgeons.

Medicine is both an area of knowledge (a science), and the application of that knowledge (by the medical profession and other health professionals such as nurses). The various specialized branches of the science of medicine correspond to equally specialized medical professions dealing with particular organs or diseases. The science of medicine is the knowledge of body systems and diseases, while the profession of medicine refers to the social structure of the group of people formally trained to apply that knowledge to treat disease.

There are traditional and schools of healing which are usually not considered to be part of (Western) medicine in a strict sense (see health science for an overview). The most highly developed systems of medicine outside of the Western or Hippocratic tradition are the Ayurvedic school (of India) and traditional Chinese medicine. The remainder of this article focuses on modern (Western) medicine.

History of medicine

See the main articles History of medicine and Timeline of medicine and medical technology

Medicine as it is practiced now is rooted in various traditions, but developed mainly in the late 18th and early 19th century in Germany (Rudolf Virchow) and France (Jean-Martin Charcot and others). The new, "scientific" medicine replaced more traditional views based on the "Four humours". The development of clinical medicine shifted to the United Kingdom and the USA during the early 1900s (Sir William Osler, Harvey Cushing).

Evidence-based medicine is the recent movement to link the practice and the science of medicine more closely through the use of the scientific method and modern information science.

Genomics is already having a large influence on medical practice, as most monogenic genetic disorders have now been linked to causative genes, and molecular biological techniques are influencing medical decision-making.

Practice of medicine

The medical encounter or patient-doctor relationship is an important part of what medicine is about (there are other relationships between health professionals and patients that are equally important, e.g. nurse - patient). A person with a health problem or concern sees a doctor for help. The practice of medicine combines both science and art. Science and technology are the evidence base for many clinical problems for the general population at large. The art of medicine is the application of this medical knowledge in combination with intuition and clinical judgment to determine the proper diagnoses and treatment plan for this unique patient.

The doctor needs to:

develop a relationship with the patient
gather data (medical history and physical examination combined with laboratory or imaging studies)
analyze and synthesize that data (assessment and/or differential diagnosis), and then
develop a treatment plan (more testing, therapy, watchful observation, referral and follow-up).

The medical encounter is documented in a medical record. One method that is used is called the problem-oriented medical record (POMR), which includes a problem list of diagnoses and a "SOAP" method of documentation for each visit:

S - Subjective, the medical history of the problem from the point-of-view of the patient.
O - Objective, the physical examination and any laboratory or imaging studies.
A - Assessment, is the medical decision-making process including the differential diagnoses and most probable diagnoses.
P - Plan, the way resolve the problem and monitor progress

Medical systems

Medicine is practiced within the medical system of a particular culture or government. Leaving aside tribal cultures, the most significant divide in developed countries is that between universal health care and the market based health care (such as practiced in the US).

Patient-doctor relationship

The doctor-patient relationship and interaction is the central process in the practice of medicine. There are many perspectives from which to understand and describe it.

An idealized physician's perspective, such as is taught in medical school, sees the core aspects of the process as the physician learning from the patient his symptoms, concerns and values; in response the physician examines the patient, interprets the symptoms, and formulates a diagnosis to explain the symptoms and their cause to the patient and to propose a treatment. In more detail, the patient presents a set of complaints or concerns about his health to the doctor, who then obtains further information about the patient's symptoms, previous state of health, living conditions, and so forth, and then formulates a diagnosis and enlists the patient's agreement to a treatment plan. Importantly, during this process the doctor educates the patient about the causes, progression, outcomes, and possible treatments of his ailments, as well as often providing advice for maintaining health. This teaching relationship is the basis of calling the physician doctor, which originally meant "teacher" in Latin. The patient-doctor relationship is additionally complicated by the patient's suffering (patient comes from the Latin patiens, "suffering") and limited ability to relieve it on his own. The doctor's expertise comes from his knowledge about, or experience with, other people who have suffered similar symptoms, and his presumed ability to relieve it with medicines or other therapies about which the patient may initially have little knowledge.

