How Ultrasound Works

Ultrasound is energy in the form of sound waves. The most common type of ultrasound is called two-dimensional (2D) ultrasound. In this type of ultrasound, a device called a transducer sends waves through the body. The sound waves comes into contact with tissues, body fluids, and bones. The waves then bounce back, like echoes. The transducer receives these echoes, which are turned into images. The images can be viewed as pictures on a video screen.

An ultrasound exam may be done in a health care professional's office, hospital, or outpatient radiology facility. It may be performed by your obstetrician-gynecologist (OB-GYN), a radiologist, or a specially trained technician.

How an Ultrasound Exam is Done

During a pelvic ultrasound exam, an ultrasound transducer is either moved across your abdomen (transabdominal ultrasound) or placed in your vagina (transvaginal ultrasound). The type of ultrasound exam you will have will depend on what types of images are needed and why the exam is being done.

Transabdominal Ultrasound

If you having a transabdominal ultrasound exam, wear loose-fitting clothes. This will allow your abdomen to be exposed easily. You may need to drink several glasses of water during the 2 hours before your exam. This will make your bladder full. A full bladder is helpful because it creates a "window" through which structures underneath it or around it can be seen more clearly.

For this exam, you will lie on a table with your abdomen exposed from the lower part of the ribs to the hips. A gel is applied to the surface of the abdomen. This improves contact of the transducer with the skin surface. The handheld transducer then is moved along the abdomen to make images.

Transvaginal Ultrasound

For a transvaginal ultrasound exam, you will be asked to change into a hospital gown or undress from the waist down. It is recommended that you empty your bladder before the test. You will lie on your back with your feet in stirrups, like you would for a pelvic exam. The transducer for this exam is shaped like a wand. It is covered with a sheath, similar to a condom, and is lubricated before it is inserted into the vagina.