Practical 5: Use of Serum Tests to Detect Renal Dysfunction Flashcards
What are the two most common tests ordered to detect renal dysfunction?
Serum creatinine
Serum urea
What is urea the product of
AN end product of protein metabolism
When might high urea be seen?
(4)
High protein diet
Excessive tissue breakdown
In the presence of GI bleeding
Dehydration
What is the role of the kidneys in relation to urea
(3)
Kidneys regulate urea livers
Urea is filtered in the glomeruli and reabsorbed in the tubules
Excretion of urea decreases when GFR drops
Why does a drop in GFR result in a decrease in urea excretion
The longer the tubular fluid remains in the kidney the greater the reabsorption of urea into the blood
What is creatinine
A product of creatine metabolism in muscle
What do blood values of creatinine depend on?
Blood concentration of creatinine depends closely on GFR
What is normal creatinine level proportional too
Proportional to muscle mass
What does it mean if creatinine value has doubled
GFR and renal function has probably fallen to half
Is serum urea or serum creatinine a more specific indicator of GFR
Serum creatinine is more specific
-> serum urea concentrations may vary independently of the GFR but a rise in serum creatinine almost always represents a reduction in GFR
When might you see low urea laevel
Not eating properly or not able to keep food down
When might you see high urea levels
(4)
Unusually high protein intake
GI bleed
Infection
Inadequate dialysis
What may indicate an inadequate dialysis
Lack of appetite for protein-containing foods or nausea when eating them
What might cause an elevation of urea
Increased metabolism -> can be the result of fever
Some drugs that affect metabolism (creatinine might also be affected)
What might cause a decrease in urea/creatinine
Muscle loss (could be from not eating)
