Ultrasound (US) is an additional cross-sectional diagnostic imaging tool allows for the evaluation of organs without the superimposition inherent in radiography. Sound waves are emitted from a transducer and travel through organs and tissues, generating echoes that are detected by the equipment and then are converted to gray scale images. Using Doppler techniques, blood flow through vessels, organs, and diseased tissues can be evaluated. Ultrasound also allows for targeted sampling of small amounts of body cavity fluid as well as fine-needle aspirates and biopsies of abnormal organs and tissues.

Radiography and US are complementary imaging modalities. While radiography provides limited information about the internal architecture of abdominal organs, it provides invaluable information about the entire abdominal cavity, including bones and areas such as the pelvic canal that cannot be adequately evaluated with US. It is important that these imaging modalities are used in conjunction with one another to provide the best possible diagnostic accuracy and patient care.