What is an ultrasound examination?

Ultrasound is a widely used technique which produces detailed images of the body.

Ultrasound uses high frequency sound waves (much higher than human ears can hear) which are produced by the ultrasound probe (transducer). The reflected sound waves are detected by the probe and used to create an image which is displayed on the television screen of the ultrasound machine.

The sound energy used is absorbed by the body as heat but there is no noticeable warming effect. There are no known harmful effects.

It can be used to gain information about a variety of conditions, including pregnancy, gallstones and varicose veins. An ultrasound which shows blood flow may also be called Colour Flow Doppler or Duplex Scan.


Depending on the area to be scanned, you may have to follow some special instructions about the amount of food and fluids you consume prior to your scan. You may be asked to fast or to drink some water.

Upper abdominal scans (including the liver, gall bladder and pancreas) require you to fast for 6 hours beforehand.

If you have diabetes, please inform your referring doctor who will advise you of any special dietary instructions.

If you have diabetes and are on insulin, or suffer epilepsy, please discuss the timing of your scan with our booking staff.

Scans of the kidneys, bladder and, in men, the prostate gland require a full bladder and you will be asked to drink 1 litre of water 1 hour before. If you feel you are ‘bursting’ before your appointment, please try to only partly empty your bladder. A full bladder is not needed for examination of the scrotum and testes in men.

There is no preparation required for Musculoskeletal or Vascular (Doppler) ultrasound scans.

Please take your normal medication with a sip of water.


You may be asked to change into a gown, but you will be covered during your examination except for the area required to be examined. You may be asked to lie on a table for the ultrasound examination.

A layer of warmed gel will be spread over the area to be examined to facilitate good contact as this helps to produce the best possible images. The ultrasound transducer is then placed over the area to be investigated.

Ultrasound examinations are not painful and are generally not invasive. However, some examinations may be uncomfortable depending on the type of procedure required and the preparation for this, e.g. a full bladder, may be uncomfortable.

Scans of the shoulder or other joints may require your cooperation in performing special movements while scanning is performed.

Colour Doppler ultrasound uses a special technology to look at blood flowing in arteries and veins. This is most commonly used to study the carotid arteries in the neck (supplying the brain) and veins in the legs.

During these studies you will often hear strange noises as signals from flowing blood is transformed into sound. We may need to gently squeeze the calf a few times when examining the leg veins.

How long will the procedure take?

Scanning may take up to 1 hour but generally most appointments are for 30 minutes. Often the radiologist will come to speak with you and view the screen. This is quite routine and should not cause alarm.

Films are produced from the television images and are interpreted by the radiologist. The results will then be forwarded to your doctor.

Please bring any previous x-rays with you on the day of your examination.