Most clinics recommend drinking 32 ounces (about 1 liter) of water one to two hours before a pelvic ultrasound, then holding your urine throughout the procedure. A full bladder pushes bowels aside and provides an acoustic window through which sound waves can better visualize pelvic organs like the uterus, ovaries, and prostate. The exact volume may vary—your ultrasound facility will provide specific pre-appointment instructions, as requirements differ based on equipment, operator preference, and the specific structures being examined. You'll typically be instructed not to empty your bladder after drinking until the scan is complete. If you drink too much, you may experience discomfort; if you drink too little, the images may be unclear and the procedure might need to be repeated. Some facilities ask you to arrive with a comfortably full bladder rather than specifying an exact amount. For transabdominal ultrasounds (the probe on your skin), bladder filling is usually critical. For transvaginal ultrasounds (the probe inserted into the vagina), less bladder filling may be needed since the probe sits closer to the organs being examined. Always follow the pre-appointment instructions sent by your specific clinic, as protocols can vary. If you're uncertain about how much to drink, contact the ultrasound facility directly rather than guessing—they can provide precise guidance for your appointment.