Template:Short description Template:Redirect Template:Infobox diagnostic 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">Template:Cite book</ref> Individual laboratories may have different reference ranges, as they may use different assays.<ref name=firstaid>Template:Cite book</ref><ref name=Marshall>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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" />
InterpretationEdit
BUN is an indication of kidney health. The normal range is 2.1–7.1 mmol/L or 6–20 mg/dL.<ref name=":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,<ref name=":0">Template:Cite book</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 malnutrition (low-protein diet), severe liver disease, anabolic state, and syndrome of inappropriate antidiuretic hormone.<ref name=":0" />
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.
UnitsEdit
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:
<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.
Convert BUN to urea in mg/dL by using following formula:
<math chem>Urea_{mg/dL} = BUN_{mg/dL} * \frac{60}{14*2} = BUN_{mg/dL} * 2.14 </math>
Where 60 represents MW of urea and 14*2 MW of urea nitrogen.
See alsoEdit
ReferencesEdit