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Urea (view source)

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==Description==
 
==Description==
 
Urea is a form of nitrogenous waste formed from [[Ammonia|ammonia]] via the urea cycle in the liver.  It freely crosses lipid membranes and is filtered into the glomerular filtrate in the renal glomerulus.  A proportion of this filtered urea is reabsorbed passively before final excretion and it forms a vital of the concentration gradient needed to prevent passive diuresis.
 
Urea is a form of nitrogenous waste formed from [[Ammonia|ammonia]] via the urea cycle in the liver.  It freely crosses lipid membranes and is filtered into the glomerular filtrate in the renal glomerulus.  A proportion of this filtered urea is reabsorbed passively before final excretion and it forms a vital of the concentration gradient needed to prevent passive diuresis.
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Urea is principally a product of amino acid deamination in the liver. Urea is primarily excreted by the kidneys and is the most commonly used test of renal function with creatinine. References: [[NationWide Laboratories]]
    
==Clinical Significance==
 
==Clinical Significance==
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*Reduced synthesis with [[Portosystemic Shunt|porto-systemic shunts]], [[Hepatic Microvascular Dysplasia|microvascular dysplasia]] or liver failure.
 
*Reduced synthesis with [[Portosystemic Shunt|porto-systemic shunts]], [[Hepatic Microvascular Dysplasia|microvascular dysplasia]] or liver failure.
 
*A diet with a low protein content or malnutrition.
 
*A diet with a low protein content or malnutrition.
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== Small Animals ==
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=== Increased urea, renal azotaemia ===
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* Acute renal failure
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* Chronic renal failure
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=== Increased urea, prerenal azotaemia ===
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* Dehydration
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* Shock
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* High protein diet
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* Fever
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* Reduced cardiac output
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* Hyperthyroidism
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* Hypoadrenocorticism
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* Gastrointestinal haemorrhage
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=== Increased urea, postrenal azotaemia ===
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* Feline urological syndrome
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* Bladder rupture
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* Calculi
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* Neoplasia
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* Perineal herniation
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=== Causes of a low urea concentration ===
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* Polydipsia/polyuria (due to causes other than renal disease)
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* Hepatic insufficiency, especially portosystemic shunt
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* Low protein diet
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* Late pregnancy
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* Anabolic steroids
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=== Complementary tests ===
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Creatinine and phosphorus. Urine specific gravity, urinalysis, glomerular filtration rate and SDMA.
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== Equine ==
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=== Increased urea, prerenal azotaemia ===
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* Dehydration
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* Reduced renal perfusion
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* Congestive heart failure
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* Excessive muscle catabolism
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* High protein diet
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* Grass sickness
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=== Increased urea, renal azotaemia ===
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* Acute renal failure
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* Chronic renal failure
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=== Increased urea, postrenal azotaemia ===
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* Obstruction, ruptured bladder
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* Ruptured bladder in neonatal foals
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* Low urea concentrations
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* Hepatic insufficiency
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* Young foals (normal by 60 days)
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=== Complementary tests ===
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Creatinine and phosphorus. Urine specific gravity (<1.020 in a dehydrated or azotaemic horse suggests renal tubular dysfunction). Urine clearance or fractional electrolyte excretion ratios (renal
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tubular dysfunction).
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Test Codes - Please visit www.nwlabs.co.uk or see our current price list for more information
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== References ==
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Text referenced 'Nationwide Laboratories' [[NationWide Laboratories]]
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Small Animals: [[NationWide Laboratories]]
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Equine: [[NationWide Laboratories]]
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{{unfinished}}
 
{{unfinished}}
 
[[Category:Blood Biochemistry Changes]][[Category:To_Do_-_Blood]]
 
[[Category:Blood Biochemistry Changes]][[Category:To_Do_-_Blood]]
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