Ultrasound Scan: What to Expect

How does ultrasound work?

An ultrasound machine uses a device called a transducer or probe.

The probe sends high-frequency sound waves into the body. Different tissues reflect these waves in different ways. The returning signals are processed by the ultrasound machine to create images on a screen.

Because ultrasound images are produced in real time, the person performing the examination can:

• —move the probe around
• —examine structures from different angles
• —watch organs move
• —assess blood flow
• —ask you to change position
• —apply gentle pressure to investigate particular areas.

Ultrasound is therefore a particularly interactive form of medical imaging.

Why might I need an ultrasound?

Ultrasound may be used to investigate:

• —abdominal pain
• —pelvic pain
• —abnormal liver blood tests
• —gallstones
• —kidney problems
• —urinary symptoms
• —abnormal vaginal bleeding
• —suspected ovarian or uterine conditions
• —testicular symptoms
• —thyroid lumps
• —soft-tissue lumps
• —tendon or muscle injuries
• —blood-vessel problems.

It can also guide procedures such as injections, drainage procedures and biopsies.

Who performs the ultrasound?

Your examination may be performed by a sonographer, a radiologist, or another appropriately trained healthcare professional.

A sonographer is a healthcare professional specifically trained in performing and interpreting ultrasound examinations. A radiologist is a doctor specialising in medical imaging.

Who performs and reports your scan varies between hospitals and according to the type of examination.

How long does an ultrasound take?

Many ultrasound examinations take approximately 10–45 minutes, although some examinations take longer.^[1]

The duration depends on:

• —the body part being examined
• —the clinical question
• —how easy the structures are to visualise
• —whether multiple areas need assessment
• —whether Doppler imaging is required
• —whether an internal scan is also performed.

A longer examination does not necessarily mean that something abnormal has been found.

Do I need to prepare?

Possibly.

This is one of the biggest differences between types of ultrasound. You might be asked to:

• —fast before the scan
• —drink water beforehand
• —arrive with a full bladder
• —avoid emptying your bladder
• —remove jewellery from the area
• —wear loose-fitting clothing.

Your appointment letter should explain what preparation is required.

Why might I need to fast?

For some abdominal ultrasound scans, hospitals ask patients not to eat for several hours beforehand.

This can improve assessment of structures such as the gallbladder, liver, pancreas and upper abdomen. Eating can cause the gallbladder to contract and can increase bowel gas, which may make certain structures more difficult to examine.

For example, some NHS departments request approximately 6 hours of fasting before an abdominal ultrasound. But protocols vary.

Follow your own department's instructions rather than applying a standard fasting period yourself.

Why might I need a full bladder?

A full bladder can act as an acoustic window during a pelvic ultrasound. It helps move bowel loops out of the way and can improve visualisation of structures within the pelvis.

For a pelvic ultrasound, you may therefore be asked to drink water before your appointment and avoid going to the toilet. Different hospitals specify different amounts of fluid — commonly somewhere around 500 mL to 1 litre.

Again: follow the exact instructions on your appointment letter. If your bladder is not sufficiently full, you may occasionally be asked to drink more water and wait before the examination.

What happens during an external ultrasound?

Most ultrasound examinations are external.

You will usually:

• —Lie or sit on an examination couch.
• —Move clothing away from the area being examined.
• —Have ultrasound gel placed on your skin.
• —Have the ultrasound probe moved across the area.
• —Be asked to change position if necessary.
• —Occasionally be asked to hold your breath.

The room may be dimmed so the healthcare professional can see the ultrasound screen more clearly. The probe may need to be pressed relatively firmly against the skin to obtain good images.

Why is gel used?

Air interferes with ultrasound waves.

The gel removes the layer of air that would otherwise sit between the ultrasound probe and your skin. This allows the sound waves to pass efficiently into the body.

The gel is harmless and can simply be wiped off afterwards.

Does ultrasound hurt?

Usually not.

An external ultrasound should generally be painless. You may feel:

• —pressure from the probe
• —mild discomfort if the area is already painful
• —temporary discomfort from having a very full bladder.

For example, pressing over an inflamed gallbladder, a tender joint, an abdominal mass or an already painful pelvis can sometimes be uncomfortable.

Tell the person performing the scan if you are in pain.

What is a pelvic ultrasound?

A pelvic ultrasound commonly assesses structures such as the uterus, endometrium, ovaries, bladder and other pelvic structures.

In many patients, a gynaecological pelvic ultrasound may involve two parts:

Transabdominal ultrasound

The probe is moved across the lower abdomen, usually while the bladder is full.

Transvaginal ultrasound

A specially designed ultrasound probe is gently inserted into the vagina to obtain closer, more detailed views of the pelvic organs.

Not everyone requires both.

Why might I be offered a transvaginal ultrasound?

A transvaginal scan places the probe closer to the uterus, ovaries, cervix and surrounding pelvic structures.

This often provides more detailed images than scanning through the abdominal wall alone. It can be particularly useful when investigating:

• —pelvic pain
• —abnormal bleeding
• —ovarian cysts
• —fibroids
• —suspected endometriosis
• —early pregnancy
• —other gynaecological symptoms.

What happens during a transvaginal ultrasound?

You will usually be asked to empty your bladder first.

You will be given privacy to undress from the waist down and will usually lie on the examination couch with your knees bent.

A specially designed ultrasound probe is cleaned, covered with a protective sheath, lubricated with gel, and gently inserted into the vagina. Only a relatively small part of the probe needs to enter the vagina.

