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A '''medical sign''' is an [[Objectivity (science)|objective]]<ref>[http://www.emedicine.com/asp/dictionary.asp?keyword=sign eMedicine/Stedman Medical Dictionary Lookup!<!-- Bot generated title -->]{{Clarify me|date=February 2009|reason=This is not a proper reference citation. Use [[Template:Cite web]] to provide source details.}}</ref> indication of some medical fact or characteristic that may be detected by a [[physician]] during a [[physical examination]] of a [[patient]].<ref>[http://www.uwo.ca/pathol/glossary.html#S Definition] at [[University of Western Ontario]]{{Clarify me|date=February 2009|reason=This is not a proper reference citation. Use [[Template:Cite web]] to provide source details.}}</ref>

Signs may have no meaning for, or even be noticed by, the patient, but may be full of meaning for the healthcare provider, and are often significant in assisting a healthcare provider in [[medical diagnosis|diagnosis]] of medical condition(s) responsible for the patient's [[symptom]]s.

Examples include [[hypertension|elevated blood pressure]], a [[Nail clubbing|clubbing]] of the fingers (which may be a sign of lung disease, or many other things), and [[arcus senilis]].

The term ''sign'' is not to be confused with the term ''[[Indication (medicine)|indication]]'', which denotes a valid reason for using some treatment.

==Signs and semiotics==
The art of interpreting clinical signs was originally called ''semiotics'' (a term now used for [[Semiotics|the study of sign communication in general]]) in English. This term, then spelt ''semeiotics'' (derived from the Greek adjective σημειοτικός: ''semeiotikos'', "to do with signs"), was first used in English in 1670 by [[Henry Stubbes]] (1631&ndash;1676), to denote the branch of medical science relating to the interpretation of signs:

:''…nor is there any thing to be relied upon in Physick, but an exact knowledge of medicinal phisiology (founded on observation, not principles), semeiotics, method of curing, and tried (not excogitated, not commanding) medicines…''<ref>Stubbe, H. ([[Henry Stubbes]]), ''The Plus Ultra reduced to a Non Plus: Or, A Specimen of some Animadversions upon the Plus Ultra of Mr. Glanvill, wherein sundry Errors of some Virtuosi are discovered, the Credit of the Aristotelians in part Re-advanced; and Enquiries made...'', (London), 1670, p. 75</ref>

==Eponymous signs==
{{main|List of eponymous medical signs}}
Historically, medical signs were [[Eponym|named after]] the [[physician]]s who first described them.<ref>See [[list of eponymous medical signs]], and "Who Named It?" [http://www.whonamedit.com/azeponyms.cfm] for more information on eponymous signs.</ref>

==Signs versus symptoms==
Signs are different from symptoms, the ''subjective'' experiences, such as [[fatigue (physical)|fatigue]], that patients might report to their examining physician.

For convenience, signs are commonly distinguished from symptoms as follows: Both are something abnormal, relevant to a potential medical condition, but a ''symptom'' is experienced and reported by the patient, while a ''sign'' is discovered by the physician during examination of the patient.<ref name="King 1982">{{Cite book |author=King, Lester S. |title=Medical Thinking: A Historical Preface |publisher=Princeton University Press |location=Princeton, NJ |year=1982 |isbn=0691082979}}</ref>{{rp|75}}

A slightly different definition views signs as any indication of a medical condition that can be objectively observed (i.e., by someone other than the patient), whereas a symptom is merely any manifestation of a condition that is apparent to the patient (i.e., something consciously affecting the patient).  From this definition, it can be said that an asymptomatic patient is uninhibited by disease.  However, a doctor may discover the sign hypertension in an asymptomatic patient, who does not experience "dis-ease", and the sign indicates a disease state that poses a hazard to the patient.  With this set of definitions, there is some overlap &ndash; certain things may qualify as both a sign and a symptom (e.g., a bloody nose).

