Why Do You Need to Drink Water Before a Pelvic Sonogram?

Patients who are scheduled for a pelvic sonogram are asked to drink water prior to the exam. The standard protocol is to drink 32 ounces of water one hour before the exam. There are several reasons why a full bladder is necessary for obtaining good ultrasound images of the pelvic organs, which are the uterus and ovaries.

Sonographic Window

• The sonographer uses a camera that transmits and receives sound waves, called a transducer, to look at the pelvic organs through the bladder to obtain good images. When this is done, the bladder is called a sonographic window.

Bowel

• Ultrasound cannot be used to see through bowel gas. Filling the bladder pushes bowel out of the way so the pelvic organs can be seen.

Image Clarity

• Fluid can intensify the sound waves to produce a clearer image. Imaging through a full bladder contributes to better ultrasound images of the pelvic organs.

Landmark

• A full bladder serves as a landmark for finding the pelvic organs. The uterus is located behind the filled bladder and the ovaries are typically located at each side.

Organ Position

• A filled bladder can flatten out the uterus so it can be easily viewed in a lengthwise position. The filled bladder may also push the ovaries into a better position for visualization.