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The fractional excretion of sodium (FE Na) is the percentage of the sodium filtered by the kidney which is excreted in the urine. It is measured in terms of plasma and urine sodium , rather than by the interpretation of urinary sodium concentration alone, as urinary sodium concentrations can vary with water reabsorption .
The renal clearance ratio or fractional excretion is a relative measure of the speed at which a constituent of urine passes through the kidneys. [ 1 ] [ 2 ] It is defined by following equation: c l e a r a n c e r a t i o o f X = C x C i n {\displaystyle clearance\ ratio\ of\ X={\frac {C_{x}}{C_{in}}}}
The urine sodium is expressed as a concentration (such as millimoles per liter). The result must therefore be interpreted in the context of the degree of urine concentration present. Alternatively, the urine sodium can be standardized to the excretion of creatinine using a formula such as the fractional excretion of sodium (FENa).
In renal physiology, the filtration fraction is the ratio of the glomerular filtration rate (GFR) over the renal plasma flow (RPF).. Filtration Fraction, FF = GFR/RPF, or =. ...
The "Hepatic Extraction Ratio" is a similar measurement for clearance of a substance (usually a pharmacological drug) by the liver. It is defined as the fraction of drug removed from blood by the liver, and depends on 3 factors— the hepatic blood flow, the uptake into the hepatocytes, and the enzyme metabolic capacity.
A sodium-related parameter is fractional sodium excretion, which is the percentage of the sodium filtered by the kidney which is excreted in the urine. It is a useful parameter in acute kidney failure and oliguria , with a value below 1% indicating a prerenal disease and a value above 1% suggesting acute tubular necrosis or other kidney damage.
Usually, clearance is measured in L/h or mL/min. [2] Excretion, on the other hand, is a measurement of the amount of a substance removed from the body per unit time (e.g., mg/min, μg/min, etc.). While clearance and excretion of a substance are related, they are not the same thing.
It uses Na-H antiport, Na-glucose symport, sodium ion channels (minor). [1] It is stimulated by angiotensin II and aldosterone, and inhibited by atrial natriuretic peptide. It is very efficient, since more than 25,000 mmol/day of sodium is filtered into the nephron, but only ~100 mmol/day, or less than 0.4% remains in the final urine.