Preparation for an ultrasound that involves examining the spleen, pancreas, liver or gallbladder requires eating a fat-free meal the night before the test and fasting until the start of the exam, notes Healthline. Doctors usually allow people to drink water before an ultrasound and instruct them about the proper dosages of medications, if any.
To prepare for an ultrasound scan that focuses on the abdomen, doctors often advise people to avoid eating anything for eight to 12 hours before the test to avoid blockage of the sound waves, explains Healthline. This allows the ultrasound technician, known as a sonographer, to obtain clear pictures of the abdomen. Before taking an ultrasound, a person should inform his doctor if he is taking prescription or over-the-counter medications and herbal supplements.
An ultrasound scan takes live pictures of the internal organs, vessels and tissues of the body using high-frequency sound waves, states Healthline. The sonographer rubs a lubricating jelly on the skin, and then presses an ultrasound transducer that transmits high-frequency sound waves that reflect the body's organs or bones and sends echoes into a computer.
An ultrasound scan poses no risks because it does not use radiation, according to Healthline. Doctors mostly use this test to view a developing fetus in a pregnant woman. They also order the test to diagnose symptoms such as pain and swelling.