GFR and ERPF

Question 1

extraction ratio (ER)

Answer 1

fraction of substance removed from plasma during one circulation through kidney

Question 2

extraction ratio measures …

Answer 2

urine elimination and renal retention

Question 3

what does a ER of 1.0 mean?

Answer 3

1) that the drug is completely removed from circulation in a single pass
= true measurement of RPF
2) or drug is completely retained = ideal for morphology

Question 4

what RP is best used for ERPF?

Answer 4

MAG3

Question 5

formula for ER

Answer 5

ER = (arterial concentration of substance - venous concentration of substance)/arterial concentration of substance

Question 6

which RP is best for morphology?

Answer 6

DMSA

Question 7

renal clearance

Answer 7

amount of substance that appears in the urine in a given time

Question 8

formula for renal clearance

Answer 8

renal clearance (ml/time) = ([urine] * vol/min)/[plasma]

Question 9

which RP is completely filtered by the glomerulus, therefore is good to measure GFR?

Answer 9

DTPA

Question 10

indications

Answer 10

• monitoring function in renal disease
• monitor renal function throughout course of nephrotoxic drug admin
• eval renal function in live tx donors
• follow up post tx

Question 11

camera GFR technique
Gate’s Method

Answer 11

• pre-injection counts of syringe on camera
• dynamic imaging for min 6 mins
• post-injection syringe counts

Question 12

blood sample technique

Answer 12

• single/serial blood sample techniques
• determine time
• compare to standard

Question 13

Dose required for Gate’s Method

Answer 13

111 MBq

Question 14

distance the syringe is at for gate’s method

Answer 14

syringe counted 20-30 cm from face of camera

Question 15

dose for GFR blood sampling technique

Answer 15

370-555 MBq

Question 16

theory for gfr blood sampling

Answer 16

% of tracer remaining in blood at specific times indicate renal functions – clearance and filtering through kidneys (tracer excreted by kidneys)

Question 17

high plasma counts = GFR ______

Answer 17

low

Question 18

low plasma counts = GFR ______

Answer 18

high

Question 19

four broad stages for GFR measurements

Answer 19

1. tracer prep
2. tracer admin
3. blood sampling
4. sample counting

Question 20

if you draw from the same arm as the injection, what will happen to your GFR?

Answer 20

it’ll make the GFR look lower because your counts might be higher

Question 21

if you collect the blood sample 30 mins too early, what happens?

Answer 21

plasma counts will be too high = gfr look lower

Question 22

if you collect the blood sample 30 mins too late, what happens?

Answer 22

plasma counts will be too low = gfr look higher

Question 23

renal plasma flow

Answer 23

amount of plasma at the glomerulus

Question 24

formula for effective renal plasma flow

Answer 24

C = U x V/P

Question 25

RP for ERPF

Answer 25

MAG3

Question 26

RP for GFR

Answer 26

DTPA

Question 27

RP for morphology

Answer 27

DMSA

Question 28

Which of the following are appropriate times for acquiring plasma samples in a multi- sample GFR study?

a. Immediately, 1hr and 3hrs
b. 30 min, 1hr and 2hrs
c. 2hr, 3hrs, and 4hrs
d. 3hrs, 4hrs and 24hrs

Answer 28

c - need at least 1 hr for equilibrium