Lester S. King, author of ''Medical Thinking'', argues that an "essential feature" of a sign is that there is both a sign [or "signifier"] and a "thing signified". And, because "the essence of a sign is to convey information", it can only be a sign, properly speaking, if it has meaning. Therefore, "a sign ceases to be a sign when you cannot read it".<ref name="King 1982" />{{rp|73&ndash;74}} A person, who has and exercises the knowledge required to understand the significance or indication or meaning of the sign, is necessary for something to be a complete sign. A physical phenomenon that is not actually interpreted as a sign pointing to something else is, in medicine, merely a symptom. Thus, King rejects "these present-day views [distinguishing signs from symptoms based on patient-subjective versus clinician-objective], however widely accepted, as quite faulty, at variance not only with ordinary usage but with the entire history of medicine."<ref name="King 1982" />{{rp|77}}

==Types of signs==

Medical signs may be classified by the type of inference that may be made from their presence,<ref name="King 1982" />{{rp|80&ndash;81}} for example:

* '''[[Prognostic]] signs''' (from ''progignṓskein'', προγιγνώσκειν, "to know beforehand"): signs that indicate the outcome of the current bodily state of the patient (i.e., rather than indicating the name of the disease). Prognostic signs always point to the future. Perhaps the most famous prognostic sign is the [[facies Hippocratica]]:

<blockquote>"[If the patient's facial] appearance may be described thus: the nose sharp, the eyes sunken, the temples fallen in, the ears cold and drawn in and their lobes distorted, the skin of the face hard, stretched and dry, and the colour of the face pale or dusky.… and if there is no improvement within [a prescribed period of time], it must be realized that this sign portends death."<ref name="Chadwick 1978">{{cite book |author=Chadwick, J. & Mann, W.N.(trans.) |title=Hippocratic writings |publisher=Penguin |location=Harmondsworth, UK |year=1978 |pages=170&ndash;171 |isbn=0-14-044451-3 |oclc= |doi=}}</ref></blockquote>

* '''[[Anamnestic]] signs''' (from ''anamnēstikós'', ἀναμνηστικός, "able to recall to mind"): signs that (taking into account the current state of a patient's body), indicate the past existence of a certain disease or condition. Anamnestic signs always point to the ''past''. (Whenever we see a man walking with a particular gait, with one arm paralysed in a particular way, we say "This man has had a stroke"; and, if we see a woman in her late 50s with one arm distorted in a particular way, we say "She had polio as a child".){{Dubious|date=December 2008|reason=Very, very oversimplistic, phrased non-encyclopedically (who is "we"?), and reads like it was copyright-violatingly lifted from someone else's book.}}

* '''[[medical diagnosis|Diagnostic]] signs''' (from ''diagnōstikós'', διαγνωστικός, "able to distinguish"): signs that lead to the recognition and identification of a disease (i.e., they indicate the '''name''' of the disease).

* '''[[Pathognomonic]] signs''' (from ''pathognomonikós'', παθογνωμονικός, "skilled in diagnosis", derived from ''páthos'', πάθος, "suffering, disease", and ''gnṓmon'', γνώμον, "judge, indicator"): the particular signs whose presence means, beyond any doubt, that a particular disease is present. They represent a marked intensification of a diagnostic sign. (An example would be the palmar [[xanthoma]]ta seen on the hands of people suffering from [[hyperlipoproteinaemia]].) Singular pathognomonic signs are relatively uncommon.

<blockquote>"[Thus] a symptom is a phenomenon, caused by an illness and observable directly in experience. We may speak of it as a '''manifestation''' of illness. When the observer reflects on that phenomenon and uses it as a base for further inferences, then that symptom is transformed into a sign. As a sign it points beyond itself — perhaps to the present illness, or to the past or to the future. That to which a sign points is part of its meaning, which may be rich and complex, or scanty, or any gradation in between. In medicine, then, a sign is thus a phenomenon from which we may get a message, a message that tells us something about the patient or the disease. A phenomenon or observation that does not convey a message is not a sign. The distinction between signs and symptom rests on the meaning, and this is not perceived but inferred."<ref name="King 1982" />{{Rp|81}}</blockquote>

