Editing Dehydration (section)

==Diagnosis==
=== Definition ===
Dehydration occurs when water intake does not replace [[free water clearance|free water]] lost due to normal physiologic processes, including [[breathing]], [[urination]], [[perspiration]], or other causes, including [[diarrhea]], and [[vomiting]]. Dehydration can be life-threatening when severe and lead to [[seizure]]s or respiratory arrest, and also carries the risk of [[osmotic cerebral edema]] if [[Fluid replacement|rehydration]] is overly rapid.<ref>{{EMedicine|article|906999|Dehydration}}</ref>

The term "dehydration" has sometimes been used incorrectly as a proxy for the separate, related condition of [[hypovolemia]], which specifically refers to a decrease in volume of [[blood plasma]].<ref name="Mange K 1997"/> The two are regulated through independent mechanisms in humans;<ref name="Mange K 1997"/> the distinction is important in guiding treatment.<ref name="Bhave G 2011">{{cite journal | vauthors = Bhave G, Neilson EG | title = Volume depletion versus dehydration: how understanding the difference can guide therapy | journal = American Journal of Kidney Diseases | volume = 58 | issue = 2 | pages = 302–309 | date = August 2011 | pmid = 21705120 | pmc = 4096820 | doi = 10.1053/j.ajkd.2011.02.395 }}</ref>

=== Physical examination ===
[[File:UOTW 59 - Ultrasound of the Week 1.webm|thumb|Ultrasound of the blood vessels of the neck that supports the diagnosis of severe dehydration<ref>
{{cite web|title=UOTW#59 - Ultrasound of the Week|url=https://www.ultrasoundoftheweek.com/uotw-59/|website=Ultrasound of the Week|access-date=27 May 2017|date=23 September 2015}}</ref>|229x229px]]Common exam findings of dehydration include dry mucous membranes, dry axillae, increased capillary refill time, sunken eyes, and poor [[skin turgor]].<ref>{{Cite journal | vauthors = Huffman GB |date=1999-09-15 |title=Establishing a Bedside Diagnosis of Hypovolemia |url=https://www.aafp.org/pubs/afp/issues/1999/0915/p1220a.html |journal=American Family Physician |language=en-US |volume=60 |issue=4 |pages=1220–1225}}</ref><ref name = "Hooper_2015" /> More extreme cases of dehydration can lead to orthostatic hypotension, dizziness, weakness, and altered mental status.<ref>{{Cite journal | vauthors = Braun MM, Barstow CH, Pyzocha NJ |date=2015-03-01 |title=Diagnosis and Management of Sodium Disorders: Hyponatremia and Hypernatremia |url= https://www.aafp.org/pubs/afp/issues/2015/0301/p299.html#:~:text=33-,DIAGNOSTIC%20APPROACH,sodium%20gain%20(Table%202).&text=Patients%20are%20often%20asymptomatic%20but,12%20(Figure%20335%20). |journal=American Family Physician |language=en-US |volume=91 |issue=5 |pages=299–307|pmid=25822386 }}</ref> Depending on the underlying cause of dehydration, other symptoms may be present as well. Excessive sweating from exercise may be associated with muscle cramps. Patients with gastrointestinal water loss from vomiting or diarrhea may also have fever or other systemic signs of infection.

The skin [[Turgor pressure|turgor]] test can be used to support the diagnosis of dehydration. The skin turgor test is conducted by pinching skin on the patient's body, in a location such as the forearm or the back of the hand, and watching to see how quickly it returns to its normal position. The skin turgor test can be unreliable in patients who have reduced skin elasticity, such as the elderly.<ref>{{Cite book | vauthors = Thomas J, Monaghan T |url= https://books.google.com/books?id=PF-yAwAAQBAJ |title=Oxford Handbook of Clinical Examination and Practical Skills |date=2014 |publisher=Oxford University Press |isbn=978-0-19-959397-2 |language=en}}</ref>

=== Laboratory tests ===
While there is no single gold standard test to diagnose dehydration, evidence can be seen in multiple laboratory tests involving blood and urine. Serum osmolarity above 295 mOsm/kg is typically seen in dehydration due to free water loss.<ref name = "Hooper_2015" /> A urinalysis, which is a test that performs chemical and microscopic analysis of urine, may find darker color or foul odor with severe dehydration.<ref>{{Cite book | vauthors = Hughes G |title=A medication guide to internal medicine tests and procedures |date=2021 |publisher=Elsevier, Inc |isbn=978-0-323-79007-9 |edition=First |location=Philadelphia}}</ref> Urinary sodium also provides information about the type of dehydration. For hyponatremic dehydration, such as from vomiting or diarrhea, urinary sodium will be less than 10&nbsp;mmol/L due to increased sodium retention by the kidneys in an effort to conserve water.<ref>{{Citation |last=Tietze |first=Karen J. |title=Review of Laboratory and Diagnostic Tests |date=2012 |work=Clinical Skills for Pharmacists |pages=86–122 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780323077385100055 |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-323-07738-5.10005-5 |isbn=978-0-323-07738-5}}</ref> In dehydrated patients with sodium loss due to diuretics or renal dysfunction, urinary sodium may be elevated above 20&nbsp;mmol/L.<ref>{{Cite journal |last1=Yun |first1=Giae |last2=Baek |first2=Seon Ha |last3=Kim |first3=Sejoong |date=2023-05-01 |title=Evaluation and management of hypernatremia in adults: clinical perspectives |journal=The Korean Journal of Internal Medicine |language=en |volume=38 |issue=3 |pages=290–302 |doi=10.3904/kjim.2022.346 |issn=1226-3303 |pmc=10175862 |pmid=36578134}}</ref> Patients may also have elevated serum levels of [[blood urea nitrogen]] (BUN) and [[creatinine]]. Both of these molecules are normally excreted by the kidney, but when the circulating blood volume is low, the kidney can become injured.<ref>{{Cite journal |last1=Mohamed |first1=Mohamed Saied |last2=Martin |first2=Andrew |date=May 2024 |title=Acute kidney injury in critical care |url=https://linkinghub.elsevier.com/retrieve/pii/S1472029924000456 |journal=Anaesthesia & Intensive Care Medicine |language=en |volume=25 |issue=5 |pages=308–315 |doi=10.1016/j.mpaic.2024.03.008}}</ref> This causes decreased kidney function and results in elevated BUN and creatinine in the serum.<ref>{{Citation |last1=Amin |first1=Rasheda |title=Kidney and urinary tract disorders |date=2021 |work=Biochemical and Molecular Basis of Pediatric Disease |pages=167–228 |url=https://linkinghub.elsevier.com/retrieve/pii/B978012817962800010X |access-date=2024-11-06 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-817962-8.00010-x |isbn=978-0-12-817962-8 |last2=Ahn |first2=Sun-Young |last3=Moudgil |first3=Asha}}</ref> {{Further|Portsmouth sign}}