What is an ultrasound scan?

An ultrasound scan creates a real-time picture of the inside of the body using sound waves. Ultrasound is generally painless and non-invasive. Ultrasound works differently to x-ray in that it does not use radiation.

During an ultrasound scans, a transducer directs high frequency sound waves are directed at the part of body being checked. The reflected sound waves (echoes) are sensed by the transducer and are used to create a picture on a monitor.

What are the types of ultrasound scans?

Common types of ultrasound scan include:

• abdominal ultrasound, which looks at s the internal organs of the abdomen, such as the liver, gallbladder, pancreas and spleen
• obstetric/pregnancy ultrasound, routinely used to assess the growth and health of unborn babies during pregnancy
• female pelvis ultrasound, used look at the female pelvis, uterus, cervix, fallopian tubes and ovaries, with a transvaginal (in the vagina) or abdominal transducer
• breast ultrasound, used to assess breast symptoms such as lumps, and also to screen for breast cancer in women with dense breast tissue
• renal ultrasound, used to scan the urinary tract, including the kidneys and bladder
• transrectal ultrasound, used to assess the prostate gland

Other types of ultrasounds include:

• Doppler ultrasound, which monitors blood flow in the major arteries and veins
• echocardiogram, which examines the heart
• 3D ultrasound, which shows a 3 dimensional picture of the inside of the body
• 4D ultrasound, which creates a 3 dimensional picture in motion

When is an ultrasound scan used?

Ultrasounds may be used for screening for or diagnose many conditions or to help with treatment.

Ultrasound scans can be used to:

• examine organs, such as the thyroid gland, the breast, the prostate and the liver
• examine muscles, tendons and ligaments to diagnose sprains, strains, trapped nerves and muscle tears
• examine lumps to see if they need further testing by distinguishing between fluid-filled cysts and solid lumps
• monitor blood flow, and identify blood clots, aneurysms (bulging arteries), narrowing of arteries and decreased blood flow
• help guide treatments, for example, by showing the correct site for an injection or to guide a biopsy needle to the correct place

Ultrasound has many uses in pregnancy. These include includes assessing gestational age, monitoring progress and screening for complications. Ultrasounds are commonly performed at 8 – 13 weeks and 18 – 20 weeks gestation — the first and second trimester scans. Additional ultrasound scans are usually only needed in certain situations. 3D and 4D ultrasound scans are sometimes offered in pregnancy for non-medical reasons. You should discuss having these scans with your obstetrician or GP.

Ultrasounds should only be performed when necessary. Speak to your doctor or specialist about whether an ultrasound is needed. For more information, visit the Choosing Wisely Australia website.

What are the limitations of ultrasound?

Ultrasound has a limited role in imaging bone or tissues that are full of air, such as the lungs. Ultrasound may not be as effective in people living with overweight or obesity, because the sound waves must pass through more fat to reach the target site.

How do I prepare for an ultrasound scan?

To prepare for an ultrasound scan:

• Bring your referral letter and any ultrasound scan or x-ray results you have received over the past 2 years, if they were performed at another location.
• Follow the instructions provided to you. You may need to fast, or to drink a lot of water and not go to the toilet before the procedure.
• Leave your jewellery and valuables at home.

If you have diabetes, it is important to tell the sonographer (ultrasound technician) before your ultrasound. If you have any questions or concerns, contact the imaging practice for advice.

How is an ultrasound scan performed?

An ultrasound scan is performed using a hand-held scanner (transducer) connected to a computer. High frequency sound waves are sent into the body. As the sound waves penetrate the tissue and spread, the echoes are converted to electrical impulses that show a picture on a screen.

During most ultrasound scans, you will be asked to lie on your back or side. Gel is applied to the skin. The sonographer will move the transducer on the gel. The sonographer may need to apply gentle pressure, but this usually does not cause any discomfort.

Ultrasounds during pregnancy are important for:

• checking the baby's development
• checking for multiple pregnancies
• picking up abnormalities

If you are having a transvaginal ultrasound scan, you will be asked to empty your bladder and undress from the waist down, with a gown or sheet to cover you. The transducer is slightly larger than a tampon. It will be covered in a protective sleeve or condom and lubricated with gel, inserted into the vagina and gently moved around.

You can request a female sonographer to perform transvaginal ultrasound, if you wish.

If you don't want to have a transvaginal ultrasound, or your sonographer doesn't consider it suitable (such as in children), you may be offered an external pelvic ultrasound instead.

Before having a transrectal ultrasound, you will need to have an enema. A narrow transducer, coated in gel, is inserted into the rectum, from where it can take images of the prostate and surrounding tissues. This can be uncomfortable but shouldn't hurt.

An ultrasound scan can take 20 – 60 minutes. It is an outpatient procedure (you will not be admitted to hospital), performed by a specially trained doctor, radiologist or sonographer. There are no aftereffects and you'll should be able to go about your normal activities afterwards.

Are there any risks with ultrasound?

Because it does not involve radiation, ultrasound is very safe and can be used routinely in pregnancy.

The sound waves produced during ultrasound are beyond the threshold of human hearing, so you won't hear them.

Resources and support

For more information about how and why ultrasounds are performed, see the Inside Radiology website.