Urine - hemoglobin
Hemoglobin is a molecule attached to red blood cells in the blood. Normally, unbound hemoglobin is not excreted in the urine. Hemoglobinuria is the presence of free, unbound hemoglobin in the urine, which is not normal.
How the test is performed
You need to collect a “clean-catch” (midstream) urine sample. To obtain a “clean-catch” sample, 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 (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant.
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 your 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. 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 displace the bag, causing an inability to obtain the specimen. The urine is drained 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. 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.
Why the test is performed
This test may be used to help diagnose:
- hemolytic anemia
- the breakdown of red blood cells from a transfusion reaction or other process
Hemoglobin is composed of a molecule called heme, and a protein called globin. Together, they form a molecule called hemoglobin, which is within red blood cells. The purpose of hemoglobin is to transfer oxygen and carbon dioxide.
In the lungs, the hemoglobin picks up molecules of oxygen. Then, the hemoglobin and oxygen are carried within red blood cells to tissues that need oxygen. The hemoglobin gives up the oxygen and picks up carbon dioxide from the tissue - which is then carried back to the lungs again in a continuous cycle.
Red blood cells have an average life span of 120 days. After this time, they are broken down into their components for reassembly into a new red blood cell. This typically takes place in the spleen, bone marrow, and liver. If the red blood cells are hemolyzed (broken down) in the blood vessels, the components are free in the blood stream. Free hemoglobin is typically reprocessed. If the level of hemoglobin in the blood rises too high, then hemoglobin begins to appear in the urine.
Normally, hemoglobin does not appear in the urine.
What abnormal results mean
Hemoglobinuria may be a result of any of the following:
- acute glomerulonephritis
- transfusion reaction
- crushing injury (more likely from myoglobin than hemoglobin)
- paroxysmal nocturnal hemoglobinuria
- sickle cell anemia
- hemoglobin C disease
- hemoglobin SC disease
- renal tumor
What the risks are
The test has no risks in adults or children, but occasionally an infant may develop a mild skin rash from the adhesive on the collection bag.
by Dave R. Roger, M.D.