You will usually be required to abstain from eating or drinking for approximately 6 hours prior to the procedure. This reduces the amount of bowel gas and causes the gallbladder to distend.
If the main area of interest is the pelvis or urinary tract, however, you will be asked to attend with a full bladder. In this case you will be required to drink water prior to the examination. The full bladder displaces bowel loops out of the pelvis and provides a window through which the pelvic structures and prostate may be examined.
The ultrasound probe will then be moved smoothly and painlessly over the skin surface. Depending on the clinical circumstances, an examination may last from 5 to 20 minutes.