An ultrasound scan is one of the most widely used medical imaging tests for looking inside the body without using ionizing radiation. It uses high-frequency sound waves to create real-time images of organs, tissues, blood vessels, and, during pregnancy, the developing baby. Doctors may recommend an ultrasound to investigate symptoms, monitor an existing condition, assess blood flow, or guide certain medical procedures.
Because ultrasound can show movement as well as structure, it is useful for many different parts of the body. Depending on the area being examined, the scan may be performed over the skin or with a specialized probe placed inside a body cavity.
Understanding the different types of ultrasound, how to prepare, what happens during the examination, and how results are reported can make the process much easier.
What Is an Ultrasound Scan?
An ultrasound scan, also called sonography or diagnostic ultrasound, is an imaging examination that uses sound waves to produce pictures of structures inside the body.
During a typical examination, a small handheld device called a transducer is placed against the skin. The transducer sends high-frequency sound waves into the body and receives the echoes that return from different tissues. A computer processes those echoes and displays images on a monitor.
Unlike X-rays and CT scans, standard diagnostic ultrasound does not use ionizing radiation. It is also generally noninvasive and well tolerated.
Ultrasound can be used to examine structures such as:
- Liver and gallbladder
- Kidneys and bladder
- Pancreas and spleen
- Thyroid gland
- Heart and blood vessels
- Uterus and ovaries
- Testicles and scrotum
- Muscles, tendons, and joints
- Developing babies during pregnancy
- The brain and hips in infants
The exact information obtained depends on the type of ultrasound and the body area being examined.
How Does an Ultrasound Scan Work?
Ultrasound works through the reflection of sound waves.
The transducer sends pulses of high-frequency sound into the body. When these waves encounter different tissues, fluids, or organs, some of the energy is reflected back toward the transducer.
The machine analyzes these returning echoes and uses them to construct an image. Differences in tissue density and the way sound travels through the body help create the patterns seen on the screen.
The sonographer can watch the images in real time and capture specific views or measurements needed for the examination.
What Is the Ultrasound Gel For?
A clear, water-based gel is normally applied to the skin before the scan.
The gel removes air between the transducer and the skin because air can interfere with the transmission of ultrasound waves. It also allows the probe to move smoothly across the examination area.
The gel is generally easy to wipe away after the examination and normally does not stain clothing.
What Are the Main Types of Ultrasound?
There is no single ultrasound examination that is suitable for every situation. Different techniques are used depending on the body part, symptoms, and information the healthcare professional needs.
Abdominal Ultrasound
An abdominal ultrasound examines structures in the abdomen, including the liver, gallbladder, kidneys, pancreas, spleen, and abdominal blood vessels.
It may be requested when someone has abdominal pain, abnormal laboratory results, suspected gallstones or kidney stones, or other concerns involving abdominal organs.
Pelvic Ultrasound
A pelvic ultrasound examines organs such as the uterus, ovaries, cervix, and surrounding structures.
Depending on the clinical question, it may be performed through the abdomen or with an internal probe.
Transvaginal Ultrasound
A transvaginal ultrasound uses a specially covered probe inserted into the vagina to obtain detailed images of the pelvic organs.
It can be used to evaluate the uterus and ovaries and is also used in certain pregnancy-related examinations. The procedure may cause some pressure or discomfort, but patients should tell the healthcare professional if they experience pain.
Transrectal Ultrasound
A transrectal ultrasound uses a probe inserted into the rectum. It may be used to examine the prostate and nearby structures.
Because this is an internal examination, patients may experience pressure or temporary discomfort.
Breast Ultrasound
Breast ultrasound uses sound waves to examine breast tissue. It can help evaluate an area of concern and may also be used to guide certain procedures such as a needle biopsy.
It may be performed alongside other forms of breast imaging when additional information is needed.
Thyroid Ultrasound
A thyroid ultrasound examines the thyroid gland and surrounding neck structures.
It can show the size and appearance of the thyroid and help evaluate nodules or other structural abnormalities.
Musculoskeletal Ultrasound
Musculoskeletal ultrasound is used to examine structures such as muscles, tendons, ligaments, and joints.
One advantage is that images can be obtained while a body part is moving. This can provide information that is difficult to obtain from a static image.
Obstetric Ultrasound
Obstetric ultrasound is used during pregnancy to examine the developing fetus and assess pregnancy-related structures.
Ultrasound is widely used for pregnancy monitoring because it provides real-time images without ionizing radiation.
What Is Doppler Ultrasound?
Doppler ultrasound is a specialized ultrasound technique used to evaluate blood flow.
Moving blood cells change the frequency of reflected sound waves. The ultrasound system can process this information to show the direction and characteristics of blood flow.
Doppler techniques include color Doppler, power Doppler, and spectral Doppler. Depending on the examination, blood flow may be displayed as colors, graphs, or measurements.
Doppler ultrasound may help assess:
- Blood flow through arteries and veins
- Narrowing of blood vessels
- Possible blockages
- Blood flow to certain organs
- Abnormal vascular structures
It is also commonly incorporated into other ultrasound examinations when blood-flow information is important.
What Is 3D or 4D Ultrasound?