The doctor-patient relationship can be analyzed from the perspective of ethical concerns, in terms of how well the goals of non-maleficence, beneficence, autonomy, and justice are achieved. Many other values and ethical issues can be added to these. In different societies, periods, and cultures, different values may be assigned different priorities. For example, in the last 30 years medical care in the Western World has increasingly emphasized patient autonomy in decision making.

The relationship and process can also be analyzed in terms of social power relationships (e.g., by Michel Foucault), or economic transactions. Physicians have been accorded gradually higher status and respect over the last century, and they have been entrusted with control of access to prescription medicines as a public health measure. This represents a concentration of power and carries both advantages and disadvantages to particular kinds of patients with particular kinds of conditions. A further twist has occurred in the last 25 years as costs of medical care have risen, and a third party (an insurance company or government agency) now often insists upon a share of decision-making power for a variety of reasons, reducing freedom of choice of both doctors and patients in many ways.

The quality of the patient-doctor relationship is important to both parties. The better the relationship in terms of mutual respect, knowledge, trust, shared values and perspectives about disease and life, and time available, the better will be the amount and quality of information about the patient's disease transferred in both directions, enhancing accuracy of diagnosis and increasing the patient's knowledge about the disease.

Clinical skills

A complete medical evaluation includes a medical history, a physical examination, appropriate laboratory or imaging studies, analysis of data and medical decision making to obtain diagnoses, and treatment plan.

The components of the medical history are:

Chief complaint (CC) - the reason for the current medical visit.
History of present illness (HPI) - the chronological order of events of symptoms. A mnemonic PQRST is sometimes helpful in obtaining the history:
- Provocative-palliative factors - what makes a symptom worse or better.
- Quality - description of the symptom
- Region - which part of the body is affected
- Severity - what is the intensity of the symptom; using a scale of 0-10 (10 worst)
- Timing - what is the course of the symptom
Current activity - occupation, hobbies, what the patient actually does.
Medications - what drugs including OTCs, and home remedies. Drug allergies are important
Past medical history (PMH) - other medical diagnoses, past hospitalizations and operations, injuries, past infectious diseases and/or vaccinations
Review of systems (ROS) - an outline of additional symptoms to ask which may be missed on HPI, generally following the body's main organ systems (heart, lungs, digestive tract, urinary tract, etc.)
Social history (SH) - birthplace, residences, marital history, social and economic status, habits including diet, drugs, tobacco, alcohol
Family history (FH) - listing of diseases in the family that may impact the patient. A family tree is sometimes used.

The physical examination is the examination of the patient from head to toe looking for signs of disease. The doctor uses his senses of sight, hearing, touch, and sometimes smell (taste has been replaced by modern lab tests). Four chief methods are used: inspection, palpation, percussion, and auscultation; smelling may be useful (e.g. infection, uremia, diabetic ketoacidosis).

Vital signs include height, weight, body temperature, blood pressure, pulse, respiration rate, hemoglobin oxygen saturation
General appearance of the patient
Skin
Head, eye, ear, nose, and throat (HEENT)
Cardiovascular - heart and blood vessels
Respiratory - lungs
Abdomen and rectosigmoid
Genitalia
Spine and extremities - musculoskeletal
Neuropsychiatric

Laboratory and imaging studies results, if any.

Medical decision making (MDM) process involves the analysis and synthesis of all the above data to come with a list of possible diagnoses (the differential diagnoses) and what needs to be done to come up with a final diagnosis which would explain the patient's problem.

Treatment plan may include ordering additional labs and studies, starting therapy, referring to a specialist, or watchful observation. Follow-up may be needed.

This process is used by primary care providers and well as specialists. It may take only a few minutes if the problem is simple and straightforward. Or it may take weeks for a patient who has been hospitalized with multiple system problems involving several specialists.

