11. Glomerular filtration rate

Question 1

glomerular filtration rate ( GFR) estimates

Answer 1

how much blood passes through the glomeruli each minute

Question 2

GFR calculation

Answer 2

GFR = inulin clearance = (Urine concentration of inuline x urine flow rate ) / plasma concentration of inulin = Starling equation

Question 3

Normal GFR -=

Answer 3

100 ml / min

Question 4

Starling equation GFR

Answer 4

GFR = Kf ( ( Pgc - Pbs ) - ( π gc - πbs)) 
gc : glomerular capillary
bs : bowman space
Kf : filtration constant
πbs = 0

Question 5

creatine clearance - clinical relevance

Answer 5

it is an aprroximate measure of GFR – > slighlty overestimates GFR because creatinine is moderaterly secreted by rena tubules

Question 6

chronic kidney disease - GFR measure

Answer 6

incremental reductions in GFR define the stafesof chronic kidney disease

Question 7

creatinine serume concentration

Answer 7

0.6 -1.2 mg/ dl or 53-106 μmol/L

Question 8

• What is the unit of measurement for the glomerular filtration rate (GFR)?

Answer 8

Volume over time; usually measured in milliliters per minute (mL/min), similar to clearance

Question 9

• Exogenous ____ (inulin/creatinine) or endogenous ____ (inulin/creatinine) is used to calculate GFR, which is normally about ____ mL/min.

Answer 9

Inulin (freely filtered, neither reabsorbed nor secreted); creatinine (yields slight overestimate, is secreted in tubules); 100 mL/min

Question 10

• Inulin is infused into a patient to assess renal function. What can it be used to measure, and how?

Answer 10

Inulin clearance (GFR = urine inulin concentration times urine flow rate divided by plasma inulin concentration [Uinulin × V/Pinulin])

Question 11

• Creatinine clearance ____ (overestimates/underestimates) glomerular filtration rate as creatinine is ____ (secreted/reabsorbed) by tubules.

Answer 11

Overestimates; secreted (the plasma concentration of creatinine is slightly lower than it would be from filtration alone)

Question 12

• Which formula calculates the glomerular filtration rate (GFR) by relating the glomerular capillary (GC) and Bowman space (BS) pressures?

Answer 12

GFR = Kf [(PGC - PBS) - (ΠGC - ΠBS)], where Kf = filtration constant; P = hydrostatic pressure difference; Π = oncotic pressure difference

Question 13

• Incremental ____ (reductions/elevations) in GFR define the stages of chronic kidney disease.

Answer 13

Reductions