| Subject | Contents |
| Definition | The shining of a light through a body cavity or organ. |
| Alternative Names | |
| How the test is performed | The room lights are dimmed or turned off so that the appropriate part may be seen more easily. A bright light is then pointed at a cavity or organ, typically the head, scrotum , or chest in the premature or newborn infant or the breast in an adult female.
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| How to prepare for the test | No preparation is necessary for this test. |
| How the test will feel | There is no discomfort associated with this test. |
| Why the test is performed | This test is most commonly performed on newborns or infants with hydrocephalus , or males suspected of having a hydrocele . The test may also be performed on breast tissue to detect lesions and/or cysts . In newborns, a bright halogen light may be used to transilluminate the chest cavity if it is suspected they have a pneumothorax . Transillumination through the chest is only possible on small newborns. Diagnosis of pneumothorax is always confirmed by chest X-ray . In general, transillumination is not a particularly good test for any of these disorders, and further tests, such as an X-ray or ultrasound, are needed to confirm the diagnosis.
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| Normal Values | Normal findings depend on the area being evaluated, and the normal tissue of that region. |
| What abnormal results mean | Areas filled with air or fluid that is not native to that location have increased light transmission and transilluminate when they should not. For example, in a darkened room, a newborn infant's head can be seen to light up brightly when transilluminated if there is excess fluid present (suggesting hydrocephalus). Results specific to the breasts include: If there is a lesion and bleeding has occurred, those internal areas will be dark to black, because blood does not transilluminate.Benign tumors tend to appear red. Malignant tumors are brown to black. |
| What the risks are | There are no risks associated with this test. |
| Special considerations | |
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