Renal clearance

Question 1

Clearance

Answer 1

C=U*V/P in mL/min

U=urine concentration
V=urine volume flow rate
P=plasma concentration

Question 2

If C<GFR

Answer 2

net tubular reabsorption of X

Question 3

If C>GFR

Answer 3

Net tubular secretion of X (like creatinine)

Question 4

IF C=GFR

Answer 4

no net secretion or reabsorption

Question 5

GFR

Answer 5

GFR=Uinulin x V/ P inulin= C inulin
GFR=Kf[(Pgc-Pbc)-(PIgc- PIbc)]

gc=glomerular capilary
bs=Bowman’s capsule
PIbs= normally equal zero

Question 6

Normal GFR

Answer 6

100mL/min

Question 7

Creatinine

Answer 7

An approximate measure of GFR

Slightly overestimates GFR because moderately secreted by the renal tubules

Question 8

Effective renal plasma flow

Answer 8

ERPF: estimated using PAH clerance as it is both filtered and actively secreted in the proximal tubule

All PAH entering the kidney is excreted

ERPF = Upah * V/ P pah

Question 9

Renal blood flow

Answer 9

RBF = RPF /(1 - Hct)

Question 10

ERPF ~ RPF

Answer 10

ERPF underestimates true RPF by 10%

Question 11

Filtration

Answer 11

Filtration fraction FF = GFR/RPF

Question 12

Normal filtration fraction

Answer 12

Normal FF = 20%

Question 13

Filtered load

Answer 13

Filtered load = GFR x plasma concentration

Question 14

GFR estimate

Answer 14

GFR estimated with creatinine

Question 15

RPF estimate

Answer 15

PAH clearance