Ultrasound scans are a common and safe imaging test used to look at the inside of your body. Whether you’re checking on a pregnancy or investigating a medical issue, proper preparation can help ensure the scan goes smoothly and produces clear images. In this guide, we’ll explain why ultrasounds are done, how to prepare for your ultrasound appointment, what to expect during the scan, and what happens afterwards. We’ll also answer frequently asked questions about ultrasound scans.

Prepare for an Ultrasound Scan

Why Are Ultrasound Scans Done?

Ultrasound scans (also called sonograms) use sound waves to create real time images of your organs and tissues. They are used in many situations because they are non invasive, painless, and do not use radiation. Here are some of the main reasons an ultrasound might be recommended:

  • Investigating symptoms or lumps: If you have unexplained pain, swelling, or a lump, an ultrasound can help identify the cause.

  • Monitoring known conditions: Doctors often use ultrasounds to keep an eye on existing health issues. For instance, checking thyroid nodules, liver disease progression, or the growth of fibroids in the uterus over time.

  • Guiding procedures: During certain medical procedures, ultrasounds help doctors with precision. They can guide a needle for a biopsy (taking a tissue sample) or ensure correct placement of an injection (such as a steroid injection into a joint).

  • Pregnancy scans: Ultrasound imaging is the standard way to monitor a baby's development in the womb. Throughout pregnancy, scans check the baby’s growth and health (for example, the 12 week dating scan or the 20 week anatomy scan). Ultrasounds can also confirm early pregnancy and check for multiple babies.

Ultrasound is often the first imaging test ordered because of its safety and effectiveness. From abdominal organs like the liver and kidneys to muscles, joints, and blood vessels (using a Doppler ultrasound to see blood flow), ultrasounds have a wide range of uses.

Types of Ultrasound Scans

  • External Ultrasound Scans

This is the most common type. A small handheld device called a probe (or transducer) is moved over the surface of your skin to capture images. The probe sends sound waves into the body and receives the echoes back, creating a picture on a screen. External ultrasounds are used for most scans, such as abdominal ultrasounds, pregnancy scans, scans of the neck (thyroid) or breast, and musculoskeletal ultrasounds of muscles or joints.

  • Internal Ultrasound Scans

In an internal ultrasound, the probe is inserted a short distance into the body for a closer look at certain internal organs. The two common internal scans are:

Transvaginal ultrasound: This is used to get detailed images of female pelvic organs like the uterus and ovaries. This is often done for early pregnancy scans or gynecological exams.

Transrectal ultrasound: This is typically used for imaging the prostate gland in men or examining the rectal area.

  • Endoscopic Ultrasound Scans

This is a more specialised type of ultrasound usually done in hospital settings. An endoscopic ultrasound involves a flexible tube (endoscope) with a probe at the end. The tube is gently inserted through your mouth and down into the oesophagus (food pipe) or stomach to image areas like the digestive tract, pancreas, or nearby lymph node

In addition to these main types, there are special ultrasound techniques such as Doppler ultrasound (to measure blood flow), echocardiograms (ultrasound of the heart), and 3D/4D ultrasounds (often used in pregnancy to see more detailed or moving images). But no matter the type, preparation is key to getting the best results from your scan.

How to Prepare for an Ultrasound Scan

Preparation for an ultrasound scan depends on the area of the body being examined. When your scan is booked, the hospital or clinic will usually provide instructions specific to your test.

  • Abdominal Ultrasound (Liver, Gallbladder, Pancreas, etc.): You may be asked to fast for 6 to 8 hours before an abdominal ultrasound. This means no eating and usually no drinking (other than small sips of water if needed for medications).

  • Pelvic Ultrasound (Womb, Ovaries, Bladder): You’ll be instructed to drink plenty of water beforehand and have a full bladder during the scan. A full bladder pushes the pelvic organs into view and acts as a "window" for the ultrasound to see the uterus and ovaries. Typically, you might be told to drink about 1–2 pints (approximately 500–1000 mL) of water an hour before your appointment and avoid urinating until after the initial scan.

  • Pregnancy Ultrasound: Preparation depends on how far along the pregnancy is. Early pregnancy scans (around 6–12 weeks) often require a full bladder for the best view. Later pregnancy scans (20 weeks and onward) usually do not require a full bladder since the baby and amniotic fluid provide a good window.

  • Transvaginal Ultrasound: If you are scheduled for an internal transvaginal scan (often done in addition to or instead of an external pelvic scan), you may be asked to arrive with an empty bladder. A full bladder can actually interfere with the view in a transvaginal scan.

  • Transrectal Ultrasound: For a prostate or rectal ultrasound, the clinic might advise you on bowel preparation. This could mean using a mild enema or laxative the day before to ensure your bowels are empty. A clear rectum makes it easier to get good images of the prostate.

  • Endoscopic Ultrasound: In these cases, you will typically need to fast (no food) for at least 6 hours before the procedure, similar to preparation for a gastroscopy. You might be allowed clear fluids up to 2 hours before. Because sedation is involved, you may also be instructed to arrange for someone to take you home afterwards.

What Happens During an Ultrasound Scan Appointment?

