Blood urea nitrogen: Difference between revisions

Blood urea nitrogen
Blood urea nitrogen
	Urea
MeSH	D001806
LOINC	6299-2, 59570-2, 12961-9, 12963-5, 12962-7

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Blood urea nitrogen (BUN) is a medical test that measures the amount of urea nitrogen found in blood. The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain 7 to 18 mg/dL (0.388 to 1 mmol/L) of urea nitrogen.^[1] Individual laboratories may have different reference ranges, as they may use different assays.^[2]^[3]^[4] The test is used to detect kidney problems. It is not considered as reliable as creatinine or BUN-to-creatinine ratio blood studies.^[1]

Interpretation

BUN is an indication of kidney health. The normal range is 2.1–7.1 mmol/L or 6–20 mg/dL.^[1]

The main causes of an increase in BUN are: high-protein diet, decrease in glomerular filtration rate (GFR) (suggestive of kidney failure), decrease in blood volume (hypovolemia), congestive heart failure, gastrointestinal hemorrhage,^[5] fever, rapid cell destruction from infections, athletic activity, excessive muscle breakdown, and increased catabolism.^[1]

Hypothyroidism can cause both decreased GFR and hypovolemia, but BUN-to-creatinine ratio has been found to be lowered in hypothyroidism and raised in hyperthyroidism.

The main causes of a decrease in BUN are malnutrition (low-protein diet), severe liver disease, anabolic state, and syndrome of inappropriate antidiuretic hormone.^[5]

Another rare cause of a decreased BUN is ornithine transcarbamylase deficiency, which is a genetic disorder inherited in an X-linked recessive pattern. OTC deficiency is also accompanied by hyperammonemia and high orotic acid levels.

Units

BUN is usually reported in mg/dL in some countries (e.g. United States, Mexico, Italy, Austria, and Germany). Elsewhere, the concentration of urea is reported in SI units as mmol/L.

$BUN_{mg/dL}$ represents the mass of nitrogen within urea/volume, not the mass of whole urea. Each molecule of urea has two nitrogen atoms, each having molar mass 14 g/mol. To convert from mg/dL of blood urea nitrogen to mmol/L of urea:

$Urea_{mmol/L}=BUN_{mmol/L}=BUN_{mg/dL}*{\frac {10_{dL/L}}{14*2}}=BUN_{mg/dL}*0.3571$

Note that molar concentrations of urea and urea nitrogen are equal, because both nitrogen gas and urea has two nitrogen atoms.

Convert BUN to urea in mg/dL by using following formula:

$Urea_{mg/dL}=BUN_{mg/dL}*{\frac {60}{14*2}}=BUN_{mg/dL}*2.14$

Where 60 represents MW of urea and 14*2 MW of urea nitrogen.

References

^ ^a ^b ^c ^d Lewis, Sharon Mantik; Dirksen, Shannon Ruff; Heitkemper, Margaret M.; Bucher, Linda; Harding, Mariann (5 December 2013). Medical-surgical nursing : assessment and management of clinical problems (9th ed.). St. Louis, Missouri. ISBN 978-0-323-10089-2. OCLC 228373703.{{cite book}}: CS1 maint: location missing publisher (link)
^ Tao Le; Vikas Bhushan; Deepak Rao (2007). First Aid for the USMLE Step 1 2008. New York: McGraw-Hill Medical. Last page. ISBN 978-0-07-149868-5.
^ "Normal Lab Results". Marshal University School of Medicine. Archived from the original on December 16, 2014.
^ "Blood urea nitrogen (BUN) test - Mayo Clinic". www.mayoclinic.org. Retrieved 2019-05-13.
^ ^a ^b Loscalzo, Joseph; Fauci, Anthony S.; Kasper, Dennis L.; Hauser, Stephen; Longo, Dan; Jameson, J. Larry (2022-04-05). Harrison's Principles of Internal Medicine, Twenty-First Edition (Vol.1 & Vol.2). New York: McGraw Hill Professional. p. 611. ISBN 978-1-264-26851-1.

[:1-1] Lewis, Sharon Mantik; Dirksen, Shannon Ruff; Heitkemper, Margaret M.; Bucher, Linda; Harding, Mariann (5 December 2013). Medical-surgical nursing : assessment and management of clinical problems (9th ed.). St. Louis, Missouri. ISBN 978-0-323-10089-2. OCLC 228373703.{{cite book}}: CS1 maint: location missing publisher (link)

[firstaid-2] Tao Le; Vikas Bhushan; Deepak Rao (2007). First Aid for the USMLE Step 1 2008. New York: McGraw-Hill Medical. Last page. ISBN 978-0-07-149868-5.

[Marshall-3] "Normal Lab Results". Marshal University School of Medicine. Archived from the original on December 16, 2014.

[4] "Blood urea nitrogen (BUN) test - Mayo Clinic". www.mayoclinic.org. Retrieved 2019-05-13.

[:0-5] Loscalzo, Joseph; Fauci, Anthony S.; Kasper, Dennis L.; Hauser, Stephen; Longo, Dan; Jameson, J. Larry (2022-04-05). Harrison's Principles of Internal Medicine, Twenty-First Edition (Vol.1 & Vol.2). New York: McGraw Hill Professional. p. 611. ISBN 978-1-264-26851-1.

