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An ultrasound scan is a medical test that uses high-frequency sound waves to capture live images from the inside of your body. It’s also known as sonography.
The technology is similar to that used by sonar and radar, which help the military detect planes and ships. An ultrasound allows your doctor to see problems with organs, vessels, and tissues without needing to make 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:
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 eight to 12 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.
An ultrasound carries minimal risks. Unlike X-rays or CT scans, ultrasounds use no radiation. For this reason, they are the preferred method for examining a developing fetus during pregnancy.
Before the exam, you will change into a hospital gown. You will most likely be lying down on a table with a section of your body exposed for the test.
An ultrasound technician, called a sonographer, will apply a special lubricating jelly to your skin. This prevents friction so they can rub the ultrasound transducer on your skin. The transducer has a similar appearance to a microphone. The jelly also helps transmit the sound waves.
The transducer sends high-frequency sound waves through your body. 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. They form a picture that can be interpreted by the doctor.
Depending on the area being examined, you may need to change positions so the technician can have better access.
After the procedure, the gel will be cleaned off of your skin. The whole procedure typically lasts less than 30 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.
Written by: Brian Krans
Medically reviewed on: May 05, 2016: University of Illinois-Chicago, College of Medicine
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