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  #1  
Old 03-19-2012
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Kidney Calculating renal reabsorption!

A 35-year-old man with a history of recurrent urinary tract infections comes to the physician because of pain during urination. He is diagnosed and treated for a urinary tract infection. Because of his history, further investigation is warranted. The following data are obtained from the patient:
Inulin clearance

100 mL/min
Plasma osmolarity
286 mOsm/L
Plasma sodium concentration
140 mEq/L
Urine flow
1.44 L / 24 hour
Urine osmolarity
205 mOsm/L
Urine sodium concentration

100 mEq/L

How much sodium does this patient reabsorb each day?
:sorry::sorry:

[A] 14 mEq
[B] 144 mEq
[C] 244 mEq
[D] 20,016 mEq
[E] 20,160 mEq
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  #2  
Old 03-19-2012
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if you can tell me wtf a mEq is (something I've never understood) then I can do this question.

1 mEq = how many mOsm?

because once you have that its just

reabsorption = Filtered load - excretion rate = (GFR x [plasma sodium]) - (urine flow rate x [urine sodium])
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Old 03-19-2012
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how do you get the GFR?
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Old 03-19-2012
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Quote:
Originally Posted by MedPharm View Post
how do you get the GFR?
GFR = INULINE clearance

and guys forget about osmolalilty .. we dont need it .. its all about unit conversion witch i haven't practice yet
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Quote:
Originally Posted by MedPharm View Post
how do you get the GFR?
i assume we use 100 or 120 here (since we dont have inulin or creatinine info).
id try both and see which of the answers i get is on the list of options lol
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if all sucks -> use gut-feeling...i'd go with D and move on
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Quote:
Originally Posted by MedPharm View Post
if all sucks -> use gut-feeling...i'd go with D and move on
my gut feeling is E lol
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Old 03-19-2012
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my gut feeling says: dude, you calculated something (that didn't work out) and ended up with XXXX-144 so...last digit is 6 -> wish you good luck with that

me: ok, gut-feeling. as i have no better idea
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Old 03-19-2012
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Default ans. D. 20,016 mEq

ans. D. 20,016 mEq

Reabsorption= Filtration - Excretion = (GFR x P) - (U x V)

GFR=100ml/min; P=140mEq/L

U=100mEq/L

V=1.44L/24h

Filtration=GFR x P

=100ml/min x 140mEq/1000ml

=14mEq/min

=14mEq x 1440/24h

= 20160mEq/24h

Excretion=U x V

=100mEq/L x 1.44L/24h

=144mEq/24h

Reabsorption= (20160-144)mEq/24h = 20016mEq/24h
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my gut-feeling in a mathematical genus
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Default

great problem
just dont look at osmolality
gfr=inulin clearance=100*140
but look at the units
its in ml,min
so convert it
GFR=(100*140*60*24)/1000 and unit is meq/Day
now excretion is(1.44*100)=144meq/day
absorbed=filtered -excreted=20016meq
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Old 03-21-2012
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Default help!

guys, im really confused

as i see it, it is:

reabsorption = (V x Ux) - (GFR x Px)
=(140x144) - (100x286)
=28700 - 28600
=100

im way off, where am i going wrong :/
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Old 03-21-2012
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this is a question from kaplan q bank
a typic wtf type questions...i kept scratching my head
while doing this for 5 min i tried and then gave up and got the next few questions also wrong as i ran out of time
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Old 03-22-2012
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Quote:
Originally Posted by Dr.NickRiviera View Post
guys, im really confused

as i see it, it is:

reabsorption = (V x Ux) - (GFR x Px)
=(140x144) - (100x286)
=28700 - 28600
=100

im way off, where am i going wrong :/

reabsorption = (GFR x Px) - (V x Ux)


GFR= 100 mL/min= 144 l / 24 h
Px = 140 mEq/L

GFR X Px = 144 x 140 = 20160


V = 1.44 l/ 24 h
Ux = 100 mEq/l

V x Ux = 144 mEq

20160 - 144 = 20,016 mEq
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The answer is A


GFR= 100ML/min (convert this to L = 0.1L/min)
V= 1.44L/24 hours (convert this to per min = 1.44/1440mins = 0.001)

resorption= filtered - excretion
resorption = (GFR x Px) - (V x Ux)

resorption= (0.1 x 140) - (0.001 x100)
=13.9 or 14.
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Old 3 Weeks Ago
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Default Answer for renal absorption

Answer is D. Just subtracting the amount excreted from the filtered load.
Amt absorbed = Filtered load - Amt excreted
= GFR x Plasma concn - Urinne flow rate x Urine concn
(GFR= 100ml/min = 100x1440 /1000 =144 L/day)

Amt absorbed = 144L/dayx140meq/l - 1.44L/dayx100meq/l
= 20016 meq/day
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