Sonography, or ultrasound scanning, is a non-invasive diagnostic method which is exceptionally useful in gaining a picture of the inside of soft tissues. The image is made by tracking different reflections and absorptions of ultrasound waves by various types of tissue. For example, ultrasound waves are poorly reflected (but well absorbed) by tissue containing a lot of fluid, i.e. hypoechoic masses. The tissue masses that reflect ultrasound waves are described as hyperechoic.

Ultrasound scanning is used to examine the digestive system, urinary tract, liver, adrenal glands, prostate, testes, ovaries and the uterus, abdominal lymph nodes, heart, as well as small masses such as swellings, tendons and lymph nodes, and to determine pregnancy. Sonography can also be used to guide fine-needle aspirations of tumors, examine changes in the organs and perform cystocenthesis.