An ultrasound is an imaging test that uses high-frequency sound waves to make pictures of organs and structures in the body. An ultrasound works by bouncing sound waves off different parts of the body.
Why an ultrasound is done
An ultrasound may be done to:
- look at the size, location and structure of soft tissue organs
- distinguish fluid-filled cysts from solid tumours
- guide the doctor during a needle aspiration, biopsy or some types of cancer treatment
- see how far cancer has spread (staging)
- show how fast and in which direction blood flows through vessels (a Doppler ultrasound)
How an ultrasound is done
An ultrasound is usually done as an outpatient procedure in a doctor’s office, clinic or hospital. This means that you don’t stay overnight. The test usually takes 15 to 30 minutes, but it may take longer.
Depending on the organ or structures being studied in an ultrasound, you may be told to:
- not eat or drink anything for several hours before the test
- take a laxative
- have an enema
- drink a large amount of water just before the test so that your bladder is full
For the test, you will lie on an ultrasound table. The ultrasound technologist puts a type of gel on the skin over the area to be examined. The gel lubricates the skin and improves transmission of the sound waves.
A microphone-like instrument, called a transducer, is placed directly on the skin and moved across the area being examined. For some types of ultrasound the transducer may be inserted into a body opening, such as the rectum (transrectal ultrasound) or the vagina (transvaginal ultrasound).
High-frequency sound waves from the transducer bounce off organs and tissues. A computer analyzes the echoes created by the sound waves and displays images on a screen.
You can usually return to your normal activities after the test.
There are no side effects with an ultrasound. This test shouldn’t be painful, but sometimes the pressure of the transducer on the body can be uncomfortable if it is placed on an area that is already sore.
What the results mean
An ultrasound cannot always tell the difference between a cancerous (malignant) tumour and a non-cancerous (benign) tumour.
The radiologist examines the pictures and prepares a report for your doctor. Your doctor will talk to you about the results and decide whether further tests, procedures, follow-up care or additional treatments are needed.
Special considerations for children
Preparing children before a test or procedure can help lower their anxiety, increase their cooperation and develop their coping skills. This includes explaining to children what will happen during the test, such as what they will see, feel and hear.
Preparing a child for an ultrasound depends on the age and experience of the child. Find out more about helping your child cope with tests and treatments.