On subsequent visits, the process may be repeated in an abbreviated manner to obtain any new history, symptoms, physical findings, and lab or imaging results or specialist consultations.

Settings where medical care is delivered

See also clinic, hospital, and hospice

Medicine is a diverse field and the provision of medical care is therefore provided in a variety of locations.

Primary care medical services are provided by physicians or other health professionals who has first contact with a patient seeking medical treatment or care. These occur in physician's office, clinics, nursing homes, schools, home visits and other places close to patients. About 90% of medical visits can be treated by the primary care provider. These include treatment of acute and chronic illnesses, preventive care and health education for all ages and both sex.

Secondary care medical services are provided by medical specialists in their offices or clinics or at local community hospitals for a patient referred by a primary care provider who first diagnosed or treated the patient. Referrals are made for those patients who required the expertise or procedures performed by specialists. These include both ambulatory care and inpatient services, emergency rooms, intensive care medicine, surgery services, physical therapy, labor and delivery, endoscopy units, diagnostic laboratory and medical imaging services, hospice centers, etc. Some primary care providers may also take care of hospitalized patients and deliver babies in a secondary care setting.

Tertiary care medical services are provided by specialist hospitals or regional centers equipped with diagnostic and treatment facilities not generally available at local hospitals. These include trauma centers, burn treatment centers, advanced neonatology unit services, organ transplants, high-risk pregnancy, radiation oncology, etc.

Modern medical care also depends on information - still delivered in many health care settings on paper records, but increasingly nowadays by electronic means.

Branches of medicine

The delivery of modern health care depends, not just on medical practitioners, but on an expanding group of highly trained professionals coming together as an interdisciplinary team. A full list is given on the health profession page. Some examples include: nurses, laboratory scientists, pharmacists, physiotherapists, speech therapists, occupational therapists, dietitians and bioengineers.

The scope and sciences underpinning human medicine overlap many other fields. Dentistry and psychology, while separate disciplines from medicine, are sometimes also considered medical fields. Physician assistants, nurse practitioners and midwives treat patients and prescribe medication in many legal jurisdictions. Veterinary medicine applies similar techniques to the care of animals.

Medical doctors have many specializations and subspecializations which are listed below.

Basic sciences

Anatomy is the study of the physical structure of organisms. In contrast to macroscopic or gross anatomy, cytology and histology are concerned with microscopic structures.
Biochemistry is the study of the chemistry taking place in living organisms, especially the structure and function of their chemical components.
Biostatistics is the application of statistics to biological fields in the broadest sense. A knowledge of biostatistics is essential in the planning, evaluation, and interpretation of medical research. It is also fundamental to epidemiology and evidence-based medicine.
Cytology is the microscopic study of individual cells.
Embryology is the study of the early development of organisms.
Epidemiology is the study of the demographics of disease processes, and includes, but is not limited to, the study of epidemics.
Genetics is the study of genes, and their role in biological inheritance.
Histology is the study of the structures of biological tissues by light microscopy, electron microscopy and histochemistry.
Immunology is the study of the immune system, which includes the innate and adaptive immune system in human, for example.
Microbiology is the study of microorganisms, including protozoa, bacteria, fungi, and viruses.
Neuroscience is a comprehensive term for those disciplines of science that are related to the study of the nervous system. A main focus of neuroscience is the biology and physiology of the human brain.
Nutrition is the study of the relationship of food and drink to health and disease, especially in determining an optimal diet. Medical nutrition therapy is done by dietitians and is prescribed for diabetes, cardiovascular diseases, weight and eating disorders, allergies, malnutrition and neoplastic diseases.
Pathology is the study of disease - the causes, course, progression and resolution thereof.
Pharmacology is the study of drugs and their actions.
Physiology is the study of the normal functioning of the body and the underlying regulatory mechanisms.
Toxicology is the study of hazardous effects of drugs and poisons.

