Difference between revisions of "Azotaemia"

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== Introduction ==
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==Introduction==
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Azotaemia refers to an increase in the blood concentrations of '''urea''' and '''creatinine'''.  Azotaemia occurs almost exclusively with renal failure that results in an inability to excrete these two metabolic products. [[Urea]] and [[Creatinine]] vary in the extent of the increase induced by renal pathologies (creatinine can show substantial increases from baseline, whereas smaller increases in urea are  significant as levels generally increase by a much smaller factor) and also the timing of the increase - creatinine levels will rise and fall more quickly than changes in urea and can be more useful in monitoring responses to treatment as a resulyt of this feature.
  
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Azotaemia refers to biochemical evidence of increase in the blood concentrations of '''urea''' and '''creatinine'''. Azotaemia occurs almost exclusively with renal dysfunction, resulting in accumulation of these two, but not the only, waste products of protein metabolism. [[Urea]] and [[Creatinine]] vary in the extent of the increase induced by renal pathologies (creatinine can show substantial increases from baseline, whereas smaller increases in urea are significant as levels generally increase by a much smaller factor) and also the time taken for the increase. The severity of the increase in the urea concentration is considered to be proportional to the severity of the clinical syndrome, as urea (60D) is known to have distribution equal to the total body water, unlike that of creatinine. The severity in the increased concentration of creatinine, however, may not necessarily represent a severe damage to the kidneys. It is recommended that creatinine clearance and not the mere concentration of creatinine should be used as an indicator to judge the severity of illness.
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==Clinical Significance==
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Azotaemia may cause the clinical syndrome of [[Uraemia|'''uraemia''']], affecting multiple organ systems.  The causes of azotaemia are usually divided into pre-renal, renal and post-renal:
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*'''Pre-renal azotaemia''' occurs when the kidney receives insufficient oxygen to maintain its metabolism:
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**'''Dehydration/hypovolaemia''', reducing renal blood flow.
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**'''Heart failure''' results in a reduced cardiac output, reducing renal blood flow.
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**'''Anaemia''' reduces the amount of oxygen delivered to the kidneys.
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**'''Portal hypertension''' may result in splanchnic pooling of blood and reduced renal blood flow.
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*'''Renal azotaemia''' results from direct insults to the kidney:
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**'''Exogenous toxins''' including heavy metals, [[Aminoglycosides|aminoglycosides]], [[Tetracyclines|tetracyclines]], polymixin B, cisplatin, lilies in cats and grapes in dogs.
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**'''Endogenous toxins''' including haemoglobin, myoglobin and calcium.
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**Infection as in '''pyelonephritis''', '''interstitial nephritis''' (as caused by [[Leptospirosis - Cats and Dogs|''Leptospira spp.'']] or '''granulomatous nephritis''' (as caused by the dry form of [[Feline Infectious Peritonitis]]).
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**'''Glomerulonephritis''' and '''[[Amyloidosis|amyloidosis]]'''.
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**'''Neoplasia''', including adenocarcinoma in dogs and lymphoma in cats.
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*'''Post-renal azotaemia''' results from obstructions to the urinary tract:
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**'''[[Urolithiasis - Small Animal|Urolithiasis]]'''
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**'''Rupture of the urinary tract''', often due to trauma and causing [[Uroabdomen|uroabdomen]].
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**'''Neoplasia''', including transitional cell carcinoma of the bladder and prostatic neoplasia.
  
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== Clinical Significance ==
 
  
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Azotaemia may cause the clinical syndrome of [[Uraemia|'''uraemia''']], affecting multiple organ systems, and may involve retention of an array of different toxins in the body, which a healthy kidney would have excreted in the urine.
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[[Category:Blood Biochemistry Changes]]
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The causes of azotaemia can broadly be classified into pre-renal, renal and post-renal, however clinical differentiation is always challenging, as the manifestation is almost always, overlapping.
 
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=== Pre-renal azotaemia ===
 
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This occurs when the kidney receives insufficient oxygen via blood flow to maintain its normal metabolic processes. Conditions that can cause this include:
 
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*'''Dehydration/hypovolaemia''', which reduces renal blood flow.
 
