Transillumination is the shining of a light through a body cavity or organ.

This test may be done along with other tests to diagnose:

• Hydrocephalus in newborns or infants
• Hydrocele in males
• Breast lesions or cysts in females

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.)

The room lights are dimmed or turned off so that the appropriate part of the body may be seen more easily. A bright light is then pointed at a location on the body, typically 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.

No preparation is necessary for this test.

There is no discomfort associated with this test.