Shedding Light on Transillumination

Written by Erica Roth | Published on August 7, 2012
Medically Reviewed by George Krucik, MD

What Is Transillumination?

Transillumination is test that can identify abnormalities in an organ or body cavity. The test is performed in a dark room. The doctor shines a bright light at a specific body part to see its structures beneath your skin.

The test is painless and requires no special preparation.

Why Transillumination Is Performed

Transillumination can play a role in diagnosing certain medical conditions. However, the test is almost always used in conjunction with other procedures to confirm a diagnosis. Transillumination may be used along with other imaging tests, such as an ultrasound or MRI, or may precede a biopsy.

Certain conditions may be visible through transillumination, including:

  • cysts or lesions in a woman’s breast
  • hydrocele (an opening between the scrotum and the peritoneal cavity in newborn males)
  • a collapsed lung in newborn babies
  • hydrocephalus (a fluid accumulation in the brain of an infant)
  • hydranencephaly (the absence of brain matter in an infant)

Hydrocele primarily affects premature babies. The hole between the scrotum and peritoneal cavity does not close on its own and fluid leaks out around the testicles. Hydrocele may eventually close on its own or may require surgical repair.

Hydrocephalus can be genetic or the result of an infection. The goal of treatment is to drain fluid from around the brain. Shunts may be placed in the brain to drain excess fluid. Hydrocephalus can be fatal if left untreated.

Hydranencephaly is a rare and fatal disorder in which an infant is born without a portion of its brain. Most babies die within a few days or weeks of birth. The cause of the condition is unknown.

Transillumination Procedure

Your doctor will dim the lights in the exam room to perform the transillumination test. A bright light is placed very close to the body part being examined, such as the breast, scrotum, head, or chest. The combination of lighted areas, dark spots, and colors that appear can help your doctor determine if further testing is needed.

Test Results

The area being tested will light up brightly if air, fluid, or non-solid masses such as cysts are present. The absence of an organ, such as a hemisphere of the brain, will allow light to pass through the skin and will appear bright. Solid masses will appear dark.

Your doctor will notify you of the results of the transillumination test. You will be scheduled for further testing if the results show any abnormalities.

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