Renal and Urine Clearance

Question 1

What is the normal filtration rate? normal range?

Answer 1

GFR 125 ml/min; 100-125 ml/min – 160-190 L/day; 180 L/day

Question 2

What is in our filtrate? What’s not filtered List them.

Answer 2

Anything freely filtered
glucose
amino acids
NO filtered- 
Cells
Proteins

Question 3

Equation for Excretion.

Answer 3

E=F-R+S

Question 4

What is filtered load?

Answer 4

FL= GFR x {Plasma]x

Question 5

What is the excretion rate?

Answer 5

E= Ux x V

where.. Ux= urine concentration of a substance
V= flow rate of urine

Question 6

What is clearance?

Answer 6

The volume of plasma that is cleared of substance by the kidneys per unit time.

Question 7

How do you calculate clearance?

Answer 7

C= Ux x Vx/ Px

Question 8

How are GFR and NFP related?

Answer 8

GFR= NFP x Kf 
kf= constant- surface area of nephrons/ amount of nephrons

Question 9

Clearance > GFR…?

Answer 9

Filter and Secrete.

No reabsorption

Question 10

Clearance = GFR…?

Answer 10

ONLY Filter

- USE Inulin to calculate GFR

Question 11

Clearance < GFR…?

Answer 11

Filter and Reabsorb.

No Secretion

Question 12

What is the best way to measure GFR? is it the only way?

Answer 12

1. INULIN- requires many steps- but most accurate way
2. 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

Question 13

What is creatinine?

Answer 13

It comes from the breakdown of muscle (muscle metabolism)

- Creatinine levels do not really change

Question 14

What is the relationship between GFR and plasma creatinine levels?

Answer 14

A decrease in GFR % can cause an increase in Plasma creatinine levels

GFR= 1/Plasma creatinine

Question 15

What is a quick test to check for creatinine levels?

Answer 15

GFR= 1/Plasma creatinine

Question 16

Normal Creatinine levels?

Answer 16

1 mg/dl AKA 1mg/100ml

Question 17

What is the mass principle for what comes in and out of the kidney?

Answer 17

Artery= Vein + Ureters
Kidney(in)= Kidney (out)

Question 18

What is PAH? Why is it important?

Answer 18

1. 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

Question 19

What enters the Renal artery exits where?

Answer 19

The Ureters (all secreted, and therefore excreted!)

Question 20

How do we calculate RPF?

Answer 20

RPF= Clearance of PAH
- because PAH is HIGHLY secreted
RFP= U(PAH)/ P(PAH) x V

Question 21

What is a normal RPF?

Answer 21

600 ml/min

Question 22

What does Clearance of Inulin tell us?

Answer 22

GFR

Question 23

What does Clearance PAH tell us?

Answer 23

RPF

Question 24

2 ways to calculate GFR?

Answer 24

1. Clearance of inulin

2. Clearance of Creatinine

Question 25

How do you calculate filtration fraction? What is it?

Answer 25

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

Question 26

How do you calculate RBF?

Answer 26

RBF= RPF/ 1- hematocrit