Renal Clearance

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Renal Clearance

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rubensssss
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04/29/04 - 10:45 PM

FA 2004 page 356

Renal Clearance who can explanit it in English.

Cx=Ux V/P= volume of plasma from which the substance is cleared completely per unit time.

If Cx< GFR, then there is nt tubular reabsrption of X.
If Cx> GFR, then there is net tubular secretion of X.
If Cx =GFR,then there is no net secretion or reabsortion.

What is X?

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Ruben sssss

Idiopathic
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04/29/04 - 11:38 PM

X = a certain solute. For instance, plug in Na+, and you have

CNa+ = UNa+(V)/PNa+

or rather, sodium clearance equals urinary sodium times volume, divided by plasma sodium. As plasma sodium increases, urinary sodium has to increase, or clearance will go down (obviously). This is why, when figuring creatinine clearance, plasma creatinine essentially doubles for every halving of creatining clearance (which equals GFR).

Now, for when clearance does not equal GFR:
If the substance is filtered AND secreted (i.e para-amino hippurate), then its clearance will be GREATER than the GFR (Cx > GFR)

If the substance is filtered and reabsorbed (most everything vital), then its clearance will be LESS than the GFR (Cx < GFR)

In the case of creatinine and inulin, there is essentially no secretion or reabsorption after the filtration has occurred, and these are relatively good markers of GFR, because of this (Cx = GFR)

rubensssss
Forum Guru

Topics: 95
Posts: 451

04/30/04 - 04:43 AM

"Idiopathic" wrote:
X = a certain solute. For instance, plug in Na+, and you have

CNa+ = UNa+(V)/PNa+

or rather, sodium clearance equals urinary sodium times volume, divided by plasma sodium. As plasma sodium increases, urinary sodium has to increase, or clearance will go down (obviously). This is why, when figuring creatinine clearance, plasma creatinine essentially doubles for every halving of creatining clearance (which equals GFR).

Now, for when clearance does not equal GFR:
If the substance is filtered AND secreted (i.e para-amino hippurate), then its clearance will be GREATER than the GFR (Cx > GFR)

If the substance is filtered and reabsorbed (most everything vital), then its clearance will be LESS than the GFR (Cx < GFR)

In the case of creatinine and inulin, there is essentially no secretion or reabsorption after the filtration has occurred, and these are relatively good markers of GFR, because of this (Cx = GFR)

Thanks very much Idiopathic.
In my city Mcallen Texas USA is right now 5:42 am
and I am going to work will back at 3:00 pm. lt me study what you just say.

Thanks very much for your complete explanation.

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Ruben sssss

neb
Forum Newbie

Topics: 2
Posts: 4

05/07/04 - 06:54 PM

hey i didnt clearly understand ur q but i mean it seems u have clearly written it down .x can be any substance that is cleared off plasma and depending on wether it is reabsorbed ,secreted or both filtered and secreted ,the clearance of the substance ,any substance x can be calculated.for more info u can refer board review series it has good explanations on renal phy and pathology. take care.

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neb.

rubensssss
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Topics: 95
Posts: 451

05/08/04 - 10:17 PM

Thanks neb

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Ruben sssss

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