Traditional ultrasound generally produces two-dimensional images. Modern ultrasound systems can also process sound-wave data to create three-dimensional representations.
3D ultrasound creates a three-dimensional image of the scanned structures.
4D ultrasound adds movement over time to three-dimensional imaging, creating a moving 3D view.
These techniques may be useful in selected medical applications, but whether they are appropriate depends on the clinical purpose of the examination.
Why Is an Ultrasound Scan Done?
Doctors may recommend an ultrasound for many different reasons. It can help investigate symptoms, monitor known conditions, examine organs, evaluate blood flow, or guide procedures.
Common reasons include:
- Investigating unexplained pain
- Evaluating swelling or a lump
- Examining an organ that may be affected by disease
- Assessing blood flow
- Monitoring pregnancy
- Evaluating certain abnormalities
- Guiding a needle biopsy or fluid aspiration
- Monitoring a condition over time
Ultrasound is particularly useful for many soft-tissue structures that may not be clearly demonstrated by conventional X-rays.
An ultrasound does not automatically provide a final diagnosis. The images are interpreted together with symptoms, medical history, physical examination, laboratory results, and other tests when appropriate.
How to Prepare for an Ultrasound Scan
Preparation depends heavily on the type of ultrasound.
Some examinations require little or no preparation, while others may require fasting or a full bladder. The imaging center or healthcare professional should provide specific instructions for your appointment.
Common Preparation Instructions
Depending on the scan, you may be asked to:
- Wear loose, comfortable clothing.
- Remove jewelry or piercings near the examination area.
- Change into a medical gown.
- Avoid eating or drinking for a specified period.
- Drink water before the examination.
- Avoid urinating before a pelvic or bladder examination if instructed.
For some scans, patients may be asked not to eat or drink for several hours beforehand. For other examinations, drinking water and keeping the bladder full can improve the quality of the images.
Do not assume that fasting or drinking water is required for every ultrasound. Following the instructions provided for your specific examination is more important than following general advice found online.
What Happens During an Ultrasound Scan?
Most external ultrasound examinations are straightforward.
You will usually lie on an examination table, although your position may change depending on the area being examined. The sonographer applies gel to the skin and moves the transducer across the area of interest.
The sonographer may ask you to:
- Lie still
- Turn onto your side
- Hold your breath briefly
- Change position
- Relax a particular muscle
- Move a joint during a musculoskeletal examination
The transducer sends and receives sound waves while the ultrasound machine displays images on a monitor.
Most ultrasound examinations take around 30 minutes, although more extensive examinations can take longer.
Is an Ultrasound Scan Painful?
Most external ultrasound scans are painless.
You may feel pressure as the sonographer moves the transducer over your skin. If the area being examined is already painful or inflamed, that pressure can sometimes be uncomfortable.
Internal ultrasound examinations can produce more noticeable pressure or discomfort. Tell the healthcare professional if you are experiencing significant pain so the examination can be adjusted where possible.
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Ultrasound Scan Types at a Glance
| Ultrasound type | Main area or purpose | Common feature |
|---|---|---|
| Abdominal | Abdominal organs | Liver, gallbladder, kidneys and more |
| Pelvic | Pelvic organs | Uterus and ovaries |
| Transvaginal | Female pelvic structures | Internal probe |
| Transrectal | Prostate and nearby structures | Internal probe |
| Breast | Breast tissue | Evaluation of specific areas |
| Thyroid | Thyroid and neck | Gland and nodules |
| Musculoskeletal | Muscles, tendons and joints | Can assess movement |
| Doppler | Blood vessels and circulation | Evaluates blood flow |
| Obstetric | Pregnancy | Fetal and pregnancy assessment |
The exact purpose and technique depend on the clinical question and the area being examined.
What Can an Ultrasound Scan Show?
Ultrasound can provide information about the size, shape, position, and appearance of many structures.
Depending on the examination, it may help identify:
- Fluid-filled structures
- Changes in organ appearance
- Certain masses or nodules
- Gallstones
- Kidney stones
- Changes in blood flow
- Some signs of inflammation or infection
- Structural abnormalities
For example, an abdominal ultrasound can examine the liver, gallbladder, kidneys, pancreas, spleen, and abdominal aorta.
However, ultrasound has technical limitations. Sound waves do not travel well through air or gas, and bone blocks the transmission of ultrasound waves. Deeper structures can also be more difficult to image in some patients.
For these reasons, a normal or inconclusive ultrasound does not necessarily rule out every possible medical condition.
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How Are Ultrasound Results Interpreted?
After the images are obtained, they are reviewed by an appropriately trained healthcare professional, often a radiologist.
The radiologist analyzes the images and prepares a report for the clinician who requested the examination. The ordering healthcare professional then discusses the findings with the patient and explains what they mean in the context of symptoms and other medical information.
An ultrasound report may include sections such as:
- Type of examination
- Reason for the examination
- Findings
- Measurements
- Description of organs or tissues
- Impression or conclusion
- Recommendations for follow-up
Why the Report May Contain Medical Terms
Radiology reports are written for healthcare professionals, so they can contain terminology that is unfamiliar to patients.
