Assessment of renal function Flashcards
What clinical pathological markers can be used to assess renal function?
Bloods:
GFR
Blood conc of:
- urea
- creatinine
- Phosphorous
- SDMA
- potassium
FGF-23
Urinalysis:
USG
Fractional clearance
Proteinuria
What factors determine renal clearance?
GFR
Tubular reabsorption
Tubular secretion
How do you calculate renal clearance?
For what substances is clearance = GFR
If the substance is:
- filtered
- not reabsorbed
- not secreted (non-toxic, not plasma protein bound)
why is creatinine a better marker to use for assessing renal function than urea?
50% of Urea is reabsorbed to maintain medullary tonicity
Creatinine only changes in advanced renal disease
Why is it important to get a baseline creatinine level for each animal when using it to assess GFR?
A small change in creatinine (still within normal range) can be present with a large change in GFR
What does proteinuria suggest?
issue with filtration in glomerulus
What are the causes of pre-renal, renal and post renal proteinuria?
Pre renal - overload of proteins e.g., glucosuria in hyperglycaemia
Renal (glomerular) - damaged glomeruli
Renal (tubular) - unable to resorb normal amounts of filtered protein
Post renal - inflammatory, haeorrhagic conditions e.g. urinary tract inflammation
How is cystatin C used to assess renal function
Measured in blood - estimate of GFR
Measured in urine - should be completely resorbed in tubules, presence suggests tubular dysfunction/damage
What is fractional clearance?
the clearance of a substance (X) compared to creatinine that is neither absorbed or secreted
Example:
Volume depletion => sodium retained => fractional clearance falls
Tubular disease => sodium lost => fractional clearance rises
What is normal canine USG?
1.015 - 1.045
What is normal feline USG?
1.035 - 1.065
What is normal equine USG?
1.020 - 1.050
What is normal bovine USG?
1.025 - 1.045
How is USG used to determine if there is problem with concentrating ability?
Needs correlation with hydration state and/or azotaemia
What is azotaemia and indicator of in an animal with healthy renal function?
poor renal perfusion
What is azotaemia an indicator of in an animal with typical renal perfusion?
insufficient nephrons
Why is hyposthenuria and ADH problem and not a renal failure problem?
Kidney is functioning to produce dilute urine
ADH is not working to concentrate it in distal convoluted tubules and collecting duct
What are the types of urinary casts (cylinduria)?
Hyaline - protein
Cellular - RBC/WBC/epithelial
Granular - fine/coarse
Waxy - end product of degeneration
What does cellular casts in urine suggest?
disease process in tubules
What does granular casts in urine suggest
Degenerate cellular casts - implies longer stasis
Precipitated protein
Degenerate epithelial cells
What does waxy casts in urine suggest?
long period of stasis
Summarise the clinical pathology of renal failure
Non-regenerative anaemia
Increased plasma waste - urea, creatinine, phosphate, potassium
Inappropriately dilute USG
Urinalysis:
- evidence of pathology
- renal proteinuria
- tubular function
What is the outcome of acute kidney insufficiency?
Hyperkalaemia
What is the outcome of chronic kidney insufficiency
Progressive as functional nephrons decrease:
inappropriate USG => azotaemia => hyperphosphataemia, acidosis
Is this pre-renal or renal kidney insufficiency?
Pre-renal
Pre-renal or renal kidney insufficiency?
Renal
Pre-renal or renal kidney insufficiency?
Pre-renal
Pre-renal or renal kidney insufficiency?
Pre-renal