==Technological development creating signs detectable only by physicians==
Prior to the nineteenth century there was little difference in the powers of observation between physician and patient. Most medical practice was conducted as a joint co-operative interaction between the physician and the patient as equals.<ref name="Jewson 1974">Jewson, N. D., "[http://soc.sagepub.com/cgi/content/abstract/8/3/369 Medical Knowledge and the Patronage System in 18th Century England]", ''Sociology'', Vol.8, No.3, (1974), pp. 369&ndash;385.</ref><ref name="Jewson 1976">Jewson, N. D., "[http://soc.sagepub.com/cgi/content/abstract/10/2/225 The Disappearance of the Sick Man from Medical Cosmology, 1770&ndash;1870]", ''Sociology'', Vol.10, No.2, (1976), pp. 225&ndash;244.</ref> Whilst each noticed much the same things, the physician had a more informed interpretation of those things: "the physicians knew what the findings meant and the layman did not".<ref name="King 1982" />{{rp|82}}

===Advances in the 19th century===
However, the patient was gradually removed from the medical interaction<ref name="Jewson 1974" /><ref name="Jewson 1976" /><ref name="pmid3413276">{{cite journal |author=Tsouyopoulos N |title=The mind-body problem in medicine (the crisis of medical anthropology and its historical preconditions) |journal=Hist Philos Life Sci |volume=10 Suppl |issue= |pages=55–74 |year=1988 |pmid=3413276 |doi=}}</ref> due to significant technological advances such as:

* The 1808 introduction of the [[percussion (medicine)|percussion]] technique:
{{cquote2|"The process through which "the physician can assess the state of the underlying lung by sensing the character of vibrations by gentle taps on the chest wall [something which] greatly facilitated the diagnosis of pneumonia and other respiratory diseases" <ref name="Weatherall">{{cite book |author=Weatherall, D. |title=Science and the Quiet Art: The Role of Medical Research in Health Care |publisher=W. W. Norton & Company |location=New York |year= 1996|pages=46 |isbn=0-393-31564-9 |oclc= |doi=}}</ref>}}

The techniques, which had been first described by the Viennese physician [[Leopold Auenbrugger]] (1722&ndash;1809) in 1761, became far more widely known following the publication of [[Jean-Nicolas Corvisart]]'s translation{{Clarify me|date=December 2008|reason=Into what? The translator's name suggests French, but this being en.wiki, the implication to the reader is English.}} of Auenbrugger's work in 1808.

* The 1819 introduction by [[René Laënnec]] (1781&ndash;1826) of the technique of [[auscultation]] (using a [[stethoscope]] to listen to the circulatory and respiratory functions of the body). Laënnec's publication was translated into English, 1821&ndash;1834, by [[John Forbes (physician)|John Forbes]].

* The 1846 introduction by surgeon [[John Hutchinson]] (1811&ndash;1861) of the [[spirometer]], an apparatus for assessing the mechanical properties of the lungs via measurements of forced exhalation and forced inhalation. (The recorded [[lung volumes]] and air flow rates are used to [[Spirometry|distinguish between]] restrictive disease (in which the lung volumes are decreased: e.g., [[cystic fibrosis]]) and obstructive diseases (in which the lung volume is normal but the air flow rate is impeded; e.g., [[emphysema]]).)

* The 1851 invention by [[Hermann von Helmholtz]] (1821&ndash;1894) of the [[ophthalmoscope]], which allowed physicians to examine the inside of the human eye. 

* The 1895 clinical use of [[X-ray]]s which began almost immediately after they had been discovered that year by [[Wilhelm Conrad Röntgen]] (1845&ndash;1923).

* The 1896 introduction of the [[sphygmomanometer]], designed by [[Scipione Riva-Rocci]] (1863&ndash;1937), to measure [[blood pressure]].

===Alteration of the relationship between physician and patient===
The introduction of the techniques of percussion and auscultation into medical practice altered the relationship between physician and patient in a very significant way, specifically because these techniques relied almost entirely upon the physician listening{{Fact|date=February 2009}}.

Not only did this greatly reduce the patient's capacity to observe and contribute to the process of diagnosis, it also meant that the patient was often instructed to stop talking, and remain silent.

As these sorts of evolutionary changes continued to take place in medical practice, it was increasingly necessary to uniquely identify data that was accessible only to the physician, and to be able to differentiate those observations from others that were also available to the patient, and it just seemed natural to use "signs" for the class of physician-specific data, and "symptoms" for the class of observations available to the patient.