Diagnostic specialties

Clinical laboratory sciences are the clinical diagnostic services which apply laboratory techniques to diagnosis and management of patients. In the United States these services are supervised by a Pathologist. The personnel that work in these medical laboratory departments are technically trained staff, each of whom usually hold a medical technology degree, who actually perform the tests, assays, and procedures needed for providing the specific services.
- Transfusion medicine is concerned with the transfusion of blood and blood component, including the maintenance of a "blood bank".
- Cellular pathology is concerned with diagnosis using samples from patients taken as tissues and cells using histology and cytology.
- Clinical chemistry is concerned with diagnosis by making biochemical analysis of blood, body fluids and tissues.
- Hematology is concerned with diagnosis by looking at changes in the cellular composition of the blood and bone marrow as well as the coagulation system in the blood.
- Clinical microbiology is concerned with the in vitro diagnosis of diseases caused by bacteria, viruses, fungi, and parasites.
- Clinical immunology is concerned with disorders of the immune system and related body defenses. It also deals with diagnosis of allergy.
Radiology is concerned with imaging of the human body, e.g. by x-rays, x-ray computed tomography, ultrasonography, and nuclear magnetic resonance tomography.
- Interventional radiology is concerned with using imaging of the human body, usually from CT, ultrasound, or fluoroscopy, to do biopsies, place certain tubes, and perform intravascular procedures.
- Nuclear Medicine uses radioactive substances for in vivo and in vitro diagnosis using either imaging of the location of radioactive substances placed into a patient, or using in vitro diagnostic tests utilizing radioactive substances.

