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Transillumination is the use of a strong light as a noninvasive tool for bedside diagnosis and aiding in procedures. By shining a bright light through an area of the body or an organ, one can diagnose abnormal air, fluid, or a nonsolid mass. One can also localize vessels, verify urine in the bladder, and aid in insertion in many procedures.

  1. Procedures

    1. Localize an artery or vein for vessel cannulation or blood sampling.

    2. Bladder aspiration. Transillumination verifies the presence of urine in the bladder and shows the size and location of the bladder.

    3. Cannulation of umbilical vessels. Transillumination identifies path of the vessels and can identify a false passage of an umbilical catheter.

    4. Aid in oro/nasoduodenal feeding tube insertion (by gauging distension of stomach with air).

    5. Chest tube thoracostomy/pericardiocentesis. Transillumination can document the success of air removal in a pneumothorax or in a pneumopericardium.

    6. Serial transillumination for infants at high risk for pneumothorax.

  2. Diagnostic. Air or fluid or nonsolid masses will light up brightly when transilluminated. Solid masses will appear dark. Normally there is a 2-cm area of lucency around the probe. If there is more than 2-cm lucency, the test is abnormal and further testing may have to be done.

    1. Chest abnormalities. Air leaks in infants (such as pneumothorax, pneumomediastinum, and pneumopericardium) can be suspected and some diagnosed at the bedside with transillumination. The thin wall of the infant's chest makes it easy to transilluminate, and as little as 10 mL of free air can be detected. Obtain a baseline transillumination on any infant at a high risk for an air leak.

    2. Abnormalities in the head. Such as hydrocephaly, intracranial hemorrhage, subdural effusion, subdural hematoma, skull fractures, hydrocephalus, hydranencephaly, anencephaly, porencephaly, encephalocele, and large cerebral cysts. Transillumination of the skull is known as skull diaphanoscopy. It can be used as a screening tool for macrocephaly.

    3. Differentiate cystic from solid masses. Such as cystic hygroma, a congenital macrocystic lymphatic malformation commonly found in the left base of the neck, that reveals complete transillumination.

    4. Abdominal abnormalities. Such as ascites, distended bowel, pneumoperitoneum, cysts, perforated bowel in male infants with a patent processus vaginalis.

    5. Genitourinary abnormalities. Such as distended bladder, hydrocele, hydronephrosis, cystic kidneys.




Light source such as mini–light-emitting diode light, high-intensity fiber optic light source, commercially available transilluminators (eg, Veinlite, TransLite LLC, Sugarland, TX; Pediascan, Sylvan Fiberoptics, Irwin, PA), simple otoscope with light, disposable plastic cover or sterile glove to cover light source for aseptic technique, alcohol swab.




Clinical examination is always necessary with transillumination. It is best to transilluminate the contralateral side of the body to compare changes.

  1. Clean end of light source with an alcohol swab and cover with either a disposable plastic cover or sterile glove.

  2. Turn the lights in the room down and set light on the lowest intensity and increase as needed. Limit skin contact time with light source.


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