Ultrasound involves the use of high-frequency sound waves to create images of organs and systems within the body.

An ultrasound machine creates images that allow various organs in the body to be examined. The machine sends out high-frequency sound waves, which reflect off body structures. A computer receives these reflected waves and uses them to create a picture. Unlike with an x-ray or CT scan, there is no ionizing radiation exposure with this test.

The test is done in the ultrasound or radiology department. You will be lying down for the procedure. A clear, water-based conducting gel is applied to the skin over the area being examined to help with the transmission of the sound waves. A handheld probe called a transducer is moved over the area being examined. You may be asked to change position so that other areas can be examined.

For specific information about ultrasound examinations, please refer to the following topics:

• Abdominal ultrasound
• Breast ultrasound
• Doppler ultrasound of an arm or a leg
• Doppler/ultrasound of the heart (echocardiogram)
• Duplex ultrasound
• Pregnancy ultrasound
• Testicle ultrasound
• Thyroid ultrasound
• Transvaginal ultrasound
• Vascular ultrasound

Preparation for the procedure will depend on the body region being examined.

There is generally little discomfort with ultrasound procedures. The conducting gel may feel slightly cold and wet.

The reason for the examination will depend on your symptoms.

Results are considered normal if the organs and structures in the region being examined are normal in appearance.

The significance of abnormal results will depend on the body region being examined and the nature of the problem. Consult your health care provider with any questions and concerns.

There are no documented risks. No ionizing radiation exposure is involved.

Most ultrasound examinations are performed in the manner described. However, certain circumstances require that the ultrasound probe be inserted into the body, rather than simply passing it over the skin. Consult your health care provider to determine the specifics of your test.

Cosgrove DO, Meire HB, Lim A, Eckersley RJ. Ultrasound: general principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 4th ed. New York, NY: Churchill Livingstone; 2001:chap 3.