Neonatal Ultrasound of the Urinary Tract

Abstract

Ultrasound has proven to be a safe and accurate diagnostic tool. In very simplified terms, ultra high frequency sound waves in the range of 3.5 to 7.0 megahertz are focussed into the area to be studied. Sound waves are reflected to varying degrees as the beam passes through structures of different densities. For example, in solid tissue, as the sound beam interacts with different types of tissue of a variety of densities, some of the beam is reflected back to the transducer, which serves both as transmitter and receiver. The structure appears echogenic on the displaying oscilloscope. If, however, a mass were particularly uniform in cell type, the sound beam would pass in a relatively uninterrupted manner from the front of the structure to the back. Few waves (echoes) would be reflected and the structure would appear relatively sonolucent (echo-free). Lymphomatous masses sometimes have this appearance. In the case of fluid-filled structures with no solid particulate matter (for example a cyst), no sound waves are reflected between those coming from the front and back walls of the cystic structure. The cyst is completely echo-free.