Clinical disciplines

Anesthesiology (AE), Anaesthesia (BE), is the clinical discipline concerned with providing anesthesia. Pain medicine is often practiced by specialised anesthesiologists.
Dermatology is concerned with the skin and its diseases.
Emergency medicine is concerned with the diagnosis and treatment of acute or life-threatening conditions, including trauma, surgical, medical, pediatric, and psychiatric emergencies.
General practice or family medicine or primary care is, in many countries, the first port-of-call for patients with non-emergency medical problems. Family doctors are usually able to treat over 90% of all complaints without referring to specialists.
Geriatrics is concerned with medical care of the elderly.
Hospital medicine is the general medical care of hospitalized patients. Doctors whose primary professional focus is hospital medicine are called hospitalist.
Intensive care medicine is concerned with the therapy of patients with serious and life-threatening disease or injury. Intensive care medicine employs invasive diagnostic techniques and (temporary) replacement of organ functions by technical means.
Internal medicine is concerned with diseases of inner organs and systemic dieseases of adults, i.e. such that affect the body as a whole. There are several subdisciplines of internal medicine:
- Cardiology is concerned with the heart and cardiovascular system and their diseases.
- Gastroenterology is concerned with the organs of digestion.
- Endocrinology is concerned with the endocrine system, i.e. endocrine glands and hormones.
- Hematology (or haematology) is concerned with the blood and its diseases.
- Infectious diseases is concerned with the study, diagnosis and treatment of diseases caused by biological agents.
- Nephrology is concerned with diseases of the kidneys.
- Oncology is devoted to the study, diagnosis and treatment of cancer and other malignant diseases.
- Pulmonology (or chest medicine, respiratory medicine or lung medicine) is concerned with diseases of the lungs and the respiratory system.
- Rheumatology is devoted to the diagnosis and treatment of inflammatory diseases of the joints and other organ systems.
Neurology is concerned with the diagnosis and treatment of nervous system diseases.
Obstetrics and gynecology are concerned respectively with childbirth and the female reproductive and associated organs. Reproductive medicine and fertility medicine is generally practiced by gynecological specialists.
Palliative care is a relatively modern branch of clinical medicine that deals with pain and symptom relief and emotional support in patients with terminal disease (cancer, heart failure).
Pediatrics (or paediatrics) is devoted to the care of children, and adolescents. Like internal medicine, there are many pediatric supspecialities for specific age ranges, organ systems, disease classes and sites of care delivery. Most subspecialities of adult medicine have a pediatric equivalent such as pediatric cardiology, pediatric endocrinology, pediatric gastroenterology, pediatric hematology, and pediatric oncology.
Physical medicine and rehabilitation (or physiatry) is concerned with functional improvement after injury, illness, or congenital abnormality.
Preventive medicine
- Community health care or public health
- Occupational medicine
Psychiatry is a branch of medicine that studies and treats mental disorders. Related non-medical fields are psychotherapy and clinical psychology. There are several subdisciplines of Psychiatry:
- Child & adolescent psychiatry focuses on the care of children and adolescents with mental/emotional/learning problems (i.e., ADHD, Autism, family conflicts).
- Geriatric psychiatry focuses on the care of elderly people with mental illnesses (i.e., dementias, post stroke cognitive changes, depression).
- Addiction psychiatry focuses on substance abuse and its treatment.
- Forensic psychiatry focuses on the interface of psychiatry and the Law.
Radiation therapy is concerned with the therapeutic use of ionizing radiation and high energy elementary particle beams in patient treatment.
Radiology has both diagnostic and therapeutic branches. Diagnostic radiology utilizes X-rays, CT scans, ultrasound and MRI to diagnose disease. Interventional radiology uses these imaging techniques to guide treatments for certain diseases.
Surgical specialties - there are many medical disciplines that employ operative treatment. Some of these are highly specialized and are often not considered subdisciplines of surgery, although their naming might suggest so.
- General surgery is traditionally defined as the specialty of surgery of the skin, endocrine glands, and abdomen (and, sometimes, the mammary glands). In some countries, it is still deemed a pre-requisite training prior to progression to training in certain sub-specialties, but lately has evolved into its own sub-specialty.
- Cardiovascular surgery is the surgical specialty that is concerned with the heart and major blood vessels of the chest.
- Neurosurgery is concerned with the operative treatment of diseases of the nervous system.
- Maxillofacial surgery (technically a subspeciality of dentistry)
- Ophthalmology deals with the diseases of the eye and their treatment.
- Orthopedic surgery consists on surgery of the locomotor system.
- Otolaryngology (or otorhinolaryngology or ENT/ear-nose-throat) is concerned with treatment of ear, nose and throat disorders. The term head and neck surgery defines a closely related specialty which is concerned mainly with the surgical management of cancer of the same anatomical structures.
- Pediatric surgery treats a wide variety of thoracic and abdominal (and sometimes urologic) diseases of childhood.
- Plastic surgery includes aesthetic surgery (operations that are done for other than medical purposes) as well as reconstructive surgery (operations to restore function and/or appearance after traumatic or operative mutilation).
- Surgical oncology is concerned with curative and palliative surgical approaches to cancer treatment
- Urology focuses on the urinary tracts of males and females, and on the male reproductive system. It is often practiced together with andrology ("men's health").
- Vascular surgery is surgery of "peripheral" blood vessels, i.e. those outside of the chest (usually operated on by cardiovascular surgeons) and of the central nervous system (treated by neurosurgery).

Interdisciplinary fields

Interdisciplinary sub-specialties of medicine are:

Aerospace medicine deals with medical problems related to flying and space travel.
Bioethics is a field of study which concerns the relationship between biology, science, medicine and ethics, philosophy and theology.
Clinical pharmacology is concerned with how systems of therapeutics interact with patients.
Conservation medicine studies the relationship between human and animal health, and environmental conditions. Also known as ecological medicine, environmental medicine, or medical geology.
Diving medicine (or hyperbaric medicine) is the prevention and treatment of diving-related problems.
Forensic medicine deals with medical questions in legal context, such as determination of the time and cause of death.
Medical humanities includes the humanities (literature, philosophy, ethics, history and religion), social science (anthropology, cultural studies, psychology, sociology), and the arts (literature, theater, film, and visual arts) and their application to medical education and practice.
Medical informatics and medical computer science are relatively recent fields that deal with the application of computers and information technology to medicine.
Nosology is the classification of diseases for various purposes.
Sports medicine deals with the treatment and preventive care of athletics, amateur and professional. The team includes specialty physicians and surgeons, athletic trainers, physical therapists, coaches, other personnel, and, of course, the athlete.

