Flashcards in 12. Effective renal plasma flow Deck (13):
Effective renal plasma flow ( eRPF) is ised to
calculate plasma flow (RPF) and hence estimate renal function
Effective renal plasma flow (eRPF) can be estimating using ... (why)
para- aminohippurinc ( PAH) clearance because filtration and secretion is nearly 100% excretion of all PAH that enter kidney
Effective renal plasma flow ( eRPF) calculation
para- aminohippurinv ( PAH ) clearance = Upah x V/ Ppah
renal blood flow (RBF) is the
volume of blood delivered to the kidneys per unit time
renal blood flow (RBF) - calculation
renal blood flow (RBF) = RPF / (1-Hct)
eRPG vs true renal plasma flow
eRPF underestimates true renal plasma flow slightly
• What substance's clearance is used to estimate renal plasma flow? Why?
Para-aminohippurate (PAH); 100% of PAH is actively secreted from the proximal tubule into the urine (the renal vein PAH concentration is 0)
• What is the formula for estimating the effective renal plasma flow (ERPF) using para-aminohippuric acid (PAH)?
ERPF = urine PAH concentration times the urine flow rate divided by the plasma PAH concentration (UPAH × V/PPAH)
• What is the formula for estimating renal blood flow (RBF) if renal plasma flow (RPF) is known?
RBF = RPF divided by (1 - the hematocrit) (normally, RBF is double the RPF)
• You infuse para-aminohippuric acid (PAH) into a patient. An hour later, you still detect a trace of PAH in the patient's blood. Why?
Ten percent of renal blood flow goes to the kidney parenchyma rather than through the glomerulus; PAH in this blood is not filtered
• Effective renal plasma flow ____ (overestimates/underestimates) true renal plasma flow by approximately ____%.
Underestimates; 10 (because 10% of renal blood flow supplies the kidney parenchyma rather than passing through the glomerulus)
• A man gets PAH. Plasma level (PPAH) is 2 mg/mL, urine level (UPAH) 550 mg/mL, urine flow (V) 4 mL/min. What is his ERPF (mL/min)?
ERPF = CPAH (mL/min) = (UPAH × V)/PPAH = (550 × 4)/2= 1100 mL/min