Words such as “echogenicity,” “cystic,” “solid,” “vascularity,” or “unremarkable” have specific medical meanings and should be interpreted within the full report.
A single word or measurement should not normally be interpreted in isolation.
If the report recommends another examination, that does not automatically mean a serious condition has been found. Additional imaging may simply be needed to obtain more information or monitor a finding over time.
How Long Does It Take to Get Ultrasound Results?
The timing varies according to the healthcare facility, type of examination, and reason for the scan.
Some patients may receive information shortly after the examination, while in other situations the images must first be formally reviewed and a report sent to the referring clinician. The NHS notes that results can sometimes take weeks depending on the circumstances.
If you have not received your results within the timeframe provided by your healthcare provider, contact the relevant clinic or medical practice rather than assuming what the result means.
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Is Ultrasound Safe?
Standard diagnostic ultrasound does not use ionizing radiation.
Major medical imaging guidance describes diagnostic ultrasound as extremely safe, and standard diagnostic ultrasound has no known harmful effects in humans when used appropriately.
This is one reason ultrasound is particularly useful in situations where repeated imaging may be necessary and during pregnancy.
Nevertheless, ultrasound should be performed for an appropriate medical purpose and by trained professionals. The safety and suitability of specialized procedures can depend on the exact examination being performed.
What Are the Advantages of Ultrasound?
Ultrasound has several practical advantages compared with other imaging techniques.
No Ionizing Radiation
Standard ultrasound uses sound waves rather than X-rays or other forms of ionizing radiation.
Real-Time Imaging
The examiner can watch structures and movement as the scan takes place. This is particularly useful for certain musculoskeletal examinations and procedures.
Useful for Soft Tissues
Ultrasound can provide useful images of many soft-tissue structures that are not demonstrated as clearly by conventional X-rays.
Usually Noninvasive
Most ultrasound examinations require only a transducer and gel placed against the skin.
Can Guide Procedures
Ultrasound can be used to guide certain minimally invasive procedures, including needle biopsies and fluid aspiration.
What Are the Limitations of Ultrasound?
Although ultrasound is versatile, it is not the ideal imaging method for every part of the body.
Air and gas can interfere with sound waves, which can make some bowel or abdominal structures difficult to visualize. Bone also limits how deeply ultrasound can penetrate. The quality of an examination can vary depending on the body area and the amount of tissue the sound waves must pass through.
A doctor may therefore recommend another imaging test, such as an X-ray, CT, or MRI, when ultrasound cannot provide enough information.
The choice depends on the suspected condition, body area, clinical question, and information needed.
What Should You Do After an Ultrasound?
For most standard ultrasound examinations, there is no special recovery period.
After the scan, the gel can be wiped from the skin and normal activities can generally be resumed immediately.
If your examination involved a specific procedure, internal technique, sedation, or another intervention, follow the instructions provided by your healthcare team.
Most importantly, wait for the formal interpretation and discuss the findings with the clinician responsible for your care.
Frequently Asked Questions About Ultrasound Scans
Do I Need to Fast Before an Ultrasound?
Not always. Some examinations require fasting, while others may require you to drink water and keep your bladder full. Preparation depends on the specific scan, so follow the instructions from your healthcare provider or imaging center.
Can I Eat Before an Ultrasound?
It depends on the examination. Abdominal imaging may involve restrictions on eating or drinking, while many other ultrasound examinations do not require fasting.
How Long Does an Ultrasound Take?
Many ultrasound examinations take around 30 minutes, although some can take up to an hour or longer depending on their complexity.
Can an Ultrasound Detect Everything?
No. Ultrasound has important limitations, particularly with air-filled structures and areas blocked by bone. Your healthcare provider may recommend additional imaging if ultrasound cannot answer the clinical question.
Can Ultrasound Be Used During Pregnancy?
Yes. Ultrasound is widely used to monitor pregnancy and examine the developing fetus. It does not use ionizing radiation.
When Will I Receive My Results?
Timing varies. Some results may be discussed soon after the examination, while others are reviewed and reported later by the radiologist or another qualified professional.
Final Thoughts on Ultrasound Scans
An ultrasound scan is a versatile imaging test that uses sound waves to produce real-time images of many structures inside the body. It can be used to investigate symptoms, monitor medical conditions, evaluate blood flow, examine pregnancy, and guide certain procedures.
Preparation varies considerably between examinations, so patients should follow the instructions provided for their specific scan rather than relying on general preparation rules.
The ultrasound itself is usually quick and well tolerated, but the images are only one part of the diagnostic process. A qualified healthcare professional interprets the findings alongside symptoms, medical history, examination results, and other tests when necessary.
If your report contains unfamiliar terminology or recommends follow-up imaging, discussing it with the clinician who ordered the scan is the best way to understand what the findings mean for your individual situation.
Zak is a dedicated medical and career writer specializing in sonography, healthcare education, and professional development. Through SonographerSalary.com, he shares in-depth insights on sonographer salaries, education pathways, and career tips to help readers build successful futures in medical imaging. His content combines accuracy with practical, easy-to-understand guidance, empowering students and professionals to make confident, informed career decisions.