Kidney and Renal function Flashcards
Name 3 nitrogenous wastes
Urea, creatinine and uric acid
Functions of renal system
Endocrine, metabolic, homeostatic, excretory
What happens blood volume when there is many salts in the body
blood volume increases
How many litres are filtered by kidneys per day
180L
What molecular weight is forced out of glomerulus
<68,000
What happens in the DCT
Exchange of Na+ for K+ under aldosterone control
What happens in loop of henle
Descending H2O is lost, ascending Na+ is lost
What is the average GFR
125ml/min
What is GFR influenced by
Filtration pressure and filtration coefficient
What hormones are synthesised by the kidney
Renin and erythropoietin
Function of aldosterone
Regulate sodium and potassium levels and increase water retention
Function of antidiuretic hormone
Water absorption in collecting ducts
What does pre renal refer to
Any condition that results in reduced blood flow to the kidneys
What does renal refer to
Damage to renal tissue, glomerular basement membrane/tubules
What does post renal refer to
Obstruction to urine outflow
Reference range for serum urea
1.7-8.3mmol/L
How does urea end up in the blood
End product of protein and amino acid catabolism
Suitable samples for serum urea testing
Serum, plasma, urine, amniotic fluid, other bodily fluids. Deprotinised whole blood
Why is refrigeration of urea necessary
Urea can be destroyed by bacteria
Principle of urea assay
Measure nitrogen content of urea and not urea directly
Enzyme used in urea hydrolysis
Urease
What is nesselers reagent
Iodine salt of mercury and potassium
What occurs in nesseleres reaction
Nesselers reagent is reacted with the amonia formed in the urease reaction. Forms brown colour which can be measured enzymatically
Name the catalyst in the berthelot reaction
sodium nitroprusside
What occurs in the berthelot reaction
Amonia formed in urease reaction reacts with phenol and sodium hypochlorite to form blue indophenol.
Name 2 enzymes used in kinetic method
Urease and glutamate dehydrogenase
Pre renal causes for increased urea
low blood pressure, decreased blood flow, increased dietary protein
Renal causes for increased urea
renal disease with decreased glomerular filreation. Glomerular nephritis, renal failure from diabetes
Post renal causes for decreased urea
UTI’s, kidney stones, bladder tumour
Pre renal causes for decreased urea
liver disease, high fluid intake, decreased dietary protein, increased protein synthesis.
Where is creatine formed
Liver and pancreas
What is creainine
A waste product of creatine formed during normal muscle metabolism
Reference range for creatinine serum
Men 62-115umol/L Women 53-97 umol/L
What happens in the Jaffe reaction
Creatinine is reacted with alkaline picrate solution to form a complex which is read
What produces falsely elevated creatinine values in the Jaffe reaction
Interferences. Presence of noncreatine chromogens or Jaffe positive substances
Examples of Jaffe positive substances
Acetoacetic acid, pyruvic acid and hydantoin
What is different in the modified jaffe reaction
Absorbance is measured at two different pH levels
Urea:creatinine ratio
10:1 to 20:1
When would you see an increase in the ratio
Following GIT bleeding, fever and burns
When would you see a decrease in the ratio
Protein intake, severe liver disease
Rate that plasma is filtered in glomeruli
140ml/min
How is GFR measured
Clearance test, eGFR
What is clearance
The number of mls of blood cleared of a substance by per unit time
Formula for clearance
C=(UxV)/P
Limitations of clearance test
Expensive, difficult assay, invasive
