Flashcards in 15. Calculation of reabsorption and secretion rate Deck (13):
Filtered lto eoad - calculation
GFR x plasma concentration
excretion rate - calculation
urine flow rate ( ml /min ) x urine concentration
renal - how to estimate secretion
Secretion = excreted- filtered
renal how to estimate urinary excretion
urinary excretion = glomerular filtration - tubular reabsorption + tubular secretion
fractional excretion of sodium
fractional excretion of sodium (FENa)
ti is the percentage of the sodium filtered by the kidney which is excreted in the urine
fractional excretion of sodium (FENa) - calculation
Na+ excreted / Na+ filtered = (urine flow rate x urine concentration of Na+ ) / (GFR x plasma concentration of NA+ ) = ( urine flow rate x urine concentration of Na+ ) / ( Ucr x V /Pcr x plasma concentration of Na+ ) = ( Pcr x UNa) / ( UCRr x P Na)
• What is the formula for filtered load?
Filtered load = glomerular filtration rate × Px ( Px is the plasma concentration of X)
• With respect to kidney fluid dynamics, excess filtration compared to excretion leads to ____ (reabsorption/secretion).
• A patient's GFR is 125 mL/min and plasma concentration of substance X is 20 mg/mL. What is the filtered load of X (mg/min)?
Filtered load = GFR × plasma concentration = 125 mL/min × 20 mg/mL = 2500 mg/min
• A patient's urine flow (V) is 5 mL/min. X is found in his urine at a concentration of 1000 mg/mL (UX). Find the excretion rate (mg/min).
Excretion rate = V × UX = 5 mL/min × 1000 mg/mL = 5000 mg/min
• For X, a patient's filtered load is 100 mg/min and excretion rate 200 mg/min. Is X reabsorbed or secreted?
Secreted (secretion rate = excreted - filtered = 200 mg/min - 100 mg/min = 100 mg/min)