PAH clearance
Encyclopedia
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 (PPAH) and one urine sample(UPAH). The urine flow
(V) as also measured. Renal perfusion flow is then calculated by:
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.
of PAH in a normal individual is approximately 0.92, 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.
Renal physiology
Renal physiology is the study of the physiology of the kidney. This encompasses all functions of the kidney, including reabsorption of glucose, amino acids, and other small molecules; regulation of sodium, potassium, and other electrolytes; regulation of fluid balance and blood pressure;...
to measure renal plasma flow, which, in turn, is a measure of renal function
Renal function
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...
.
The concentration of para aminohippurate (PAH) is measured in one arterial blood sample (PPAH) and one urine sample(UPAH). The urine flow
Urine flow rate
Urine flow rate is a measure of the quantity of urine produced in a specified period of time. Common periods of time used include "minute" and "24 hours"....
(V) as also measured. Renal perfusion flow is then calculated by:
What in fact is calculated is the effective renal plasma flow
Effective renal plasma flow
Effective renal plasma flow is a measure used in renal physiology to calculate renal plasma flow and hence estimate renal function. eRPF = RPF \times extraction ratio...
(eRPF). However, since the renal extraction ratio
Extraction ratio
Extraction ratio is a measure in renal physiology, primarily used to calculate renal plasma flow in order to evaluate renal function. It is the amount of compound entering the kidney that got excreted into the final urine....
of PAH almost equals 1, then eRPF almost equals RPF.
Precision
The renal extraction ratioExtraction ratio
Extraction ratio is a measure in renal physiology, primarily used to calculate renal plasma flow in order to evaluate renal function. It is the amount of compound entering the kidney that got excreted into the final urine....
of PAH in a normal individual is approximately 0.92, 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.