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[2]

[3]

[4]

[5]

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+{{Short description|Blood test}}
 {{Redirect|BUN|other uses|Bun (disambiguation)}}
 {{Infobox diagnostic
 | Name            = Blood urea nitrogen
 | Image           = Urea-3D-balls.png
 | Alt             =
 | Caption         = [[Urea]]
 | DiseasesDB      =
 | ICD10           =
 | ICD9            =
 | ICDO            =
 | MedlinePlus     =
 | eMedicine       =
 | MeshID          = D001806
 | LOINC           = {{LOINC|6299-2}}, {{LOINC|59570-2}}, {{LOINC|12961-9}}, {{LOINC|12963-5}}, {{LOINC|12962-7}}
 | HCPCSlevel2     =
 | Reference_range =
 }}
-'''Blood urea nitrogen''' ('''BUN''') is a medical test that measures the amount of urea nitrogen found in blood. The liver produces [[urea]] in the [[urea cycle]] as a waste product of the [[digestion]] of [[protein]].  Normal human adult blood should contain between 10 and 50 [[milligram|mg]] of '''urea nitrogen''' per 100 [[milliliter|ml]] (10–50&nbsp;mg/[[deciliter|dL]]) of blood. Individual laboratories will have different [[Reference ranges for blood tests|reference range]]s as the assay used can vary between laboratories.<ref name=firstaid>Last page of {{cite book |author1=Deepak A. Rao |author2=Le, Tao |author3=Bhushan, Vikas |title=First Aid for the USMLE Step 1 2008 (First Aid for the Usmle Step 1) |publisher=McGraw-Hill Medical |location= |year=2007 |pages= |isbn=0-07-149868-0 |oclc= |doi= |accessdate=}}</ref><ref name=Marshall>[http://musom.marshall.edu/usmle/usmlelabvalues.htm Normal Lab Results] {{webarchive |url=https://web.archive.org/web/20141216130827/http://musom.marshall.edu/usmle/usmlelabvalues.htm |date=December 16, 2014 }} from Marshal University School of Medicine</ref>
+'''Blood urea nitrogen''' ('''BUN''') is a medical test that measures the amount of [[urea]] [[nitrogen]] found in blood. The liver produces urea in the [[urea cycle]] as a waste product of the [[digestion]] of [[protein]].  Normal human adult [[blood]] should contain 7 to 18 mg/dL (0.388 to 1 mmol/L) of urea nitrogen.<ref name=":1">{{Cite book|title=Medical-surgical nursing : assessment and management of clinical problems|last1=Lewis|first1=Sharon Mantik|last2=Dirksen|first2=Shannon Ruff|last3=Heitkemper|first3=Margaret M.|last4=Bucher|first4=Linda|last5=Harding|first5=Mariann|date=5 December 2013|isbn=978-0-323-10089-2|edition=9th|location=St. Louis, Missouri|oclc=228373703}}</ref> Individual laboratories may have different [[Reference ranges for blood tests|reference range]]s, as they may use different [[Assay|assays]].<ref name=firstaid>{{cite book|at=Last page|author=Tao Le|author2=Vikas Bhushan|author3=Deepak Rao|title=First Aid for the USMLE Step 1 2008|publisher=McGraw-Hill Medical|location=New York|year=2007|isbn=978-0-07-149868-5|url-access=registration|url=https://archive.org/details/firstaidforusmle00taol}}</ref><ref name=Marshall>{{cite web|url=http://musom.marshall.edu/usmle/usmlelabvalues.htm|title=Normal Lab Results|url-status=dead|archive-url=https://web.archive.org/web/20141216130827/http://musom.marshall.edu/usmle/usmlelabvalues.htm|archive-date=December 16, 2014|publisher=Marshal University School of Medicine}}</ref><ref>{{Cite web|url=https://www.mayoclinic.org/tests-procedures/blood-urea-nitrogen/about/pac-20384821|title=Blood urea nitrogen (BUN) test - Mayo Clinic|website=www.mayoclinic.org|access-date=2019-05-13}}</ref> The test is used to detect [[kidney]] problems. It is not considered as reliable as [[creatinine]] or [[BUN-to-creatinine ratio]] blood studies.<ref name=":1" />
 ==Interpretation==
-BUN is an indication of [[renal]] (kidney) health.  The normal range is 1.8–7.1&nbsp;mmol/[[liter|L]] or 6–20&nbsp;mg/[[deciliter|dL]].
+BUN is an indication of kidney health.  The normal range is 2.1–7.1&nbsp;mmol/[[liter|L]] or 6–20&nbsp;mg/[[deciliter|dL]].<ref name=":1" />
-The main causes of an increase in BUN are: high protein diet, decrease in [[glomerular filtration rate]] (GFR) (suggestive of renal failure) and in blood volume ([[hypovolemia]]), [[congestive heart failure]], gastrointestinal hemorrhage,<ref name=":0">Longo et al., Harrison's Principles of Internal Medicine, 18th ed., p.611</ref> [[fever]], and increased [[catabolism]]. Hypothyroidism can cause both decreased GFR and hypovolemia, but [[BUN-to-creatinine ratio]] has been found to be lowered in hypothyroidism and raised in hyperthyroidism.
