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Myoglobin - urine

Definition

Urine myoglobin 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

Collect a "clean-catch" (midstream) urine sample. To obtain a clean-catch sample, men or boys should 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 to clear the urethra of contaminants. Then, put a clean container under your urine stream and catch 1 to 2 ounces of urine. Remove the container from the urine stream. Cap and mark the container and give it to the health care provider or assistant.

For infants:

Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia.

Diaper as usual over the secured bag. This procedure may take a couple of attempts -- lively infants can displace the bag, causing the specimen to be absorbed by the diaper. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

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: