An ultrasound scan is a medical test that uses high-frequency sound waves to capture live images from the inside of your body. An ultrasound test allows your doctor to see problems with organs, vessels, and tissues without making an incision.
Unlike other imaging techniques, ultrasound uses no radiation. For this reason, it’s the preferred method for viewing a developing fetus during pregnancy.

Most people associate ultrasound scans with pregnancy. These scans can provide an expectant mother with the first view of her unborn child. However, the test has many other uses.
Your doctor may order an ultrasound if you’re having pain, swelling, or other symptoms that require an internal view of your organs. An ultrasound can provide a view of the:

• bladder
• eyes
• gallbladder
• kidneys
• liver
• ovaries
• pancreas
• spleen
• thyroid
• breast
• testicles
• uterus
• blood vessels

An ultrasound is also a helpful way to guide surgeons’ movements during certain medical procedures, such as biopsies.

The steps you will take to prepare for an ultrasound will depend on the area or organ that is being examined.
Your doctor may tell you to fast for 6 hours before your ultrasound, especially if your abdomen is being examined. Undigested food can block the sound waves, making it difficult for the technician to get a clear picture.
For an examination of the gallbladder, liver, pancreas, or spleen, you may be told to eat a fat-free meal the evening before your test and then to fast until the procedure. However, you can continue to drink water and take any medications as instructed. For other examinations, you may be asked to drink a lot of water and to hold your urine so that your bladder is full and better visualized.

Be sure to tell your doctor about any prescription drugs, over-the-counter medications, or herbal supplements that you take before the exam.
It’s important to follow your doctor’s instructions and ask any questions you may have before the procedure.

You will be lying down on a table with a section of your body exposed for the test.
The radiologist will apply a special lubricating gel to your skin. This prevents friction so they can rub the ultrasound transducer on your skin, and helps sound waves pass through the abdomen more efficiently by removing small pockets of air that may interfere. The gel is water-based and easy to clean off after the procedure. The transducer has a similar appearance to a microphone. The gel also helps transmit the sound waves.
The transducer device sends high-frequency sound waves into the body and picks up the responding signal. The waves echo as they hit a dense object, such as an organ or bone. Those echoes are then reflected back into a computer. The sound waves are at too high of a pitch for the human ear to hear. It is possible to create images by analyzing the data that these signals create. They form a picture that can be interpreted by the doctor. It is possible to display the ultrasound image immediately and to take photographs for future examination.
Depending on the area being examined, you may need to change positions so the technician can have better access.
In some cases, it may be necessary to use a Doppler ultrasound. This type of ultrasound can detect changes in blood flow.
After the procedure, the gel will be cleaned off of your skin. The whole procedure typically lasts less than 20 minutes, depending on the area being examined. You will be free to go about your normal activities after the procedure has finished.

Following the exam, your doctor will review the images and check for any abnormalities. They will call you to discuss the findings, or to schedule a follow-up appointment. Should anything abnormal turn up on the ultrasound, you may need to undergo other diagnostic techniques, such as a CT scan, MRI, or a biopsy sample of tissue depending on the area examined. If your doctor is able to make a diagnosis of your condition based on your ultrasound, they may begin your treatment immediately.