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Old 06-29-2013
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Kidney Thiazides in nephrogenic diabetes insipidus

How does thiazides work in nephrogenic diabetes insipidus ?
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Old 06-29-2013
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This is actually one of my favorite concepts!!

Recall that the Thick Ascending Loop is where you have Free Water (which is water that is no longer associated with salt)

Now under normal physiologic conditions, that free water is dependent on the function of ADH to allow for its reabsorption.

In DI (nephrogenic), the ADH receptors are non-functional. So as you know, that's why you lose all that free water (which can be up to 10L of dilute urine per day!!!!!). Because you lose all this water, your serum osmolarity will increase.

So how to combat this?

Thiazide Diuretics!

1) the thiazide will block the Na/Cl cotransporter...therefore, the Na is excreted with the urine. this makes the urine 'less dilute' than it was before the treatment.

2) Plasma volume will be reduced (this is what thiazide diuretics do)

3) therefore GFR will go down

4) glomerulotubelar feedback ---> Because GFR goes down, that means PT reabsorption of Na and WATER will go up!!! (this is good, because now the DI patient can reabsorb water where he actually can (in the PT)...and it leaves less burden on the part of the kidney where the patient cannot (distal tubule)

Last edited by ReggieMiller; 06-29-2013 at 06:58 AM.
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Old 06-29-2013
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also, remember that thiazides have weak diuretic action (because it has less Na to work with), which is why you wouldn't exacerbate the Nephrogenic DI too much. but the kaplan videos lecturer that if it does happen acutely, then aldosterone would be increasaed, and that would have the potential to reabsorb the 'water' (which, thanks to the thiazide, is no longer free)
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Old 06-29-2013
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Then why can't we use loops ?
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Old 06-29-2013
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Quote:
Originally Posted by dr,maps View Post
Then why can't we use loops ?
i may be wrong, but i think the key difference is that Thiazides are a weaker diuretic. having less Na to work on, will place a limit as to exercabating the Nephrogenic DI. wheresa the LOOPS are more potent diuretics. that's my take on it.
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Old 06-29-2013
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Treatment for nephrogenic diabetes insipidus?

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Pharmacology-, Physiology-, Renal-

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