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R3
Clearance
18
Physiology
Professional
02/19/2013

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Cards

Term
what is the definition of renal clearance?
Definition
the volume of plasma per minute from which all of any substance (X) is removed from the blood into the urine
Term
what units does clearance have?
Definition
ml/min (same as flow)
Term
What is the equation for clearance?
Definition
Cx = (Ux x Vdot)/Px
Term
What three tests do you need to calculate the clearance of any substance?
Definition
arterial blood sample, a urine sample, and a urine flow rate
Term
What changes in the F + S = R + E equation for inulin?
Definition
it becomes F = E because inulin is neither secreted nor reabsorbed
Term
What is the clearance of inulin equal to?
Definition
clearance of inulin = GFR
Term
What is GFR comparable to in the lungs?
Definition
FRC
Term
what does it mean if C(X) > C(inulin)?
Definition
the substance X must also be secreted in addition to being filtered
Term
what does it mean if C(X) < C(inulin)?
Definition
the substance X, if filtered, must also be reabsorbed from the tubules
Term
what exogenous organic anion is 90% cleared from the blood on a single pass through the kidneys?
Definition
paraaminohippurate (PAH)
Term
what equations do we use when estimating effective renal plasma flow with PAH?
Definition

ERPF = CPAH = UPAH x Vdot/PPAH

RPF = 1.1 x EPRF

RBF = RPF/(1-HCT)

Term
what endogenous substance is a good substitute for inulin?
Definition
creatinine
Term
how is creatinine produced in the body?
Definition
it is a product of muscle metabolism
Term
how is plasma creatinine a detector of renal failure?
Definition
high levels of plasma creatinine suggest low GFR
Term
what is normal GFR and PCr? how do you calculate the load of creatinine from the two?
Definition

GFR = 180 L/day (125 ml/min)

PCr = 1mg/100mL

GFR x PCr = LoadCr

 

Term
how is urea produced in the body?
Definition
it is a metabolic product of protein catabolism
Term
what is the relationship between BUN and creatinine concentrations in the blood?
Definition
BUN concentrations are normally 10x higher than creatinine
Term
what are urea concentrations a reflection of? what are creatinine concentrations a reflection of? which is less stable?
Definition

[urea] is a reflection of proteins meals [creatinine] is a reflection of body mass

urea is much less stable over time

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