DI ??

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DI ??

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usmleasr
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07/22/04 - 10:12 AM

when urine osmolarity and serun osmolarity is given how do u differentiate between diabetes insipidus and primary polydipsia ??(with these two values alone) :roll:

dimps
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07/22/04 - 10:59 AM

In DI--serum osmolarity is increased ie more than290 mosmoles while urine osmolarity is decreased

in primary polydipsia---serum osmolarity & urine osmolarity both r decreased

Water deprivation test may be needed for correct distinction: Generally, fluids are withheld for a period of time. ADH is then administered. Periodic urine osmolarity measurements are done.
In normal people (and those with primary polydipsia since their pituitary is normal), urine osmolarity doesn't increase more than 9% after ADH .
In central DI, rise in urinary osmolarity is greater than 9% after ADH.
In nephrogenic DI, there is no change in urine osmolarity with either dehydration or with ADH administration.

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usmleasr
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07/22/04 - 11:21 AM

"dimps" wrote:
In DI--serum osmolarity is increased ie more than290 mosmoles while urine osmolarity is decreased

in primary polydipsia---serum osmolarity & urine osmolarity both r decreased 8)

.

..yeah i agree with this point...

usmleasr
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07/22/04 - 11:24 AM

"dimps" wrote:

Water deprivation test may be needed for correct distinction: Generally, fluids are withheld for a period of time. ADH is then administered. Periodic urine osmolarity measurements are done.
In normal people (and those with primary polydipsia since their pituitary is normal), urine osmolarity doesn't increase more than 9% after ADH .
In central DI, rise in urinary osmolarity is greater than 9% after ADH.
In nephrogenic DI, there is no change in urine osmolarity with either dehydration or with ADH administration.

. :roll:

this point i am a bit confused.. :? ..water deprivation test , i guess depriving fluids increases both urine and serum in primary polydipsia...
but not in DI...
and ADH test is done seperately to decide if, DI is central or nephrogenic..
correct me if i am wrong

dimps
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Topics: 63
Posts: 446

07/22/04 - 11:40 AM

ya this is true that water deprivation increases urine and serum osmolarity in primary polidipsia
not in DI

but often it is continued by giving ADH to distinguish between central & nephrogenic DI

u can check this site
http://www.emedicine.com/ped/topic580.htm

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usmleasr
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07/22/04 - 12:38 PM

thanks

asmi
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07/22/04 - 12:46 PM

Hi dimps and usmleasr,

Even i get confused in here,

So water deprivation test....inc urine and serum osmolality in primary polydipsia and no change in DI .

Then you go for injecting ADH....in CDI..urine osmolality increases,while in NDI and primary polydipsia it doesnot .What about serum osmolality in all ?

Am i getting it right friends :?:

thanks

usmleasr
Forum Guru

Topics: 105
Posts: 970

07/22/04 - 01:36 PM

hi asma,

water deprivation test is to ans the q ....primary polydipsia or DI??

ADH inj is to ans the q central DI or nephrogenic DI??

in water deprivation as u said , in primary polydipsia both serum and urine osm inc...
no change with DI..

in ADH test ,( remember in DI serum osm is normal to high already)...we concentrate on urine osm to diff central and nephrogenic cause..
if urine osm inc means central
no change means nephrogenic

asmi
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Topics: 1043
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07/22/04 - 02:08 PM

Thanks usmleasr smiling face

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