Flashcards in 11. Glomerular filtration rate Deck (13):
glomerular filtration rate ( GFR) estimates
how much blood passes through the glomeruli each minute
GFR = inulin clearance = (Urine concentration of inuline x urine flow rate ) / plasma concentration of inulin = Starling equation
Normal GFR -=
100 ml / min
Starling equation GFR
GFR = Kf ( ( Pgc - Pbs ) - ( π gc - πbs))
gc : glomerular capillary
bs : bowman space
Kf : filtration constant
πbs = 0
creatine clearance - clinical relevance
it is an aprroximate measure of GFR -- > slighlty overestimates GFR because creatinine is moderaterly secreted by rena tubules
chronic kidney disease - GFR measure
incremental reductions in GFR define the stafesof chronic kidney disease
creatinine serume concentration
0.6 -1.2 mg/ dl or 53-106 μmol/L
• What is the unit of measurement for the glomerular filtration rate (GFR)?
Volume over time; usually measured in milliliters per minute (mL/min), similar to clearance
• Exogenous ____ (inulin/creatinine) or endogenous ____ (inulin/creatinine) is used to calculate GFR, which is normally about ____ mL/min.
Inulin (freely filtered, neither reabsorbed nor secreted); creatinine (yields slight overestimate, is secreted in tubules); 100 mL/min
• Inulin is infused into a patient to assess renal function. What can it be used to measure, and how?
Inulin clearance (GFR = urine inulin concentration times urine flow rate divided by plasma inulin concentration [Uinulin × V/Pinulin])
• Creatinine clearance ____ (overestimates/underestimates) glomerular filtration rate as creatinine is ____ (secreted/reabsorbed) by tubules.
Overestimates; secreted (the plasma concentration of creatinine is slightly lower than it would be from filtration alone)
• Which formula calculates the glomerular filtration rate (GFR) by relating the glomerular capillary (GC) and Bowman space (BS) pressures?
GFR = Kf [(PGC - PBS) - (ΠGC - ΠBS)], where Kf = filtration constant; P = hydrostatic pressure difference; Π = oncotic pressure difference