King proposes a more advanced notion; namely, that a sign is something that has meaning, regardless of whether it is observed by the physician or reported by the patient:
<blockquote>''The belief that a symptom is a subjective report of the patient, while a sign is something that the physician elicits, is a 20th-century product that contravenes the usage of two thousand years of medicine. In practice, now as always, the physician makes his judgments from the information that he gathers. The modern usage of signs and symptoms emphasizes merely the source of the information, which is not really too important. Far more important is the use that the information serves. If the data, however derived, lead to some inferences and go beyond themselves, those data are signs. If, however, the data remain as mere observations without interpretation, they are symptoms, regardless of their source. Symptoms become signs when they lead to an interpretation. The distinction between information and inference underlies all medical thinking and should be preserved."<ref name="King 1982" />{{rp|89}}</blockquote>

==Signs as tests==
In some senses, the process of diagnosis is always a matter of assessing the ''likelihood'' that a given condition is present in the patient. In a patient who presents with [[haemoptysis]] (coughing up blood), the haemoptysis is very much more likely to be caused by respiratory disease than by the patient having broken their toe. Each question in the history taking allows the medical practitioner to narrow down their view of the cause of the symptom, testing and building up their hypotheses as they go along.

Examination, which is essentially looking for clinical signs, allows the medical practitioner to see if there is evidence in the patient's body to support their hypotheses about the disease that might be present.

A patient who has given a good story to support a diagnosis of [[tuberculosis]] might be found, on examination, to show signs that lead the practitioner away from that diagnosis and more towards [[sarcoidosis]], for example. Examination for signs ''tests'' the practitioner's hypotheses, and each time a sign is found that supports a given diagnosis, that diagnosis becomes more likely.

Special tests (blood tests, [[radiology]], scans, a [[biopsy]], etc.) also allow a hypothesis to be tested. These special tests are also said to show signs in a clinical sense. Again, a test can be considered pathognonomic for a given disease, but in that case the test is generally said to be "diagnostic" of that disease rather than pathognonomic. An example would be a history of a fall from a height, followed by a lot of pain in the leg. The signs (a swollen, tender, distorted lower leg) are only very strongly suggestive of a fracture; it might not actually be broken, and even if it is, the particular kind of fracture and its degree of dislocation need to be known, so the practitioner orders an x-ray. The x-ray film shows a fractured [[tibia]], so the film is said to be diagnostic of the fracture.

==Examples of signs==
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{{col-break}}
* [[Ascites]] (fluid in the abdomen)
* [[Cachexia]] (loss of weight, muscle atrophy)
* [[Caput medusae]] (dilated umbilical veins)
* [[Nail clubbing|Clubbing]] (deformed nails)
* [[Cough]]
* [[Death rattle]] (last moments of life in a person/animal)
* [[Fever]] 
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* [[Gynecomastia]] (excessive breast tissue in males)
* [[Hemoptysis]] (blood-stained sputum)
* [[Hepatosplenomegaly]] (enlarged liver and spleen)
* [[Icterus (medicine)|Icterus]] ("jaundice")
* [[Lymphadenopathy]] (swollen lymph nodes)
* [[Palmar erythema]] (reddening of hands)
* [[Splenomegaly]] (enlarged spleen)
{{col-end}}

==See also==
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{{col-break}}
* [[Symptom]]
* [[Stethoscope]]
* [[Radiologic sign]]
* [[neurological sign]]
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==References==
{{reflist|2}}

==External links==
* Who Named It?[http://www.whonamedit.com/azeponyms.cfm]: eponymous signs.

{{Symptoms and signs}}

[[Category:Medical signs|*]]

[[ast:Signu clínicu]]
[[ca:Signe clínic]]
[[cs:Klinický příznak]]
[[et:Meditsiinisemiootika]]
[[es:Signo clínico]]
[[fr:Signe clinique]]
[[io:Medikala signo]]
[[it:Segno (medicina)]]
[[nl:Klinisch beeld]]
[[no:Sykdomstegn]]
[[pl:Obraz kliniczny]]
[[pt:Sinal (saúde)]]
[[ru:Медицинская семиотика]]
[[sr:Знаци болести]]
[[sv:Fynd (diagnostik)]]
[[th:อาการแสดง]]
[[Category:2Fix]]