Medical education

See also the main article, Medical doctor (BE) or Physician (AE)

Medical training involves several years of university study followed by several more years of residential practice at a hospital. Entry to a medical degree in some countries (such as the United States) requires the completion of another degree first, while in other countries (such as the United Kingdom, Australia and New Zealand) medical training can be commenced as an undergraduate degree immediately after secondary education.

The name of the medical degree gained at the end varies: some countries (e.g. the US) call it "Doctor of Medicine" (abbreviated 'M.D.'), while other countries (mostly following the British Oxbridge system) call it "Medicinæ Baccalaureus & Baccalaureus Chirurgiæ" (Latin for "Bachelor of Medicine/Bachelor of Surgery", Old English: "Chirurgie"); this is technically a double degree, frequently abbreviated 'MB BChir', 'MB ChB', 'MB BS' (or variations thereof), dependent on the medical school. In either case, graduates of a medical degree may call themselves physician. In the US and some other countries there is a parallel system of medicine called "osteopathy" which awards the degree D.O. (doctor of osteopathy). In many countries, a doctorate of medicine does not require original research as does, in distinction, a Ph.D..

Once graduated from medical school most physicians begin their residency/house post training, where skills in a speciality of medicine are learned, supervised by more experienced doctors. The first year of residency is known as the "intern" year (USA) or "junior/pre-registration house officer" year (UK). The duration of residency training depends on the speciality.

A medical graduate can then enter general practice and become a general practitioner (or primary care internist in the USA); training for these is generally shorter, while specialist training is typically longer.

Legal restrictions

In most countries, it is prohibited by law to practice medicine without a proper degree in that field and doctors must be licensed by a medical board or some other equivalent organization. These laws and regulatory mechanisms reflect the socially agreed definition of practices seen as Western, or Hippocratic Medicine. They are meant as a safeguard against charlatans and those who falsify their educational and profesional background in medicine. These legal restrictions are not designed to interfere with the completely legal activities of practitioners whose practices follow other valid paradigms of health and healing, such as alternative medicine or faith healing.

Criticism

Criticism against medicine has a long history. In the Middle Ages, it was not considered a profession suitable for Christians, as disease was considered Godsent, and interfering with the process a form of blasphemy. Barber-surgeons generally had a bad reputation that was not to improve until the development of academic surgery as a specialism of medicine, rather than an accessory field.

Through the course of the twentieth century, doctors naturally focused increasingly on the technology that was enabling them to make dramatic improvements in patients' health. This resulted in criticism for the loss of compassion and mechanistic, detached treatment. This issue started to reach collective professional consciousness in the 1970s and the profession had begun to respond by the 1980 and 1990s.

Perhaps the most devastating criticism came from Ivan Illich in his 1976 work Medical Nemesis. In his view, modern medicine only medicalises disease, causing loss of health and wellness, while generally failing to restore health by eliminating disease. The human being thus becomes a lifelong patient. Other less radical philosophers have voiced similar views, but none were as virulent as Illich. (Another example can be found in Technopoly: The Surrender of Culture to Technology by Neil Postman, 1992, which criticises overreliance on technological means in medicine.)

Criticism of modern medicine has led to some improvements in the curricula of medical schools, which now teach students systematically on medical ethics, holistic approaches to medicine, the biopsychosocial model and similar concepts.

The inability of modern medicine to properly address many common complaints continues to prompt many people to seek support from alternative medicine. Although most alternative approaches lack scientific validation, many report improvement of symptoms after obtaining alternative therapies.