Biochemical measures in renal disease Flashcards
What are the properties of a good marker of GFR?
Freely filtered but not reabsorbed nor secreted
Urea is the end product of what?
Protein metabolism
Where does the urea cycle occur?
Within the liver
What biochemical marker is commonly used to assess GFR?
Creatinine
Creatinine is the end product of what?
Muscle protein metabolism
What is the drawback of using creatinine as a biochemical marker?
Not sensitive to changes in GFR (60-120) unless they are marked (
How can small changes in GFR be detected?
Urinary creatinine clearance
Which clinically significant factors will affect GFR? How are these estimated?
Muscle mass and diet
Estimated from age, ethnicity and sex
Define clearance
Volume of plasma cleared of a substance per minute
State the equation used to calculate urinary creatinine clearance
(Urine creatinine conc x urinary output) / (Serum creatinine conc x duration of collection)
Is creatinine concentration higher in urine or serum? Why is this relevant for carrying out calculations?
Urine
Must remember to make units the same
Which factors are considered in the equation used to calculate eGFR?
Serum creatinine
Age
Sex
Ethnicity
How is chronic kidney disease classified based on eGFR?
1 (kidney damage with normal/high GFR) - >90
2 (kidney damage with mildly low GFR) - 60-89
3 (moderately low GFR) - 30-59
4 (severely low GFR) - 15-29
5 (kidney failure) -
How are each of the chronic kidney disease classifications managed?
1 - treatment of co-morbid, risk reduction
2 - estimate progression
3 - evaluating and treating complications
4 - preparation for kidney replacement therapy
5 - replacement
The functionality of which part of the nephron is being assessed with GFR?
Glomerulus
Plasma proteins are normally found in the urine. T/F
False
How can proteinuria be measured?
24 hour collection
Protein:creatinine ratio (avoids errors due to dehydration status)
Significant glomerular damage is indicated by proteinuria over which level?
> 150mg/day
List the different types of proteinuria?
Overflow (bence jones)
Glomerular (albuminuria)
Tubular (microglobulinuria)
Secreted (tamm-horsfall)
Describe overflow proteinuria
An increase in serum protein to the level that the mechanisms of reabsorption within the tubules reach transport maximum and thus cannot reabsorb all protein
Describe glomerular proteinuria
Protein levels are normal but glomerular damage allows all proteins to be filtered thus overwhelming mechanisms of reabsorption within the tubules meaning that it can’t all be reabsorbed
What is multiple myeloma? Which type of proteinuria does it cause?
Malignancy of the plasma cells which causes overproduction of antibodies and light chain proteins resulting in overflow proteinuria
What is the characteristic appearance of the skull in multiple myeloma?
Pepper pot
How is multiple myeloma diagnosed?
Bone marrow aspirate & analysis
Protein electrophoresis
Skeletal survey
What is nephrotic syndrome? Which type of proteinuria does it cause?
Non-specific kidney disorder characterised by large proteinuria, hypoalbuminaemia and oedema. Glomerular
Why does oedema occur in nephrotic syndrome?
Loss of protein in the urine causes hypoalbuminaemia and thus alters oncotic pressures. The reduced oncotic pressure means more fluid is left within the interstitium (i.e oedema)
What is microalbuminuria?
Excretion of albumin in abnormal quantities but still below the level of detection by dipstick testing
Microalbuminuria is the earliest sign of which complication of which disease? How is it treated?
Diabetic nephropathy
ACE inhibitors
Describe the sliding scale of proteinuria from least protein to most protein
Microalbuminuria
Proteinuria
Nephrotic
How can proteinuria be detected?
Dipstick
PCR (protein creatinine ratio)
Total protein
ACR (albumin creatinine ratio)
Tubular function problems can be divided into three categories. Name them and there common causes
Pre-renal - reduced kindey perfusion (blood loss)
Renal - intrinsic damage (glomerulonephritis, toxins)
Post-renal - obstruction (stones, malignancy)
What is oliguria?
Peeing an abnormally small amount
What is a normal serum osmolarity?
270-300
Should urinary or serum osmolarity be higher?
Urinary - if they are equal it indicates tubular damage
Are the kidney tubules working in pre-renal or renal failure?
Tubules are working in pre-renal failure
Which biochemical results would indicate intrinsic renal damage?
High sodium
Low urine:serum urea
Low urine:serum osmolarity