+The main causes of an increase in BUN are: high-protein diet, decrease in [[glomerular filtration rate]] (GFR) (suggestive of [[kidney failure]]), decrease in blood volume ([[hypovolemia]]), [[congestive heart failure]], gastrointestinal hemorrhage,<ref name=":0">{{cite book | last=Loscalzo | first=Joseph | last2=Fauci | first2=Anthony S. | last3=Kasper | first3=Dennis L. | last4=Hauser | first4=Stephen | last5=Longo | first5=Dan | last6=Jameson | first6=J. Larry | title=Harrison's Principles of Internal Medicine, Twenty-First Edition (Vol.1 & Vol.2) | publisher=McGraw Hill Professional | publication-place=New York | date=2022-04-05 | isbn=978-1-264-26851-1 | page=611}}</ref> [[fever]], rapid cell destruction from infections, athletic activity, excessive muscle breakdown, and increased [[catabolism]].<ref name=":1" />
+Hypothyroidism can cause both decreased GFR and hypovolemia, but [[BUN-to-creatinine ratio]] has been found to be lowered in hypothyroidism and raised in hyperthyroidism.
-The main causes of a decrease in BUN are severe liver disease, anabolic state, and  [[Syndrome of inappropriate antidiuretic hormone secretion|syndrome of inappropriate antidiuretic hormone]].<ref name=":0" />
+The main causes of a decrease in BUN are malnutrition (low-protein diet), severe liver disease, anabolic state, and  [[Syndrome of inappropriate antidiuretic hormone secretion|syndrome of inappropriate antidiuretic hormone]].<ref name=":0" />
 [[File:Blood values sorted by mass and molar concentration.png|thumb|center|700px|[[Reference ranges for blood tests]], comparing urea (yellow at right) to other blood constituents]]
@@ Line 29: / Line 32: @@
 ==Units==
-BUN (urea-N) is mg/dL in the United States, Mexico, Italy, Austria, and Germany. Elsewhere, the concentration of urea is reported as mmol/L, generally depending on the lab.
+BUN is usually reported in mg/dL in some countries (e.g. United States, Mexico, Italy, Austria, and Germany). Elsewhere, the concentration of urea is reported in SI units as mmol/L.
+<math chem>BUN_{mg/dL}</math> represents the mass of nitrogen within urea/volume, not the mass of whole urea. Each molecule of urea has two nitrogen atoms, each having molar mass 14 g/mol. To convert from mg/dL of blood urea nitrogen to mmol/L of urea:
-BUN (urea-N) SI unit is mmol/L
-BUN [mmol/L] = BUN [mg/dL] * 0.3571
+<math chem>Urea_{mmol/L} = BUN_{mmol/L} = BUN_{mg/dL} * \frac{10_{dL/L}}{14*2} = BUN_{mg/dL} * 0.3571</math>
+Note that molar concentrations of urea and urea nitrogen are equal, because both nitrogen gas and urea has two nitrogen atoms.
-To convert from mg/dL of blood urea nitrogen to mmol/L of urea, multiply by 0.357 (each molecule of urea having two nitrogens, each of molar mass 14g/mol) (BUN is the mass of nitrogen within urea/volume, not the mass of urea)
-::Urea [mmol/L] = BUN [mg/dL of [[nitrogen]]] x 10 [dL/L] / 14x2  [mg N/mmol urea] (the mass of nitrogen within urea is used)
-convert BUN to urea in mg/dL by using following formula:
+Convert BUN to urea in mg/dL by using following formula:
-::Urea [mg/dL]= BUN [mg/dL] * 2.14
+<math chem>Urea_{mg/dL} = BUN_{mg/dL} * \frac{60}{14*2} = BUN_{mg/dL} * 2.14 </math>
-(conversion factor derived by: MW of urea = 60, MW of urea nitrogen = 14x2 => 60/28 = 2.14)
+Where 60 represents MW of urea and 14*2 MW of urea nitrogen.
-factor = 1 for conversions in mmol (1 mole N<sub>2</sub> = 2 moles N per mole of urea):
-::BUN [mmol/L]= urea [mmol/L]
 ==See also==
-*[[Kt/V]]
+* [[Kt/V]]
+* [[Standardized Kt/V]]
-*[[Urea reduction ratio]]
-*[[Urine urea nitrogen]]
+* [[Urea reduction ratio]]
-*[[Standardized Kt/V]]
+* [[Urine urea nitrogen]]
 ==References==
 {{Reflist}}<!--added under references heading by script-assisted edit-->
-==External links==
 {{Blood tests}}
@@ Line 61: / Line 61: @@
 {{DEFAULTSORT:Blood Urea Nitrogen}}
 [[Category:Chemical pathology]]
+[[Category:Diagnostic nephrology]]
 [[Category:Nitrogen cycle]]
-[[Category:Nephrology]]