Biochemistry Flashcards
What is urea
End product of protein metabolism/breakdown in the liver
What are the drawbacks of using urea to measure GFR
Can be affected by protein intake – not constant rate
It is absorbed in the renal tubule
Around 25% returns to the gut - has some extra-renal excretion
Where is creatinine produced
In the muscles
The larger the muscle mass, the more is produced
What is the main way of assessing kidney function
Measure creatinine
What are the drawbacks of using creatine to assess kidney function
Some is secreted in the renal tubule
Affected by age, sex, muscle mass and diet
What is a normal level for GFR
Above 120
What is the relationship between creatinine and GFR
Creatine rises exponentially as the GFR drops
Doesn’t change until GFR is very low though
Which group will have a high creatine (stereotype)
Young men with a large muscle mass
What measurement adjusts the creatinine for age, sex etc
eGFR
What does clearance represent
The volume of plasma that is theoretically cleared of a substance per minute
- includes creatinine cleared in the urine
Why is creatinine clearance a useful measure
sensitive to changes in GFR at the higher levels – picks up changes before creatine rises
How is kidney disease staged
By GFR level
Lower the level, the worse the disease (1-5)
Should protein usually be found in the urine
No - plasma proteins are normally retained
If protein is at >150mg per day you have significant damage
What is malignancy of the plasma cells known as
Multiple myeloma
Produces Ig in an uncontrolled way
Describe nephrotic syndrome
Caused by overflow proteinuria - lose a lot of protein into the urine
This messes up the fluid balance in the body and so fluid moves from capillaries into the interstitial fluid
Leads to oedema - pitting
List ways of expressing/ detecting proteinuria
Dipstick test
Protein:creatinine ratio
Total protein in 24hrs
Albumin:creatinine ratio
What is microalbuminuria
Excretion of albumin in abnormal quantities but still below the limit of protein detection by dipstick
What is microalbuminuria a sign of
Earliest sign of diabetic nephropathy
How do you manage microalbuminuria
Give ACEi to slow progression to full blown nephropathy
List substances that are absorbed in the kidney tubules
Water
Electrolytes
Amino acids
Glucose
Give a pre-renal cause of oliguria (low urine output)
Loss of blood leading to reduced renal perfusion
Give a post-renal cause of oliguria (low urine output)
Stones or malignancy leading to a ureteric/urethral obstruction
Give a renal cause of oliguria (low urine output)
Kidney damage
e.g. glomerulonephritis
If serum and urine osmolality are very similar - what does it mean
Shows the tubules are not absorbing properly
The more similar they are, the worse the condition
