15. Calculation of reabsorption and secretion rate Flashcards Preview

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Flashcards in 15. Calculation of reabsorption and secretion rate Deck (13):
1

Filtered lto eoad - calculation

GFR x plasma concentration

2

excretion rate - calculation

urine flow rate ( ml /min ) x urine concentration

3

renal - how to estimate secretion

Secretion = excreted- filtered

4

renal how to estimate urinary excretion

urinary excretion = glomerular filtration - tubular reabsorption + tubular secretion

5

FENa ?

fractional excretion of sodium

6

fractional excretion of sodium (FENa)

ti is the percentage of the sodium filtered by the kidney which is excreted in the urine

7

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)

8

• What is the formula for filtered load?

Filtered load = glomerular filtration rate × Px ( Px is the plasma concentration of X)

9

• With respect to kidney fluid dynamics, excess filtration compared to excretion leads to ____ (reabsorption/secretion).

Reabsorption

10

• 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

11

• 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).
n

Excretion rate = V × UX = 5 mL/min × 1000 mg/mL = 5000 mg/min

12

• 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)

13

• For Y, a patient's filtered load is 30 mg/min and excretion rate is 20 mg/min. Is Y reabsorbed or secreted?

Reabsorbed (reabsorption rate = filtered - excreted = 30 mg/min - 20 mg/min = 10 mg/min)

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