Extraction ratio
Encyclopedia
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.
Measured in concentration in blood plasma
, it may thus be expressed as:
, where Pa is the concentration in renal artery
, and Pv is the concentration in the renal vein
.
For instance, para aminohippuric acid (PAH) is almost completely excreted in the final urine, and thus almost none is found in the venous return (Pv ~0). Therefore, the extraction ration of PAH ~1. This is why PAH is used in PAH clearance
to estimate renal plasma flow.
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;...
, primarily used to calculate renal plasma flow in order to evaluate 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...
. It is the amount of compound entering the kidney that got excreted into the final urine.
Measured in concentration in blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
, it may thus be expressed as:
, where Pa is the concentration in renal artery
Renal artery
The renal arteries normally arise off the side of the abdominal aorta, immediately below the superior mesenteric artery, and supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle with the aorta....
, and Pv is the concentration in the renal vein
Renal vein
The renal veins are veins that drain the kidney. They connect the kidney to the inferior vena cava.It is usually singular to each kidney, except in the condition "multiple renal veins".It also divides into 2 divisions upon entering the kidney:...
.
For instance, para aminohippuric acid (PAH) is almost completely excreted in the final urine, and thus almost none is found in the venous return (Pv ~0). Therefore, the extraction ration of PAH ~1. This is why PAH is used in PAH clearance
PAH clearance
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....
to estimate renal plasma flow.