Ultrasound or sonography is a medical imaging technique which uses high frequency sound waves  and their echoes instead of radiation. It is a safe, fast and reliable technique for imaging many areas of the body including  pregnancy, abdominal and pelvic disorders, and vascular flow.

There are some preparations required in ultrasound. For abdominal scanning you may be asked to refrain from eating or drinking the day of your exam. For pregnancy or pelvic exams a full bladder is required.

We are often asked why a full bladder is necessary. It is due to the physics of sound waves. Sound waves need a medium through which to travel. Fluid is one of the best carriers of sound waves. 

Sound waves are emitted from a transducer. This is the probe that the technologist gently  guides over the body part being scanned.  The waves must travel to the organs inside the body, and when the sound wave reaches the organ an echo occurs. The transducer must then hear and record the echo.  The full bladder facilitates the sound wave travel. In the abdomen, the liver which is highly vascular provides the path

The conducting gel is non-staining but may feel slightly cool and wet. There is no sensation at all from the ultrasound waves.