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Myoglobinuria Equine Disease

Myoglobinuria is the equine disease caused bybpresence of the protein myoglobin in the urine.  Normally myoglobin is found in muscle cells and its main function is to transport oxygen to the cells much like that of Haemoglobin.  These two proteins both contain haem, but have different affinities for oxygen due to their different structures.  When muscles become damaged, myoglobin is released into the bloods circulation and transported to the kidneys to be excreted.  If myoglobin is found in the urine this is myoglobinuria and it can be concluded that there has been damage caused to the muscles.  Myoglobin enters the renal tubules, causing a blockage which leads to acute renal failure. 
Once muscles are damaged, the equine disease myoglobinuria ensues.  Trauma is major contributor to myoglobinuria.  Normally there are low levels of myoglobin in the urine, but this does not indicate myoglobinuria.  When myoglobin is released by muscle cells, proteins called haptoglobins bind to it.  Saturation occurs rapidly, leaving excess myoglobin in the blood.  This free myoglobin enters the renal tubules and may precipitate causing further damage. 
Myoglobinuria can be detected by darker urine.  If a dipstick is used to test the amount of urine in the blood, a positive result can mean both myoglobinuria and haematuria.  These must not be confused! After a microscopy on the urine, it will become clear which is which.  If there is a lack of red blood cells in a positive blood test then this is myoglobinuria.  Immunoassays may also test directly for myoglobinuria.

Myoglobinuria is an equine disease that may have no symptoms.  The disease can be detected easily by the colour of the urine (rusty), or by any signs of muscle pain or weakness.

Any sort of muscle damage or destruction is responsible for  the equine disease myoglobinuria.

  • Meyer-Betz disease – muscle pain and weakness and myoglobinuria after high energy exercise
  • Snake venom caused by snake bites
  • Drugs: Heroin, ethylene glycol or diazepam
  • Genetic Disorders
  • Myocarditis – inflammation of the heart muscle
  • Burns
  • Myositis
  • Rhabdomyolysis
  • Status epilepticus – continuous seizing

Normally small amounts of myoglobin can be filtered and excreted by the kidneys.  However if too much is released into the blood (due to muscle damage), they cause an obstruction in the renal tubules.  This is then detected in the urine causing the equine disease mysoglobinuria.  This can lead to acute tubular necrosis (death of kidney cells) and acute renal failure.

Detection:  Blood sample is taken and centrifuged.  The serum of myoglobinuria is clear whilst the serum of hemoglobinuria after is pink.
Once the equine disease myoglobinuria is determined prompt fluid rehydration aids in the initial control of myoglobinuria.
Any horse with the suspected disease myoglobinuria or rhabdomyolysis should be admitted for prompt intravenous hydration. Initial treatment prevents the precipitation of myoglobin in the urine by inducing diuresis.  Saline must be administered as soon as possible to horses with suspected myoglobinuria or rhabdomyolysis because early hydration is the key to rectify acute renal failure. 



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