Azotemia Flashcards
Definition
- renal disease
- renal insufficiency
- renal failure
Renal disease: damage or functional impairment of kidneys
varying severity
Renal insufficiency: functional impairment not severe enough to cause azotaemia, but sufficient to cause loss of renal reserve
Renal failure: functional impairment severe enough to cause azotaemia and impairment of urine concentrating
Glomerular filtration rate (GFR)
Flow rate of filtered fluid through the kidneys
Defines the excretory function of the kidneys
Urinalysis
- Dipstick analysis
- Urine concentration (specific gravity measurement)
- Sediment examination
- Urine protein:creatinine ratio
Urine concentration
- refractometer
- Gold standard is osmolality
- Measure of the number of particles in a solution
- Influenced by the number & size of the particles
- -> Glucosuria –> increase in specific gravity
Urine specific gravity
- Interested in concentration of urine relative to plasma
- Hyposthenuria – 1.000 to 1.007
- Isosthenuria – 1.008 to 1.012
- Minimally concentrated urine – 1.013 to 1.030
- Hypersthenuria – 1.033 to 1.055
Azotaemia
Abnormal increase in the concentration of non-protein nitrogenous wastes in blood
Urea
Synthesised in the liver
Excreted by the kidney
Concentration of urea in renal medulla helps maintain solute gradient
Serum levels affected by:
- Species
- Age
- Liver function
- Dietary protein content (including GI bleeding)
- Endogenous protein catabolism
- Renal function
Creatinine
- Synthesised by breakdown of creatine in skeletal muscle
- Produced at constant rate
- Depends on muscle mass
- Excreted unchanged by kidneys
Serum concentration increased with:
- Reduced renal clearance (↓GFR)
Serum concentration decreased in:
- Reduced muscle mass
Creatinine better indicator of GFR than urea BUT relationship is not linear
Azotaemia does not develop until GFR has decreased to 25%
Creatinine and GFR
- relationship
- limitations
Creatinine better indicator of GFR than urea BUT relationship is not linear
Azotaemia does not develop until GFR has decreased to 25%
Limitations
- Does not tell you why the GFR has fallen
- Does not discriminate between:
- Causes of azotaemia
- Acute or chronic renal failure
- Reversible or irreversible renal failure
ureamia and azotemia
All uraemic patients are azotaemic but not all azotaemic patients are uraemic
Uraemia CS
Inappetance Depression Vomiting/ Nausea Halitosis Diarrhoea
Causes of azotemia
- pre-renal: inadequate blood flow
- renal: intrinsic renal failure
- post renal: Post-renal obstruction or rupture of urinary tract
azotemia does not equal renal disease
Differentiating the cause of azotemia
History:
- pollakiuria or stranguria (post-renal)
Clinical examination:
- Evidence of dehydration (pre-renal +/- renal +/- post-renal)
- Grossly enlarged bladder on palpation (post-renal)
- Difficult or impossible to pass urinary catheter (post-renal)
- Localised subcutaneous fluid around perineum or ventral abdomen (post-renal)
- Free peritoneal fluid (post-renal)
Urinanalysis:
- Specific gravity (before fluid therapy):
- -> Hypersthenuric (pre-renal)
- -> Remember that drugs & some non-renal illnesses can cause dehydration and pre-renal azotaemia with dilute urine
- Urine sediment (before fluid therapy):
- -> Active sediment with tubular casts (renal)
- -> Haematuria (renal or post-renal)
Acute renal failure
- what
- causes
- risk factors (3)
Sudden, often reversible reduction of the elimination and metabolic functions of the kidneys
Often due to a toxic or ischaemic insult
Kidneys are at high risk of damage:
- Huge blood flow
- Toxins may be secreted/reabsorbed by tubular cells
- Potential concentrating effects of toxins in urine
Play a role in biotransformation of drugs/toxins
Acute renal failure causes
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