Talk:Fractional excretion of sodium

I'm just learning those concept so I may be wrong...

In this article, the mathematical equation seems right, but I don't see how to relate the two "other" way of computing FE (that are discuss in text just before the equation). The fractional excretion value are a percentage (no unit) but the two suggested way have units :

(1) "FENa can be calculated by multiplying the plasma sodium concentration by the glomerular filtration rate"

GFR (ml/min) X [Na]plasma (mmol/ml) = mmol/min

(2) "It may also be calculated by multiplying the urine sodium concentration by the urinary flow rate"

[Na]urine (mmol/ml) X Vurine (ml/min) = mmol/min

Could you explain more in detailled how those way of computing the FE are good ? is there an approximation somewhere that is not discuss ?

thank you

Formula

Use something like what they have for BMI changing the wording of course.

SI units	$\mathrm {BMI} ={\frac {{\mathit {weight}}\ \mathrm {(kg)} }{{\mathit {height}}^{2}(\mathrm {m^{2}} )}}$
UK/US units	$\mathrm {BMI} ={\frac {{\mathit {weight}}\ \mathrm {(lb)} *703}{{\mathit {height}}^{2}(\mathrm {in^{2}} )}}$
	$\mathrm {BMI} ={\frac {{\mathit {weight}}\ \mathrm {(lb)} *4.88}{{\mathit {height}}^{2}(\mathrm {ft^{2}} )}}$

--Doc James (talk · contribs · email) 03:48, 16 March 2009 (UTC)