Renal and Urine Clearance Flashcards
What is the normal filtration rate? normal range?
GFR 125 ml/min; 100-125 ml/min – 160-190 L/day; 180 L/day
What is in our filtrate? What’s not filtered List them.
Anything freely filtered glucose amino acids NO filtered- Cells Proteins
Equation for Excretion.
E=F-R+S
What is filtered load?
FL= GFR x {Plasma]x
What is the excretion rate?
E= Ux x V
where.. Ux= urine concentration of a substance
V= flow rate of urine
What is clearance?
The volume of plasma that is cleared of substance by the kidneys per unit time.
How do you calculate clearance?
C= Ux x Vx/ Px
How are GFR and NFP related?
GFR= NFP x Kf kf= constant- surface area of nephrons/ amount of nephrons
Clearance > GFR…?
Filter and Secrete.
No reabsorption
Clearance = GFR…?
ONLY Filter
- USE Inulin to calculate GFR
Clearance < GFR…?
Filter and Reabsorb.
No Secretion
What is the best way to measure GFR? is it the only way?
- INULIN- requires many steps- but most accurate way
- NO- we can also use Creatinine- BUT it is a little of an overestimation- and a small portion is actually secreted- but it is easier to calculate
What is creatinine?
It comes from the breakdown of muscle (muscle metabolism)
- Creatinine levels do not really change
What is the relationship between GFR and plasma creatinine levels?
A decrease in GFR % can cause an increase in Plasma creatinine levels
GFR= 1/Plasma creatinine
What is a quick test to check for creatinine levels?
GFR= 1/Plasma creatinine
Normal Creatinine levels?
1 mg/dl AKA 1mg/100ml
What is the mass principle for what comes in and out of the kidney?
Artery= Vein + Ureters Kidney(in)= Kidney (out)
What is PAH? Why is it important?
- ParaAminoHipuric Acid - is NOT endogenous, but it is ONLY filtered and SECRETED.
It is so highly secreted that it enters the renal artery- and will be
a. excreted ONLY in urine
b. NO PAH will come out of the vein
What enters the Renal artery exits where?
The Ureters (all secreted, and therefore excreted!)
How do we calculate RPF?
RPF= Clearance of PAH
- because PAH is HIGHLY secreted
RFP= U(PAH)/ P(PAH) x V
What is a normal RPF?
600 ml/min
What does Clearance of Inulin tell us?
GFR
What does Clearance PAH tell us?
RPF
2 ways to calculate GFR?
- Clearance of inulin
2. Clearance of Creatinine
How do you calculate filtration fraction? What is it?
FF= GFR/ RPF
It is a ratio of GFR and RPF- it tells us how much of what enters the kidney will actually be filtered
AKA a ratio of what is filtered/ total blood flow
How do you calculate RBF?
RBF= RPF/ 1- hematocrit
