# Talk:Fractional sodium excretion

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## Untitled

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

## to add in the future.

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 $\mathrm{BMI} = \frac{\mathit{weight} \ \mathrm{(lb)}*703}{\mathit{height}^2 (\mathrm{in^2})}$ $\mathrm{BMI} = \frac{\mathit{weight} \ \mathrm{(lb)}*4.88}{\mathit{height}^2 (\mathrm{ft^2})}$

24.43.8.159 (talk) 04:16, 16 March 2009 (UTC)

## Why not urine concentration alone

This is incorrect: "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"

To fix the fact that urinary concentrations vary with water reabsoption, you need to get urinary flow. Plasma concentration has nothing to do with adjusting for this variation. —Preceding unsigned comment added by 87.194.220.146 (talk) 15:03, 21 April 2011 (UTC)

I am completely new to this subject and felt that the article assumes that the reader has a medical backgound and that some elaboration would help the lay reader.

From the article I inferred that sodium excretion in the kidney is a two stage process, glomerular filtration followed by reabsorbtion. The fractional excretion rate is a measure of the effectiveness of the reabsorbion stage. The glomerular filtration rate is assumed to be the same for sodium as for creatinine. I would have liked to see some justification for this assumption. There is also an assumption that there is no reabsorbtion of creatinine. Given these assumptions the rest follows fairly clearly. The interpretation section then implies that virtually all sodium should be reabsorbed, anything less than 99 percent of sodium being reabsorbed implies a pathological condition. However, the first section refers to a stimulus to conserve sodium, which suggests that there might be situations in which a higher FENa might be desirable.

Finally, some actual figures would be helpful, as they might make it possible to relate the article to actual sodium intake, although there are presumably other mechanisms for sodium excretion. Sweating comes to mind.

The table given at the start of the article is completely useless, as the figures are given without units (this should never happen, EVER.) and the abbreviations are not explained. Chrisbaarry (talk) 06:56, 5 October 2011 (UTC)