An ultrasound test [also referred to as "sonography"] is a diagnostic medical imaging technique, which is performed to view a patients internal organs and to assess his or her blood flow through various vessels. An ultrasound is also performed on a pregnant lady so an obstetrician can check on the developing baby.

The technique uses high-frequency sound waves to produce images of the organs and structures of the body. Ultrasound scanners consist of a computer, a video display screen and a transducer probe that is used to scan the body. The transducer is a small hand-held apparatus attached to the scanner. The physician spreads a lubricating gel on the area being examined and then presses the transducer against the skin to obtain images. The sound waves that are sent by the transducer through the body are mirrored by the internal structures as ""echoes."" The echo patterns are then recorded and displayed as real-time visual images.

Ultrasound scanning is a method of examining the body's internal organs, including the heart, liver, gallbladder, spleen, pancreas, kidneys and bladder. It helps determine the source of pain, swelling or infection. Since the images are captured in real time, they demonstrate movement of internal tissues and organs, and allow physicians to observe the patients blood flow and heart valve functions. This helps to diagnose damage after a heart attack or other illness. Gallstones are easily spotted, as are kidney stones. Ultrasound identifies fluid, cysts, tumours or abscess in the abdomen or liver, and impaired blood flow from clots or arteriosclerosis in the legs can be detected. They are also used to evaluate superficial structures such as the thyroid gland and scrotum.

Due to its non-invasive and painless nature, the real-time imaging makes ultrasound scanning a good tool for guiding minimally invasive procedures and a useful diagnostic instrument in Obstetrics.