Transillumination is the shining of a light through a body area or organ to check for abnormalities.
How the Test is Performed
The room lights are dimmed or turned off so that the area of the body may be seen more easily. A bright light is then pointed at that area. Areas where this test is used include the head, scrotum, chest of a premature or newborn infant, or breast of an adult female.
Transillumination is also sometimes used to find blood vessels.
How to Prepare for the Test
No preparation is necessary for this test.
How the Test will Feel
There is no discomfort with this test.
Why the Test is Performed
This test may be done along with other tests to diagnose:
In newborns, a bright halogen light may be used to transilluminate the chest cavity if there are signs of a collapsed lung or air around the heart. (Transillumination through the chest is only possible on small newborns.)
In general, transillumination is not a good test for any of the disorders above. Further tests, such as an x-ray or ultrasound, are needed to confirm the diagnosis.
Normal findings depend on the area being evaluated, and the normal tissue of that area.
What Abnormal Results Mean
Areas filled with abnormal air or fluid light up when they should not. For example, in a darkened room, the head of a newborn with possible hydrocephalus will light up when this procedure is done.
When done on the breast:
- Internal areas will be dark to black if there is a lesion and bleeding has occurred (because blood does not transilluminate).
- Benign tumors tend to appear red.
- Malignant tumors are brown to black.
There are no risks associated with this test.
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Last reviewed 10/14/2013 by George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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