What does an ultrasound scan mean, and what is it used for?

Ultrasound is a painless, gentle and safe imaging method that lets the doctor examine internal organs, soft tissues and blood vessels in real time. It does not use ionising radiation, so it can be repeated when needed.

How does ultrasound work?

The scanner emits high-frequency sound waves that the human ear cannot hear. These waves enter the body and bounce back to different degrees from different tissues and organs. The probe detects the returning waves, and the machine turns them into an image on the monitor. Because the picture is live, not only structure but, in some cases, movement and blood flow can be seen.

Which organs can be examined?

Ultrasound can assess many organs and body regions. The type of scan always depends on the complaints and the medical recommendation.

Abdominal and pelvic ultrasound – among other structures, the liver, gallbladder and bile ducts, pancreas, spleen, kidneys, bladder, abdominal aorta and other abdominal findings can be examined. Size, shape and structure can be assessed, and cysts, stones, focal lesions, signs of inflammation or abnormal fluid collections may be recognised.

Thyroid ultrasound – size and structure, possible enlargement, nodules or cysts, and nearby lymph nodes can be assessed. Ultrasound shows structural changes: laboratory tests are usually also needed to judge thyroid function.

Soft-tissue ultrasound – subcutaneous and other superficial findings can be examined. It may be used as part of investigating palpable lumps, swellings, cysts, inflammatory changes or enlarged lymph nodes.

What is Doppler ultrasound?

Doppler ultrasound is a special technique that gives information on the direction and speed of blood flowing in arteries and veins. The doctor can see whether flow is adequate, and whether there is narrowing or a finding that suggests blockage.

Neck vessel Doppler – vessel walls, diameter, possible calcification or plaque, the degree of narrowing, and the direction and speed of flow can be assessed. Significant narrowing of the neck arteries can raise the risk of cerebral circulation problems and stroke.

Leg veins – Doppler ultrasound can help detect deep-vein thrombosis. Vein patency can be checked, and reduced flow caused by a clot can be shown.

Leg arteries – arterial Doppler is used for narrowing, blockage and other flow problems. It may be warranted, for example, with pain on walking, a cold limb, a wound that heals poorly, or suspected reduced circulation in the legs.

How does the scan take place, and how should you prepare?

The patient usually lies on their back. The doctor exposes the area to be examined and applies a water-based gel so that no air remains between the probe and the skin. The probe is moved gently over the surface. The scan is mostly painless, though light pressure on a tender or inflamed area can cause brief discomfort. It usually takes 15–30 minutes.

Preparation depends on the type of scan:

• before an abdominal scan you may need to avoid eating for several hours
• an abdominal or pelvic scan may require a full bladder
• thyroid, soft-tissue and most vascular scans usually need no special preparation

Always follow the doctor’s or clinic’s instructions about regular medicines. Ask the clinic in advance for the exact requirements.

Is ultrasound painful or dangerous?

Standard ultrasound through the skin is not invasive, does not use X-rays, and has no known harmful effect when used appropriately. It is usually painless, and you can return to usual activities straight afterwards.

Although ultrasound helps detect many changes, not every organ or disease can be assessed with full accuracy. Air-filled organs and areas hidden by bone are harder to evaluate. Body habitus, bowel gas and preparation also affect the result. If a finding needs clearer definition, the doctor may recommend further laboratory or imaging tests, such as CT or MRI.

When is emergency care needed?

Sudden one-sided swelling, pain, warmth or colour change in a leg needs prompt medical review. Seek emergency care immediately if:

• shortness of breath develops
• chest pain occurs
• blood-stained sputum appears
• there is a rapid, major deterioration

Booking an appointment at a private clinic does not replace emergency care.

Frequently asked questions

Do I need a referral for ultrasound?

It depends on whether the scan is in public or private care. In private practice an appointment can usually be booked without a referral, but it is still worth discussing with a doctor whether ultrasound is needed and which type.

How long does ultrasound take?

Most scans take about 15–30 minutes. Duration depends on the region examined and the findings.

Do I get the result immediately?

The doctor reviews the images during the scan. You usually receive a written report, which should be discussed with the treating doctor if needed.

Can ultrasound be repeated?

Yes. Because it does not use ionising radiation, it can be repeated when there is a medical reason.

Does ultrasound detect cancer?

Ultrasound can find focal lesions and organ changes that need further investigation, but on its own it is not always enough to confirm or exclude cancer.

The information here is for guidance only. It does not replace a medical examination, diagnosis or a personalised treatment recommendation.