Flashcards in Lab Dx Urinary Dz Deck (61)
What affects GFR?
Renal perfusion and plasma flow
- increase in non-protein nitrongenous compounds (usually urea nitrogen (UN) and or creatinine or uric acid (birds)) in the blood
Uraemia = sick from azotaemia (every urea mic animal is azotaemic but NOT vice versa)
Clinical signs of uraemia
- GI haemorrhage
- ulcerative stomatitis
- bruxism in ruminants
What causes loss of kidney function?
Loss of number of functioning nephrons (not a decrease function of each individual)
Which biochem parameters are related to renal function?
- acid base
Which 2 diagnostics are more important for evaluating renal function?
Serum/plasma chemistry and urinalysis CONCURRENTLY
Most important biochem results
> UN (urea nitrogen)
- indicate GFR (^conc in blood if GFR v)
Where is urea produced and where does it travels?
- urea produced in liver from ammonia (ammonia very toxic, urea bit less toxic)
- excreted by kidney
- levels affected by liver function and protein levels
What affects creatinine levels
Derived from creatine in muscles, influenced by muscle mass
What causes ^ urea
Protein meal or decrased filtration (GFR)
Is urea excreted in feaces?
How does excretion of urea and creatinine differ?
Creatinine not reabsorption
- urea can reabsorb in collecting duct
Does urea equilibrate in body?
Once in vascular diffuses through body water in 90mins
How is UN excreted?
- Renal excretion most important route
- passively filtered by glomerulus (conc filtrate same as blood)
- passively diffuses with water from tubular luman back into blood
- amount absorbed inversely proportional to urine flow (v urine flow ^ absoroption and ^ blood levels)
Is Urea measurement reliable in ruminants ?
- NO (Use creatinine)
- cattle severe renal dz can compensate urea levels as excreted into rumen and used to produce protein
- if anorectiv all urea will be excreted via GIT not kidneys
Creatinine sources - what influences levels? How easily does this equilibrate?
- non-enzymatic conversion of creatine stores ini muscle
- constant rate of conversion (influenced by muscle mass and disease)
- will distribute in body water but very slowly cf. urea
How do creatinine and urea levels change with a ruptured bladder?
- abdo fluid concentrations creatinine > serum levels
- difference with serunm lasts longer cf. differneces in urea levels
Is creatinine a sensitive indicator of kidney function?
NO 3/4 nephrons lost before parameters change
- more sensitive cows and horse
- not at all sensitive birds
whY IS Creatinine such a poor indicator in birds ?
- uric acid produced instead
- hyperuriceamia does occour but not very sensitive
- may also occour during ovulation and after meal
3 types of azotaemia
> prerenal azotaemia
- v GFR d/t v renal perfusion (poor BP -> vasoconstriction and ULTIMATELY ischaemia)
- or ^ protein catabolism
- v GFR d/t non functioning nephrons
- interference with excretion of urine (obstruction/postrenal leakage)
How can prerenal azotaemia be Dx?
Urine SG low shows no functioning nephrons and poor concentration
- if urine SG normal then must be pre renal
Causes of prerenal azotaemia
- ^protein catabolism
- gastric or SI haemorrhage / necrosis / starvation / corticosteroids / high protein diet
- reduced renal perfusion == haemoconcentration MOST COMMON CAUSE
- dz causing pre/post renal azotaemia 2* affect the kidneys -> renal azotaemia
- USG high d/t ADH response occouring -> concentration of urine
Why dos USG increase with pre-renal azotaemia?
- ADH response -> kidney concentrates urine
Causes of Post renal azotaemia. CLinical signs?
- obstruction/post rental leakage
- oliguria/anuria clinically
- USG may vary
- UN and creatinine return to normal once obstruction releved
What is USG compared with?
Creatinine and urine on serum /plasma
What is USG and what is it a measure of?
- ratio of refractive index urine cf. ater
- depends on particle size, weight and number
- reflects osmolality (very expensive machine needed to measure this!)
- falsely increased by glucose and protein
What is a normal USG?
No reference interval
- based on expectation
- range 1.001 - 1.065 in healthy animals (1.080 in cats)
- concentrating ability neonates is poor
What may falsely increase USG?
- glucose (some effect on osmolality but not much)
- protein (no effect on osmolality but 3+ increase ~= 0.004 change)