Why Do I Need A Full Bladder For My Ultrasound Scan?

Picture of Sophia McCarthy

Sophia McCarthy

Operations Manager

If you’ve ever had a pregnancy ultrasound, you may have been told by the sonographer that you need to have a full bladder for the appointment.

But why do you need a full bladder when it’s the uterus that’s being scanned? It’s actually a question that we get a lot in our clinics, so let’s get into it!

How Ultrasound Works

Ultrasound was first used by a man called Karl Dussik in 1942 when he used it to try and detect brain tumours in the human skull. An adaptation of ultrasound was also being used by submarines in the navy which is more commonly known now as sonar.

Ultrasound works by emitting high frequency sound waves through the human body, and when they hit an object, they bounce right back; providing us with an image. These waves travel at different speeds throughout the body—and, like a submarine—work best in water.

This is also the reason why sonographers use gel between your skin and probe when conducting the scan. Ultrasound waves travel much easier through water and fluids than they do through gas and other objects.

 

Your Bladder Works As A Window

A full bladder allows ultrasound waves to travel through deep into your pelvic region which makes it easier to scan the uterus or other pelvic organs.  

Gas

One of the other reasons why you need a full bladder is to prevent your pelvic region being full of gas during the scan. Ultrasound waves don’t travel well through gas which means they won’t be able to produce a clean image of your internal organs. Unfortunately the only way to combat this gas is to ensure the person receiving the ultrasound has a full bladder.  

Conclusion

Now that you know the importance of having a full bladder for an ultrasound, be sure to come prepared for your scan to avoid the disappointment of a suboptimal pictures, or having to wait while your bladder fills up to get the best results possible. In some cases, if your bladder isn’t full enough you may be asked to come back another day and to try again. Not every scan requires a full bladder.

The following scans require a full bladder:

  • Pregnancy scans under 14 weeks
  • Pelvic scans (also known as gynaecological, uterus or ovary scans)
  • Urinary tract (also known as renal, kidney or bladder scans)

Once you are over 14 weeks pregnant, we no longer require you to have a full bladder as the uterus is big enough for us to see everything clearly.  

To more information about our first trimester pregnancy ultrasounds, click HERE. If you have any questions, please don’t hesitate to get in touch via our social media or via email. Our clinic phone numbers are also displayed at the top of the page!

 

 

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