Clearance Flashcards
(37 cards)
Define Clearance.
“The volume of blood or plasma that can be freed of a specified constituent in a specified time (usually one minute)
How are the stages chronic kidney disease determined?
Chronic kidney disease is staged on the basis of GFR as estimated by creatinine (GFR proportional to 1/SCr)
What is the definition (clinical measurement) of chronic kidney disease?
Chronic kidney disease = kidney damage or GFR < 60 mL/min/1.73 m for >/= 3 months
How is kidney damage defined?
Kidney damage is defined as pathologic abnormalities or markers of damage, inc. abnormalities in blood or urine tests or imaging studies.
What is the equation for renal clearance?
Cx= (Ux/Px) x V
What happens to inSulin in the kidney?
InSulin is freely filtered, reabsorbed in proximal tubule taken up by endocytosis and degraded to constituent AA –> very little in final urine
What happens to inulin in the kidney?
Inulin is freely filtered; not reabsorbed, secreted or metabolized –> all filtered ends up in the final urine
How do the renal clearance of Insulin and inulin compare?
C inS < C in
Under what circumstances would maximum renal clearance occur?
Filtratio alone is not enough, reabsorption will lower clearance
to maximize the clearance –> secrete everything else into the tubule, filtration is only a subset of what goes thru the glomerulus
What are the units for clearance?
“VOLUME per time” ex: mL/min, mL/min/kg or m2
What term is used to describe: “the amount of blood or plasma that has been “completely cleaned” of a substance.
“Clearance”
What term is used to describe: “the amount of substance filtered into Bowman’s space per unit time”
“Filtered load”
Define Clearance.
The amount of blood or plasma that has been completely cleaned of a substance
Define “Filtered load”
The amount of substance filtered into Bowmans space per unit time (an amount not a volume)
Filtered load is measured as: A. Weight B. Weight per unit time C. Volume D. Volume per unit time E. Weight per unit volume
B. Weight per unit time
What term is used to describe: “the amount of substance filtered into Bowman’s space per unit time”
“Filtered load”
Define Clearance.
The amount of blood or plasma that has been completely cleaned of a substance
Define “Filtered load”
The amount of substance filtered into Bowmans space per unit time (an amount not a volume)
Filtered load is measured as: A. Weight B. Weight per unit time C. Volume D. Volume per unit time E. Weight per unit volume
B. Weight per unit time
Clearance of “x” only measures GFR if…..?
“X” enters only as filtrate and exits only in final urine.
Can we measure GFR using Clearance measurements?
Yes- as long as [X] plasma = [X] in filtrate
must remain in filtrate unchanged until final urine: no reabsorption, no secretion, no degradation while in tubules.
What is the “gold standard” for GFR/Clearance measurements?
Inulin- a polysaccharide, freely filtered,
cant pass through tight jxns, no transport mechanisms, no enzymes present in tubular lumen to degrade.
T/F creatinine is often used as a surrogate for inulin?
True - easier to measure, should be constant
If GRF decreases by 50%, what happens to Serum Creatinine levels?
Serum Creatinine inc. 2x
