What is an ultrasound scan?

Ultrasound scanning, or sonography, is a type of imaging technique used to diagnose various conditions, guide certain procedures, or to examine fetal development during pregnancy. Unlike CT scans which use radiation, or MRI scans which use magnetic and radio waves, diagnostic ultrasound uses sound waves or echos to create images of the structures in your body. It is a non-invasive, safe, and painless procedure.

When might you need an ultrasound scan?

You would most probably have heard of a pregnancy ultrasound — used to produce images of the baby in the womb in order to examine the baby’s growth, position, any abnormalities, or to find out if you are having a baby boy or a girl.

However, an ultrasound scan has many different uses. Your doctor may use an ultrasound scan to visualise your internal organs, such as the liver and kidneys, pancreas, bladder, uterus, ovaries or testicles, as well as blood vessels.

Hence an ultrasound scan can help to:

  • Monitor the health of a developing baby
  • Examine if a lump is cancerous or just a fluid-filled cyst
  • Diagnose problems or inflammation in soft tissues, muscles, tendons, and joints
  • Evaluate blood flow and diagnose circulatory problems 
  • Detect and diagnose problems in the gallbladder, bladder, genitals, and prostate
  • Guide a needle for anesthetic injections or cancer treatment
  • Guide procedures such as a biopsy or endovascular procedures

How to prepare for an ultrasound scan?

Most ultrasound scans do not require any preparation before the procedure. Your doctor may advise you on the dietary restrictions to follow before the procedure, depending on the area or organ that is being examined.

Inform your doctor if you are on any medication, prescription drugs, or have any known allergies.

What happens during an ultrasound scan?

Before the procedure, you may need to wear a hospital gown and remove any metal objects or jewelry. You will most likely lie on your back on an examination table.

After you are well-positioned on the table, a radiologist or a sonographer will apply a clear, warm gel onto your skin over the area of your body to be examined. This gel lubricates your skin and helps to transmit sound waves by removing air pockets. This gel is safe and harmless and can easily be wiped off after the ultrasound scan.

Your radiologist then presses a transducer, a small hand-held device shaped like a microphone, against your skin and moves it back and forth until the desired images are captured. The transducer transmits high-frequency sound waves (that are inaudible to us) into your body. These sound waves are reflected back as echoes when they hit the internal organs, tissues, or blood vessels, and are then captured and sent back to the computer, which creates the images.

An ultrasound scan is usually painless and may present minimal discomfort. It typically takes around 30 minutes to an hour to complete.

What to expect after your ultrasound scan?

In most cases, you will be able to return to your normal activities immediately after your ultrasound scan. When the scan is completed, the images are sent to a radiologist for examination. Your doctor will follow-up with you on the results after a few days or a week.

Are there any risks involved in ultrasound scans?

Generally, ultrasound is a safe procedure that does not involve the use of harmful ionising radiation. There are no known risks associated with ultrasound scans. However, to minimise any unknown long-term risks, scans are only recommended when needed.

Although it is a powerful diagnostic tool, ultrasound has its limitations. Since ultrasound waves do not travel well through air or bone, ultrasound cannot be used to image the lungs, head, or the internal structures of bones. Different imaging techniques can be used, such as CT or MRI scans.