An ultrasound scan, sometimes called a sonogram, is a procedure that uses high-frequency sound waves to create an image of part of the inside of the body. An ultrasound scan can be used to monitor an unborn baby, diagnose a condition, or guide a surgeon during certain procedures.

Ultrasound is safe and painless. Ultrasound imaging, also called ultrasound scanning or sonography, involves the use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds that bounce back and a computer then uses those sound waves to create an image. Ultrasound examinations do not use ionizing radiation (as used in x-rays), thus there is no radiation exposure to the patient. Because ultrasound images are captured in real-time, they can show the structure and movement of the body's internal organs, as well as blood flowing through blood vessels. Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions.

How ultrasound scans work:
A small device called an ultrasound probe is used, which gives off high-frequency sound waves. You can't hear these sound waves, but when they bounce off different parts of the body, they create "echoes" that are picked up by the probe and turned into a moving image. This image is displayed on a monitor while the scan is carried out.

Preparing for an ultrasound scan:
Before having some types of ultrasound scan, you may be asked to follow certain instructions to help improve the quality of the images produced. For example, you may be advised to:
  • Drink water and not go to the toilet until after the scan – this may be needed before a scan of your unborn baby or your pelvic area.
  • Avoid eating for several hours before the scan – this may be needed before a scan of your digestive system, including the liver and gallbladder.

What happens during an ultrasound scan:
Most ultrasound scans last between 15 and 45 minutes. There are different kinds of ultrasound scans, depending on which part of the body is being scanned and why. The three main types are:
  • External ultrasound scan – the probe is moved over the skin
  • Internal ultrasound scan – the probe is inserted into the body
  • Endoscopic ultrasound scan – the probe is attached to a long, thin, flexible tube and passed further into the body.

After an ultrasound scan:
In most cases, there are no after-effects and you can go home soon after the scan is finished. If a sedative wasn't used, you can drive, eat, drink and return to your other normal activities straight away. External and internal ultrasound scans don't have any side effects and are generally painless, although you may experience some discomfort as the probe is pressed over your skin or inserted into your body. Endoscopic ultrasounds can be a bit more uncomfortable and they can cause temporary side effects, such as a sore throat or bloating. There's also a small risk of more serious complications, such as internal bleeding.

Are there any risks or side effects?
There are no known risks from the sound waves used in an ultrasound scan. Unlike some other scans, such as computerised tomography (CT) scans, ultrasound scans don't involve exposure to radiation.