Myoglobin - urine

Alternative names
Urine myoglobin

Definition

This is a test to detect the presence of myoglobin in urine.

Myoglobin is a protein in heart and skeletal muscles. When a muscle is exercised, it uses up available oxygen. Myoglobin has oxygen bound to it, thus providing an extra reserve of oxygen so that the muscle can maintain a high level of activity for a longer period of time.
When muscle is damaged, the myoglobin is released into the bloodstream. It is filtered out of the bloodstream by the kidneys, and eliminated in urine. In large quantities, myoglobin can damage the kidney and break down into toxic compounds, causing kidney failure.

How the test is performed

A “clean-catch” (midstream) urine sample must be obtained. To perform a clean-catch, men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well.

As you start to urinate, allow a small amount to fall into the toilet bowl first (this clears the urethra of contaminants), and then catch about 1 to 2 ounces of urine in the container. Give the container to the health care provider or assistant.

For infants:
Thoroughly wash the area around the opening where the urine flows from. Open a Urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed inside the bag and the adhesive attached to the skin. For females, the bag is placed over the lips of the vagina.

Place a diaper over the infant (bag and all). Check your baby frequently and remove the bag after the infant has urinated into it. For active infants, this procedure may take a couple of attempts-lively infants can easily displace the bag. The urine is then poured into a container for transport back to the health care provider.

How to prepare for the test
No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel
The test involves only normal urination which should cause no discomfort.

Why the test is performed
Myoglobin levels may be obtained when muscle damage, including skeletal and heart muscle damage, is suspected.

Normal Values
A normal urine sample does not have myoglobin. (Sometimes a normal result is reported as “negative”.)

What abnormal results mean
The presence of myoglobin in the urine may indicate:

     
  • skeletal muscle ischemia (blood deficiency)  
  • skeletal muscle trauma  
  • skeletal muscle inflammation (myositis)  
  • heart attack  
  • muscular dystrophy  
  • rhabdomyolysis  
  • malignant hyperthermia (very rare)

What the risks are
There are no risks.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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