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Old 02-20-2012
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Kidney Differential Diagnosis of Oliguria!

I am stucked and may be a silly reason but i need help guys.
It says, Differential Dx of Oliguria. and talks about FeNa, Bun:Cr ratio UnA and Uosm.

Pre renal azotema and Acute GN, both have: FeNa less than 1, Bun:cr ratio >15; UNa <20 and UOsm >500

on the other hand

ATN and Post renal azotemia, both have: FeNa more than 2; Bun:Cr ratio < or equal than 15; UNa >40 and UOsm <350

Now, I understand the reasons for fena, bun:cr ratio and una on both sides, both i just cant correlate ATN and post renal azotemia with a UOsm <350. I mean, if there is a damage on the proximal tubular cells (ATN) and and obstruction in post renal; more Na is excreted, due to failure on the tubules cells to reabsob, so why is the reason that the Urine osmolality is less than 350??? shouldnt it be more than 800?
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Old 02-20-2012
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So whats the question in it?
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Old 02-21-2012
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So whats the question in it?
Why is the osmolality <350 in atn and post renal osbtr.?
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Old 02-21-2012
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BUN:Cr is Low in Renal not post-renal
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Old 02-21-2012
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Thank you for pointing that out.
I will clarify and it is post renal but in a prolonged obstruction. < equal 15. (Goljan.)
My doubt is why is it that the UOsm is less than 350?
tnx man!!
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BUN:Cr is Low in Renal not post-renal
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