Knowing what to expect can help you feel more at ease during your ultrasound appointment. Ultrasound scans are typically quick (often 15–30 minutes) and painless. Here’s a step by step look at how an ultrasound scan usually unfolds:

Before the Scan Begins

When you arrive, you’ll be greeted by a sonographer or other healthcare professional who will perform the scan. They may confirm your identity and the type of ultrasound you’re having. Before you enter the scan room (or once you’re inside), you might be asked to do the following, depending on the area being scanned:

  • Change clothing: If necessary, you will be asked to undress to expose the area that needs scanning. You might change in a private cubicle or behind a curtain. For some scans, you can just adjust your clothing (for example, lowering a waistband or lifting a shirt) rather than fully undressing.

  • Position yourself: The sonographer will ask you to lie on an examination couch (a flat, padded table). They will position you depending on the scan. For a belly ultrasound, lying flat on your back is common. For a neck ultrasound, you might lie on your back with your chin tilted up. The room lights might be dimmed so the sonographer can see the ultrasound monitor clearly.

Getting Your Ultrasound Scan Results

One of the great advantages of ultrasound is that the images are available instantly. However, the way you receive your results can vary depending on the setting and the reason for the scan:

  • Immediate feedback: In some cases, the sonographer or doctor performing the ultrasound will discuss initial findings right there and then. This is more common in certain settings for example, during a pregnancy ultrasound, the sonographer might point out your baby’s heartbeat and organs as they go, or in an urgent situation, a radiologist might give an on the spot impression of what they see.

  • Formal report later: Often, especially in NHS hospitals, the person doing the scan (if they are a sonographer and not a doctor) will send the images to a radiologist or specialist doctor to analyse. The radiologist then writes a report which is sent to the doctor who referred you (such as your GP or specialist). This process can take a bit of time. Typically, ultrasound results are ready in a few days to a week.

  • If you don’t hear back: When you leave your ultrasound appointment, make sure you know what the next step is. If the sonographer didn’t explain results on the spot, it usually means a doctor will review them. You might have been told, “Your GP will have the report in 5 days” or something similar. If that time passes and you haven’t been contacted, it’s a good idea to call your GP’s surgery or the clinic to ask if the results are back.

It’s common that you’ll be given a printout or digital copy of an ultrasound image of the baby as a keepsake. For diagnostic scans (like checking an organ), you usually won’t get images to take home, but you can request a copy of your results from your doctor. Private Ultrasound clinics often provide a written report directly to you or very quickly to your doctor, and sometimes even give you the images on a CD or via a secure link.

Discussing the results: Once the results are ready, a doctor will explain what (if anything) the ultrasound found. If the scan was normal, that’s reassuring news and your doctor will guide you on next steps or other tests if needed.

Ultrasound Scan Safety and Side Effects

Ultrasound scans are one of the safest medical imaging tests available. They use sound waves, not ionising radiation, so there’s none of the radiation exposure you’d get from an X-ray or CT scan. Here’s what to know about safety and any possible side effects:

  • No proven harm from sound waves: The ultrasound waves used for medical scans have been used for decades without evidence of harm. They are high frequency sound waves that your ears cannot hear.

  • External scans are painless: An external ultrasound shouldn’t cause you any pain. The worst you might experience is a cool gel sensation and maybe slight pressure. If the area being scanned is already painful (for example, a tender ankle or a sore abdomen), pressing the probe there might cause discomfort.

  • Internal scan discomfort: A transvaginal or transrectal ultrasound might be a bit uncomfortable simply due to the nature of inserting the probe. You could feel pressure or a sensation of needing the loo in the case of a rectal scan. However, it should not be sharply painful. If you do feel pain, let the practitioner know right away.

  • Allergies or reactions: The ultrasound gel is typically hypoallergenic. It’s water soluble and easily wiped off. Allergic reactions to the gel are extremely uncommon. If you have sensitive skin or known allergies, you can mention it, but most people tolerate the gel without any issues

  • After the scan: There are generally no after effects from an ultrasound. You can eat, drink, and resume activities immediately (unless you had sedation for an endoscopic ultrasound, in that case, you’ll need to recover from the sedative as advised by the medical team).

Frequently Asked Questions about Ultrasound Scans

An ultrasound can check many parts of the body and diagnose a wide range of conditions because it creates real time images of soft tissues. It is commonly used to assess lumps or masses, helping to tell whether they are cysts or solid growths. It can evaluate internal organs such as the liver, kidneys, gallbladder and pelvic organs to investigate symptoms like abdominal or pelvic pain.

Ultrasound plays a key role in pregnancy, confirming and monitoring the baby’s development. Doppler ultrasound checks blood flow and can detect issues such as clots or narrowed arteries. Heart ultrasounds, called echocardiograms, assess how well the heart and its valves are working. Ultrasound is also used to guide medical procedures like biopsies.

In summary, only certain ultrasounds (mostly abdominal area scans) require an empty stomach. Always follow the instructions given by your healthcare provider. If you’re ever unsure whether you should fast or not, call the ultrasound department to double-check. It’s important because if you eat when you were supposed to fast, the scan might have to be rescheduled. Conversely, fasting when you don’t need to might just make you unnecessarily hungry and uncomfortable.

No, ultrasound scans are not painful. External scans involve a handheld probe moving over the skin, which may cause mild pressure but should not hurt. Internal scans like transvaginal or transrectal ultrasounds might feel slightly uncomfortable due to the insertion of the probe, but they should not be painful. If you experience discomfort, always let the sonographer know.

A repeat scan may be recommended if the initial images were unclear due to factors like bowel gas, insufficient bladder filling, or body positioning. In pregnancy, follow up scans might be used to monitor baby growth, placenta location, or fluid levels. Repeats are routine and do not indicate anything is necessarily wrong.

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