View source for Rec. 709

<div style="float:right;border:solid 10px white;">{{Renal worksheet}}</div>
'''Para aminohippurate clearance''' or '''PAH clearance''' is a method used in [[renal physiology]] to measure [[renal plasma flow]], which, in turn, is a measure of [[renal function]].

The concentration of [[para aminohippurate]] (PAH) is measured in one [[arterial blood sample]] (P<sub>PAH</sub>) and one urine sample(U<sub>PAH</sub>). The [[Urine flow rate|urine flow]] (V) is also measured. Renal perfusion flow is then calculated by:

:<math>RPF = \frac{U_{PAH}}{P_{PAH}} V</math>

What in fact is calculated is the [[effective renal plasma flow]] (eRPF). However, since the renal [[extraction ratio]] of PAH almost equals 1, then eRPF almost equals RPF.

==Precision==
The renal [[extraction ratio]] of PAH in a normal individual is approximately 0.92,<ref>{{cite journal |author=Reubi FC |title=Glomerular filtration rate, renal blood flow and blood viscosity during and after diabetic coma |journal=Circulation Res. |volume=1 |issue=5 |pages=410–3 |date=September 1953 |pmid=13082682 |doi= |url=http://circres.ahajournals.org/cgi/reprint/1/5/410.pdf|format=PDF}}</ref> and thus not exactly 1.0. Thus, this method usually underestimates RPF by approximately 10%. This margin of error is generally acceptable considering the ease with which eRPF is measured.

==See also==
* [[Renal blood flow]]

==References==
{{reflist}}

==External links==
* [http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v02/020586r00.htm Renal Clearance Techniques]

{{renal physiology}}

{{DEFAULTSORT:Pah Clearance}}
[[Category:Renal physiology]]
[[Category:Blood tests]]