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    Transillumination

    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
    • Breast of an adult female

    Transillumination is also sometimes used to find blood vessels.

    In some locations in the stomach and intestine, the light can be seen through the skin and tissues at the time of upper endoscopy and colonoscopy.

    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 an accurate enough test to rely on. Further tests, such as an x-ray, CT scan, or ultrasound, are needed to confirm the diagnosis.

    Normal Results

    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.

    Risks

    There are no risks associated with this test.

    Open References

    References

    Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW. Examination techniques and equipment. In: Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW, eds. Seidel's Guide to Physical Examination. 10th ed. St Louis, MO: Elsevier; 2023:chap 3.

    Griswold K, Srinivas GL. Physical examination of the healthy newborn. In: Martin RJ, Fanaroff AA, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 12th ed. Philadelphia, PA: Elsevier; 2025:chap 27.

      • Infant brain test

        Infant brain test - illustration

        Transillumination is the shining of a bright light through a body cavity or organ for diagnostic purposes. Transillumination can be used on the head, scrotum, or chest in the premature or newborn infant, or the breast in an adult female.

        Infant brain test

        illustration

        • Infant brain test

          Infant brain test - illustration

          Transillumination is the shining of a bright light through a body cavity or organ for diagnostic purposes. Transillumination can be used on the head, scrotum, or chest in the premature or newborn infant, or the breast in an adult female.

          Infant brain test

          illustration

        Tests for Transillumination

         

        Review Date: 7/13/2025

        Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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