Biochemical measurements in renal disease Flashcards
What tests are used to measure glomerular function (GFR)?
Urea
Creatinine
eGFR
What is urea?
End breakdown product of protein from the colon and liver
What is creatinine?
Product of protein intake - it will change depending on the muscle mass of a person and the protein intake of a person
What is a normal GFR?
Around 120 ml/min - anything above is normal
What is the issue with creatinine as a measurement of GFR?
Between 60-120, the creatinine won’t really change
What is the issue with urea as a measurement of GFR?
Dependent on the protein content in the diet
Reabsorbed from the renal tubule
Around 25% is eliminated in the liver
What are confounders to serum creatinine?
Age Sex Ethnicity Muscle mass Diet
What is eGFR?
Adjusts for proxies of diet, muscle mass, age, sex and ethnicity
How is urinary creatinine clearance calculated?
creatinine in the urine x urine volume
DIVIDED BY
creatinine in the serum x duration of collection
What is the best way to determine a precise GFR?
Cr-EDTA clearance - not used that often
What GFR indicated kidney damage?
GFR 60-90
What GFR indicated moderate kidney damage?
30-59
What GFR indicated severe kidney damage?
15-29
What GFR indicates kidney failure?
Less than 15
How is proteinuria measured?
24-hour collection
Protein/creatinine ratio of a spot sample is also helpful
What level of proteinuria indicated significant glomerular damage?
More than 150mg/day
What are the different types of proteinuria?
Normal Overflow (multiple myeloma) Glomerular (albuminuria) Tubular Secreted
What is nephrotic syndrome?
Loss of albumin in the capillaries creating a low oncotic pressure, therefore the fluid will leak out of the capillaries into the surrounding tissues (pitting oedema, periorbital swelling)
What is microalbuminuria?
Excretion of albumin in abnormal quantities by still below the limit of protein detection by dipstick
What is the treatment for microalbuminuria?
ACEI
What can cause an intrinsic kidney tissue damage?
Glomerulonephritis
Pyelonephritis
What can cause reduced renal perfusion?
Hypovolaemia
What can cause a post-renal damage?
Stones or malignancy
What will pre-renal failure show biochemically?
Tubules working
Urine sodium <20 mmol/L
Urine/serum urea >10:1
Urine/serum osmolality >1.5:1
What will intrinsic renal damage show biochemically?
Tubules NOT working
Urine sodium >40mmol/L
Urine/serum urea <3:1
Urine/serum osmolality <1/1:1