The operator then carefully moves the probe to obtain images of different pelvic structures.

Can I refuse an internal ultrasound?

Yes.

A transvaginal ultrasound requires your consent. The examination should be explained to you before it is performed. You are in control and can ask for the examination to stop at any point.^[1]

If you do not feel comfortable having a transvaginal ultrasound, tell the healthcare professional. They can explain why it has been recommended, what information it may provide, and what alternatives are available.

Can I have someone in the room?

You can ask about having a chaperone present. Depending on local policy, this may be a member of staff, and in some situations someone accompanying you.

If this is important to you, mention it when you arrive.

Can I have a pelvic ultrasound during my period?

In many circumstances, yes.

Being on your period does not automatically prevent a pelvic or transvaginal ultrasound. Certain examinations are actually timed to a particular stage of the menstrual cycle.

Follow any specific advice from the department performing your scan.

What is Doppler ultrasound?

Doppler ultrasound assesses movement of blood. It can help examine blood flow within arteries, veins, organs, masses, testes, ovaries and other tissues.

You may see areas of colour appear on the ultrasound screen. This does not mean something abnormal has necessarily been found. Colour Doppler is simply one of the tools used to demonstrate blood flow.

Can ultrasound see everything?

No.

Every imaging test has strengths and limitations. Ultrasound is extremely useful because it produces real-time images, does not use ionising radiation, can assess movement, can assess blood flow, is relatively accessible, and can guide procedures.

But ultrasound can be limited by factors including:

• —bowel gas
• —body habitus
• —the depth of a structure
• —bone
• —air-filled lungs
• —the position of the organ being examined.

Sometimes another test such as CT, MRI or X-ray is required to answer the clinical question.

Does a normal ultrasound mean nothing is wrong?

Not necessarily.

A normal ultrasound means that no abnormality visible on that particular ultrasound examination has been identified. It does not exclude every possible medical condition.

For example, some forms of endometriosis, bowel disease, early inflammatory disease, or small or difficult-to-visualise abnormalities may not be reliably demonstrated on routine ultrasound.

The meaning of a normal scan therefore depends on what symptoms you have, what the scan was looking for, and how the examination was performed.

Is ultrasound safe?

Diagnostic ultrasound has been used medically for decades. It does not expose patients to ionising radiation.^[1,2]

Ultrasound equipment does deposit acoustic energy into tissues, so healthcare professionals follow established safety principles and use the amount of ultrasound exposure required to obtain diagnostic information.^[2] This is especially relevant for specialised applications and pregnancy imaging.

For ordinary clinically indicated diagnostic ultrasound, it is regarded as a very safe imaging technique.

Does ultrasound cause cancer?

There is no ionising radiation exposure from diagnostic ultrasound. This makes ultrasound fundamentally different from investigations such as X-ray and CT.

Current clinical ultrasound safety practice focuses on using ultrasound appropriately and minimising unnecessary acoustic exposure while obtaining the required diagnostic information.^[2]

Can I have ultrasound if I am pregnant?

Yes.

Ultrasound is used extensively throughout pregnancy.

If you are having an ultrasound for a reason unrelated to pregnancy, tell your healthcare team if you know or think you may be pregnant so that they have the complete clinical context.

What happens after the scan?

For most routine ultrasound examinations you can wipe away the gel, get dressed, leave immediately, and eat and drink normally afterwards.

If you have had an ultrasound-guided procedure rather than a diagnostic scan alone, different aftercare instructions may apply.

Will the person doing the scan tell me the result?

Sometimes — but not always.

This varies between hospitals, examinations, professional roles and clinical circumstances.

You may occasionally be given an explanation at the end of the examination. In other situations, the images are reviewed and a formal report is sent to the clinician who requested the scan.

The NHS advises that ultrasound results may be available at the appointment or may take a few weeks, depending on the reason for the examination and local arrangements.^[1]

Why is the person scanning me sometimes quiet?

Silence does not mean that something bad has been found.

Ultrasound requires significant concentration. The person performing the examination is simultaneously positioning the probe, interpreting moving images, changing machine settings, taking measurements, comparing structures, recording representative images and documenting findings.

Try not to interpret facial expressions, pauses or silence during your examination.

Research suggests that patients can have misunderstandings about ultrasound, including expectations about the examination and how results are communicated.^[3]

What if they spend longer on one area?

This also does not necessarily mean something is wrong.

Some areas simply take longer to visualise, require several measurements, are technically difficult to assess, need Doppler evaluation, or need comparison with the opposite side.

The duration of a scan should not be used to predict your result.

What should I bring?

Usually you only need:

• —your appointment information
• —any information requested by the hospital
• —your usual medications unless you have been instructed otherwise.

Wear comfortable clothing that allows easy access to the body part being examined.

Five things to remember

• —Ultrasound does not use ionising radiation.
• —Preparation varies — follow your own appointment instructions.
• —Some abdominal scans require fasting.
• —Some pelvic scans require a full bladder and may include a transvaginal scan.
• —Do not try to judge your result from how long the scan takes or how quiet the operator is.

Feeling anxious about your scan?

Anxiety around medical imaging is common.

Studies examining diagnostic imaging have found that clear information and educational material can improve patient experience and may reduce pre-procedure anxiety.^[4,5]

If you are worried about any part of your ultrasound — particularly an internal examination — tell the healthcare professional before the scan begins. Questions are welcome.