Ultrasound

Written by Brian Krans
Medically Reviewed by George Krucik, MD

What Is an Ultrasound?

An ultrasound scan is a medical test that uses high-frequency sound waves to capture live images from the inside of your body.

The technology is similar to that used by sonar and radar, which help the military detect planes and ships. An ultrasound allows your doctor to see problems with organs, vessels, and tissues—without needing to make an incision.

Unlike other imaging techniques, ultrasound uses no radiation, so it is the preferred method for viewing a developing fetus during pregnancy.

Ultrasound is also known as sonography.

Why an Ultrasound Is Performed

Most people associate ultrasound scans with pregnancy. These scans can provide an expectant mother with the first view of her unborn child. However, the test has many other uses.

According to the Radiological Society of North America, your doctor may order an ultrasound if you are experiencing pain, swelling, or other symptoms that require an internal view of your organs (RSNA, 2012). An ultrasound can provide a view of the:

  • bladder
  • brain (in infants)
  • eyes
  • gallbladder
  • kidneys
  • liver
  • ovaries
  • pancreas
  • spleen
  • thyroid
  • testicles
  • uterus
  • blood vessels

An ultrasound is also a helpful way to guide surgeons’ movements during certain medical procedures, such as biopsies.

How to Prepare for an Ultrasound

The steps you will take to prepare for an ultrasound will depend on the area or organ that is being examined.

Your doctor may tell you to fast for eight to 12 hours before your ultrasound, especially if your abdomen is being examined. Undigested food can block the sound waves, making it difficult for the technician to get a clear picture.

For an examination of the gallbladder, liver, pancreas, or spleen, you may be told to eat a fat-free meal the evening before your test and then to fast until the procedure. However, you can continue to drink water and take any medications as instructed.

Be sure to tell your doctor about any prescription drugs, over-the-counter medications, and herbal supplements that you take before the exam.

It is important to follow your doctor’s instructions and ask any questions you may have prior to the procedure.

An ultrasound carries no risks. Unlike X-rays or CT scans, ultrasounds use no radiation. For this reason, they are the preferred method for examining a developing fetus during pregnancy.

How an Ultrasound Is Performed

Before the exam, you will change into a hospital gown. You will most likely be lying down on a table with a section of your body exposed for the test.

An ultrasound technician, called a sonographer, will apply a special lubricating jelly to your skin. This prevents friction so he or she can rub the ultrasound transducer—similar in appearance to a microphone—on your skin. The jelly also helps transmit the sound waves.

The transducer sends high-frequency sound waves through your body. The waves echo as they hit a dense object, such as an organ or bone. Those echoes are then reflected back into a computer. The sound waves are at too high of a pitch for the human ear to hear.

Depending on the area being examined, you may need to change positions so the technician can have better access.

After the procedure, the gel will be cleaned off your abdomen. The whole procedure typically lasts less than 30 minutes. Following it, you will be free to go about your day and normal activities.

After an Ultrasound

Following the exam, your doctor will review the images and check for any abnormalities. He or she will call you to discuss the findings, or to schedule a follow-up appointment. Should anything abnormal turn up on the ultrasound, you may need to undergo other diagnostic techniques, such as a CT scan, MRI, or a biopsy sample of tissue. If your doctor is able to make a diagnosis of your condition based on your ultrasound, he or she may begin your treatment immediately.

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