This post is all about preparing your patient for a “formal” ultrasound. You know, the kind you order and that are generally performed by an ultrasonographer as opposed to by you at the bedside. I’ll cover NPO and bladder filling specifically. Note that these may not be exactly what you do at your institution – so check your local protocols.

No specific prep (NPO or bladder) needed for the following ultrasounds

  • FAST
  • Scrotum/testicles
  • Appendix only
  • Intussusception
  • Joint effusion (hip, ankle etc,.)
  • Superficial lesions, lymph nodes, skin and soft tissue (abscess)
  • Deep venous thrombosis
  • Fractures
  • Cerebral ventricles in a neonate

General abdominal ultrasound

Liver, pancreas, spleen etc,. – You know, the organs of the abdomen

  • Birth to 2 years: NPO 4 hours
  • 2-8 years old: NPO 6 hours
  • 8+ years old: NPO 8 hours

The NPO time helps reduce the amount of fluid/air in the bowels and can help with resolving the solid organs.


Unless performing a transvaginal ultrasound a full bladder serves as an acoustic window for the transabdominal ultrasound to better image the ovaries and uterus. A “full bladder” is generally one in which the patient says that they really have to pee! You can also check the volume at the bedside before sending them over. In order to fill the bladder you can do one of the following:

  • Make the patient drink – this could take a while, at least 1-1-.5 hours if they have an empty bladder.
    • Under 5 years old: 8-12 ounces 1 hour prior to the ultrasound
    • 5-12 years: 12-16 ounces 1 hour prior to the ultrasound
    • 12-18 years: 18-24 ounces 1.5 hours prior to the ultrasound
  • Insert a Foley catheter after which the bladder can be filled with warm water or saline and the ultrasound performed immediately
  • Insert an IV and give isotonic fluids. In general it takes 1.5 to 2 hours or more to fill the bladder, especially if the patient is dehydrated. You may be able to speed this up by using the push-pull technique or a device like the Belmont Rapid infuser


A full bladder is needed for assessing the entire urinary tract. Without one you can’t adequate assess for ureteral jets in stone evaluation for instance.

  • Patients can drink prior to the ultrasound
    • 1-3 years 4 to 6 ounces 30 minutes prior to the ultrasound
    • 3-6 years: 8 to 12 ounces 1 hour prior to the ultrasound
    • 6-12 years: 12-16 ounces 1 hour prior to the ultrasound
    • 12+ years: 16-18 ounces 1 hour prior to the ultrasound
  • IV bolus – Similar to the Pelvic Ultrasound, this usually takes 1-2 hours


NPO for 3 hours