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What is ultrasound?

Ultrasound imaging is a medical test that helps doctors diagnose and treat illness. It is also called ultrasound scanning or sonography. Ultrasound uses high-frequency sound waves to see the inside of the body. An ultrasound technologist uses a small probe called a transducer and a special ultrasound gel on the outside of the body to see an image of the inside of the body.

Unlike X-rays, ultrasound does not use radiation. Because ultrasound images are seen as they are actually happening, they can show the structure and movement of the body’s internal organs, as well as blood flowing through blood vessels. Ultrasound is safe and painless.

A Doppler ultrasound study may be a part of an ultrasound exam. Doppler ultrasound is a technique that shows how blood flows through a blood vessel, including the body’s major arteries and veins in the abdomen, arms, legs, and neck. It can help the doctor see:

  • Objects blocking blood flow, such as clots,
  • Blood vessels becoming more narrow, and
  • Tumors and defects in the blood vessels and vascular system.

Ultrasound helps diagnose a variety of conditions, including:

  • Pain or swelling in the abdomen,
  • Problems with how the liver is working,
  • Swollen organs in the abdomen, and
  • Stones in the gallbladder or kidney.

Ultrasound may also be used to get more information for biopsies.

How should my child get ready for an ultrasound?

Your child should wear comfortable, loose-fitting clothing for the ultrasound exam. Some clothing or jewelry may need to be taken off in the area of the body that will be examined. Your child may be asked to wear a gown during the exam.

How your child prepares for the exam will depend on the type of ultrasound to be done.

  • For an ultrasound of the liver, gallbladder, spleen, and pancreas, your child may be asked to eat a fat-free meal on the evening before the test, and then not eat for 6 to 8 hours before the test.
  • For ultrasound of the kidneys and bladder, your child may be asked to drink up to 64 ounces of liquid 2 to 3 hours before the test to fill the bladder. The best liquid to drink is water. It might be hard to get a small child to drink 64 ounces, but the goal is to get your child to drink as much as possible.

How is an ultrasound done?

For most ultrasound exams, your child will lie face up on an exam table.

A clear water-based gel is put on the area of the body being studied. This gel helps the transducer make better contact with the skin. The gel might feel cold at first, and when the ultrasound is over, it will be wiped off.

Next, the technologist presses the transducer firmly against your child’s skin on the spot that is supposed to be examined. To get the best image, the technologist may sweep the transducer across the spot or may press more firmly in one spot. Doppler ultrasound is done the same way.

Some ultrasound images are called contrast studies. To do this kind of test, the radiologist injects contrast liquid (a type of dye) into a vein. If your child does not already have a vein open with an IV or other port, then the nurse might need to start an IV in the ultrasound area. If an IV is needed, the staff will talk to you before it is done.

When the exam is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed.

Who reads the results and how do I get them?

A radiologist, a doctor trained to supervise and read radiology exams, will look carefully at the images. Then that doctor will send a signed report to your primary care doctor or other staff member who sent your child for the exam. The doctor who sent your child for the exam will share the results with you and your child. In some rare cases, the radiologist may talk about the results with you at the end of your child’s exam.

Follow-up exams may be needed, and your doctor will explain the reason why. Sometimes a follow-up exam is done because there is a question about what has been found, and it needs to be seen from more angles or with a special imaging technique. A follow-up exam may also be needed so that any change in an area that is not normal (called an abnormality) can be watched over time. Follow-up exams are sometimes the best way to see if treatment is working or if an abnormality is stable over time.

What are the benefits and risks?


  • Ultrasound is extremely safe and does not use any ionizing radiation.
  • Ultrasound gives a clear picture of soft tissues that do not show up well on X-ray images.
  • Most ultrasound scanning is not invasive (does not go inside the body) and does not use needles or injections.
  • Sometimes, an ultrasound exam may be uncomfortable for a short time, but it is almost never painful.


  • For standard diagnostic ultrasound, there are NO known harmful effects.


If you have questions about ultrasound tests, please talk to your child’s doctor, nurse, or an ultrasound technologist.

This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

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