Also known as sonography or diagnostic medical sonography

Key points about ultrasound

  • An ultrasound uses high frequency sound waves to create pictures of parts of the inside of your body.
  • You cannot hear the sound waves emitted by a probe that is moved around the part of your body being scanned.
  • Ultrasound scans are sometimes called sonograms. They don't use use radiation and so they are very safe.
  • As a scan is done, the pictures are sometimes projected onto a screen to create a moving image. A good example of this is the scanning done during pregnancy that can show images of your unborn baby as it moves in your womb.
Technician does right wrist ultrasound on man
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Ultrasound scans can be used to diagnose conditions, to assess the size and function of one of your body parts (eg, your heart) and to assess and monitor your baby before it is born. They can also be used to guide a doctor or other health professional as they carry out some procedures or surgeries.

Common areas that can be scanned are your: 

  • abdomen (tummy/puku)
  • breast
  • kidneys 
  • liver
  • pelvis – in women this commonly checks your ovaries, bladder and uterus wall thickness, in men it can be used to check your prostate, bladder and testicles
  • heart – this is done by an ultrasound scan known as an echocardiogram or ECHO
  • arteries and veins – this is done by an ultrasound scan called a Doppler
  • uterus and baby during pregnancy
  • joints – ultrasound of joints can be used to assess fluid in your joint and also check for arthritis.

Ultrasound scans are often used in real time by health professionals doing procedures. Examples of this may be to guide the taking of a breast biopsy (sample of breast tissue) accurately, the positioning of tubes in people undergoing hospital based treatments, or the correct positioning of a needle when fluid is being injected into, or taken out of a joint.

There are 3 main types of ultrasound scans:

  • External scan – the ultrasound probe is moved over the skin on the outside of your body. This is the most common type of ultrasound scan.
  • Internal scan – the probe is inserted into your vagina or rectum to get a better view of nearby parts.
  • Endoscopic scan – the probe is attached to a tube and passed further into the body to examine deeper parts of your body.

An ultrasound is often quicker, safer and easier to do than more intensive tests such as CT scans. Often an ultrasound will be enough for your doctor to make a diagnosis and plan any next steps or treatments. Some family doctors now have ultrasound machines in their practice to do external scans.  

This will depend on what sort of scan you're having.

External scan

An external scan will take approximately 20 minutes and you will be fully awake through the scan. For most scans you do not need to do any preparation before coming to the hospital, radiology or GP service. If you are having a bladder, kidney or early pregnancy ultrasound, you may need to drink 1 or 2 large glasses of water and not go to the toilet. This helps fill your bladder and makes it easier to see certain areas.

For an external scan you will usually be asked to lie down on an examination couch on your side or back. A warm gel is used to improve conduction through the skin by the probe (a small hand held instrument) and to help the probe to glide over the skin as it is moved over the area. By changing the angle and position of the probe, the sonographer (ultrasound technician) or radiologist (medical doctor specialising in imaging) is able to get clearer pictures of the soft tissues inside your body.

Internal scan

These scans are usually done through the vagina or the rectum. A very small lubricated probe is passed gently into the vagina or the rectum for the scan to be done. These scans can cause some discomfort, but they don’t take long and they provide excellent pictures of parts of the body such as the prostate or parts of the womb (uterus) and ovaries.

Endoscope scan

Your preparation for this scan will be guided by the department doing the scan. Usually you will be asked not to eat or drink anything from midnight the night before, and you may need to take a liquid laxative and liquid diet the day before. It is important that you discuss any medicines that you are taking with the scanning team before the day when you are preparing for the scan. Because you may not be eating on the day before your scan some of your medicines might need to be changed. 

On the day of the scan you will usually be given a sedative to help you relax. The scan is done by passing an endoscope, or flexible tube, through your mouth and into your stomach and bowel. This type of scan is uncomfortable, but you will be well supported by the staff performing the scan. Having an ultrasound scan by endoscopy is the same as having an endoscopy. Endoscope scans are very useful tools to enable accurate diagnosis and treatment of a range of internal issues such as cysts, cancers and tumours. Read more about endoscopy.

An endoscope scan will usually take around 3045 minutes. Once it is done you will be cared for in a recovery room until you are fully awake. You will be ready to go home around 4 hours after the scan. Make sure you have someone to drive you home and that you are able to rest for the rest of the day. Usually, you can eat and drink within 1–2 hours of having the scan. 

If you have had any ultrasounds before and have the films at home, bring these with you. It can be helpful for the radiologist to compare findings with previous results. If you are having an endoscope scan bring all the medicines that you usually take to the appointment.

If you are having an external or internal scan you can get back to normal activities straight away. If you are having an endoscope scan allow for a day of rest on the day of the scan. A report will be sent to your doctor or hospital clinic and you can arrange a follow up appointment to discuss the results.

Endoscopic ultrasound(external link) Waitemata Endoscopy, NZ 
Ultrasound(external link) Mayo Clinic Health System, US
Radiology services(external link) Auckland Radiology Group, NZ
Ultrasound – tests and procedures(external link) Mayo Foundation for Medical Education and Research, US


  1. Ultrasound scan(external link) NHS, UK, 2021
  2. Endoscopic ultrasound(external link) Waitemata Endoscopy, NZ 
  3. Ultrasound(external link) Mayo Clinic, US

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