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*'''Heart failure''' which results in a reduced cardiac output, thereby reducing renal blood flow.
 
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*'''Anaemia''' reduces the amount of oxygen delivered to the kidneys.
 
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*'''Portal hypertension''' may result in splanchnic pooling of blood and reduced renal blood flow.
 
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=== Renal azotaemia ===
 
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This occurs following a direct insult to the kidney from several possible causes including:
 
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*'''Exogenous toxins''' including heavy metals, [[Aminoglycosides|aminoglycosides]], [[Tetracyclines|tetracyclines]], polymixin B, cisplatin, antifreeze ([[Ethylene Glycol Toxicity|ethylene glycol]]), [[NSAIDs]], lilies in cats and grapes in dogs.
 
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*'''Endogenous toxins''' including haemoglobin, myoglobin and calcium.
 
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*Infections such as '''pyelonephritis''', '''interstitial nephritis''' (as caused by [[Leptospirosis - Cats and Dogs|''Leptospira spp.'']] or '''granulomatous nephritis''' (as caused by the dry form of [[Feline Infectious Peritonitis]]).
 
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*'''Glomerulonephritis''' and '''[[Amyloidosis|amyloidosis]]'''.
 
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*'''Neoplasia''', notably [[Adenocarcinoma|adenocarcinoma]] in dogs and [[Lymphoma|lymphoma]] in cats.
 
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=== Post-renal azotaemia ===
 
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This occurs following obstructions within the urinary tract:
 
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*'''Urolithiasis'''
 
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*'''Rupture of the urinary tract''', often due to trauma and causing [[Peritonitis - Cats and Dogs|uroabdomen]].
 
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*'''[[Neoplasia - Pathology|Neoplasia]]''', including transitional cell carcinoma of the bladder and prostatic neoplasia.
 
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[[Category:Blood_Biochemistry_Changes]] [[Category:Urological_Diseases_-_Dog]]
 

Revision as of 10:58, 3 November 2010

Introduction

Azotaemia refers to an increase in the blood concentrations of urea and creatinine. Azotaemia occurs almost exclusively with renal failure that results in an inability to excrete these two metabolic products. Urea and Creatinine vary in the extent of the increase induced by renal pathologies (creatinine can show substantial increases from baseline, whereas smaller increases in urea are significant as levels generally increase by a much smaller factor) and also the timing of the increase - creatinine levels will rise and fall more quickly than changes in urea and can be more useful in monitoring responses to treatment as a resulyt of this feature.

Clinical Significance

Azotaemia may cause the clinical syndrome of uraemia, affecting multiple organ systems. The causes of azotaemia are usually divided into pre-renal, renal and post-renal:

  • Pre-renal azotaemia occurs when the kidney receives insufficient oxygen to maintain its metabolism:
    • Dehydration/hypovolaemia, reducing renal blood flow.
    • Heart failure results in a reduced cardiac output, reducing renal blood flow.
    • Anaemia reduces the amount of oxygen delivered to the kidneys.
    • Portal hypertension may result in splanchnic pooling of blood and reduced renal blood flow.
  • Renal azotaemia results from direct insults to the kidney:
    • Exogenous toxins including heavy metals, aminoglycosides, tetracyclines, polymixin B, cisplatin, lilies in cats and grapes in dogs.
    • Endogenous toxins including haemoglobin, myoglobin and calcium.
    • Infection as in pyelonephritis, interstitial nephritis (as caused by Leptospira spp. or granulomatous nephritis (as caused by the dry form of Feline Infectious Peritonitis).
    • Glomerulonephritis and amyloidosis.
    • Neoplasia, including adenocarcinoma in dogs and lymphoma in cats.
  • Post-renal azotaemia results from obstructions to the urinary tract:
    • Urolithiasis
    • Rupture of the urinary tract, often due to trauma and causing uroabdomen.
    • Neoplasia, including transitional cell carcinoma of the bladder and prostatic neoplasia.
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