Laboratory Diagnosis of Renal Patients Flashcards
What are the functions of the kidney?
> Excretion of nitrogenous waste (urea and
creatinine)
Regulate body water and solute concentration
in the urine
Regulate electrolyte composition
– sodium, chloride, potassium, calcium, magnesium, sulphate and phosphate ions
Regulation of acid-base balance
– Excretion of H+ and conservation of HCO
Endocrine function
– Produce erythropoietin, renin and active
metabolites of vitamin D.
Elimination of toxic substances
– The kidneys may eliminate and
concentrate chemicals, pollutants, food
additives and drugs within the urine.
What is glomerular filtration rate (GFR)?
Rate fluid moves from plasma to the glomerular filtrate
Define azotemia
An increase in the non-protein nitrogenous compounds, usually urea nitrogen (UN) and/or creatinine or uric acid (birds) in the blood
What is uremia?
Complex of clinical signs and biochemical abnormalities (azotemia) associated with the loss of functional nephrons
What are the clinical signs associated with uremia?
> Anorexia > Vomiting > Diarrhoea > GI haemorrhage > Ulcerative stomatitis > Bruxism in ruminants
What is the relevant biochemistry in regards to renal disease?
> UN > Creatinine > Phosphorus > Calcium > Sodium > Chloride > Potassium > Acid base > Protein
Where is urea produced and excreted?
Urea is produced in the liver via the urea cycle and excreted by the kidney thus levels will be influenced by liver function and protein levels.
Where is creatinine created?
Derived from creatine in muscles, and thus will be influenced by muscle mass
What is UN?
Urea nitrogen
Where goes UN come from?
Synthesised from ammonia (waste product of protein catabolism) via the urea cycle in the liver
What influences UN levels?
Protein intake
Explain the physiology of UN..
Passively filtered by the glomerulus and concentration in the filtrate is the same as blood. Increased UN is largely by result of decreased filtration.
In cattle, which is the better indicator of renal disease, creatinine or urea and why?
Creatinine. In cattle, urea is excreted into the rumen and converted to ammonia and then amino acids. If the animal is anorexic, all urea will be excreted via the GIT and not the kidneys and thus anorexic ruminants with renal failure may have a normal UN.
How can you tell if you have a ruptured bladder?
Abdominocentesis, test the fluid for creatinine levels. If creatinine is higher than serum levels then consistent with uroabdomen.
What are the three types of azotemia?
Prerenal
Renal
Poster all
What is the underlying mechanism for prerenal azotemia?
As a result of reduced renal perfusion or increased protein catabolism
What is the underlying mechanism of renal azotemia?
Due to renal disease and presence of nonfunctional nephrons
What is the underlying mechanism for postrenal azotemia?
Caused by interference with excretion of urine (obstruction or postrenal leakage)
Give some example of causes of pre-renal azotemia..
Increased protein catabolism which may be secondary to gastric or small bowel haemorrhage, necrosis, starvation or corticosteroids
High protein diets
Reduced renal perfusion with haemoconcentration MOST COMMON
What should the USG be in prerenal azotemia and why?
High because ADH response occurs and the kidneys can concentrate urine
What would you clinically see with post-renal azotemia?
Oliguria or anuria
What may falsely increase USG?
Glucose or protein in the urine
If urea and creatinine are increase in the serum then USG should be at least…
- 030 in the dog
- 035 in the cat
- 025 in the horse or ruminant
Define isosthenuria
Fixed USG 1.008-1.012, kidneys are not concentrating or diluting urine so osmolality is the same as glomerular filtrate
