Urea absorption in the kidney

[anbuitachi]

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Hi can someone give me a short summary of what happens to urea after it goes into the glomerulus and into the tubules.. I couldn't find a good source on google.. [pretty much where it is absorbed.. or excreted.. and around how much]. Thank you!

 

[Oreoomar]

I think it is reabsorbed in the proximal tubule and the rest is dependent on ADH. More ADH allows water and urea to be reabsorbed in the cortical ducts. The rest is excreted. That should be all you need to know about it - theres a graph showing the urea concentration that is reabsorbed in the proximal tubule compared to water in First Aid in the renal physiology section as well.

 

[g8orlife]

I think it is reabsorbed in the proximal tubule and the rest is dependent on ADH. More ADH allows water and urea to be reabsorbed in the cortical ducts. The rest is excreted. That should be all you need to know about it - theres a graph showing the urea concentration that is reabsorbed in the proximal tubule compared to water in First Aid in the renal physiology section as well.

To add to this, urea follows water. So whenever water is reabsorbed, imagine urea being reabsorbed too.

 

[anbuitachi]

Oh thanks!!!

 

[hsk013]

I had this question on Rx.

Excessive fluid intake in a patient who has participated in a marathon would result in hyponatremia and therefore decrease reabsorption of urea from the medullary collecting duct.

If urea follows water, wouldn't excessive fluid intake lead to increased reabsorption in urea? (along with hyponatermia since you now have more water in your blood).

Or does more urea get absorbed in PCT that less is reabsorbed at the medullary collecting duct? Can someone explain this for me?

 

[Rahas]

50% of filtered urea gets reabsorbed in the PCT. This reabsorption is linked to Na.

The amount of filtered urea that is eventually excreted depends on ADH levels. ADH increases urea reabsorption, so it decreases urea clearance.

For the marathon patient, I'm guessing he dehydrated and replaced the sweat lost with pure water. This decreases serum osmolality -> decreases ADH secretion -> decreases urea reabsorption.

 

[Rihan]

Excess fluid intake AFTER a marathon would inhibit ADH activity and therefore decrease water + urea reabsorption