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Systematic & Cellular Pathology
Renal Pathology
Lecture 2
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Cards (51)
What is one way to assess renal function?
Investigate changes in
filtration rate
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How is glomerular filtration rate (GFR) measured?
By assessing the
clearance of substances
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What is the imaginary substance used to explain
GFR
?
W
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What happens to substance W in the kidneys?
It is freely
filtered
and not
reabsorbed
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If 720mg of W appears in urine over 24 hours, how much was filtered?
720mg
of W was filtered
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What is the concentration of W in the plasma if it is 4mg/litre?
4mg/litre
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How much plasma contains 720mg of W at 4mg/litre concentration?
180
litres of plasma
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How is GFR calculated using inulin?
By measuring its
appearance
in urine
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What is the calculated GFR if 180 litres of plasma is filtered in 24 hours?
125
ml/min
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What substance is used to measure GFR in practice?
Inulin
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What is the first step to find the rate of absorption of phosphate?
Measure GFR using the
inulin technique
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What is the plasma concentration of phosphate if it is
1
mmol/litre?
1 mmol/litre
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How much phosphate is filtered per day at a GFR of 165 litres/day?
165
mmols
of phosphate
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If 40 mmols of phosphate are found in urine, how much is reabsorbed?
125
mmols of phosphate
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What does it indicate if the amount of substance excreted is greater than the amount filtered?
Secretion
must have occurred
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What is renal clearance?
Volume of
plasma
cleared of a substance
Measured per unit time
Indicates
kidney function
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What is the clearance of inulin if it equals GFR?
180 litres
per day
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How is the clearance of phosphate defined?
Volume of
plasma
losing
40 mmol
per day
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What is the formula to calculate clearance of a substance?
C
X
=
C_X =
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=
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X
\frac{mass \ of \ X \ excreted}{plasma \ concentration \ of \ X}
pl
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X
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x
cre
t
e
d
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What does it mean if clearance is less than C_IN?
Substance has been absorbed in
tubules
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What is creatinine clearance useful for?
It approximates
GFR
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What is creatinine a by-product of?
Muscle
metabolism
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How is plasma creatinine used in assessing GFR?
Increased plasma creatinine indicates
reduced
GFR
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What is the normal plasma creatinine concentration?
10 mg/litre
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What happens to creatinine excretion if GFR is reduced?
Creatinine
excretion
will
decrease
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What does an increase in plasma creatinine indicate?
Possible reduction in
renal function
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What is one way to assess renal function?
Investigate changes in
filtration rate
View source
How is glomerular filtration rate (GFR) measured?
By assessing the
clearance
of substances
View source
What is substance W in the context of renal clearance?
An imaginary substance freely
filtered
View source
How does substance W appear in urine?
By
filtration
alone, not
reabsorption
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If 720 mg of W appears in urine over 24 hours, how much was filtered?
720
mg of W was filtered
View source
What is the concentration of W in plasma if it is 4 mg/litre?
4
mg/litre of W in plasma
View source
How much plasma contains 720 mg of W at 4 mg/litre concentration?
180
litres
of plasma
View source
What is the calculated GFR if 180 litres of plasma is filtered in 24 hours?
180 litres/day
or
125 ml/min
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What substance is used to measure GFR in practice?
Inulin
, a freely filtered
polysaccharide
View source
How is GFR calculated using inulin?
By measuring
inulin's
appearance
in
urine
View source
What is the first step to find the rate of absorption of phosphate?
Measure
GFR
using the
inulin technique
View source
What is the plasma concentration of phosphate (PO4-3) in the example?
1
mmol/litre
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If GFR is 165 litres/day, how much PO4-3 is filtered per day?
165
mmols
of PO4-3
View source
What happens if 40 mmols of PO4-3 are found in urine?
125
mmols
of PO4-3 are reabsorbed
View source
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