What is a Bladder Scanner and How to Use One

If you are unfamiliar with what a bladder scanner is and how to use one, hopefully this page will clear things up for you. Although it may seem complicated at first, it is actually quite simple.

What and when?  Supplies  Step by step  Download and print bladder scanner instructions (pdf)

What is It and When Should It be Used?

So what is it exactly and what is it used for? It is an ultrasound machine that uses sound waves to scan a patient's bladder to determine how much urine they have inside. This is typically done if there is suspicion that they are retaining urine which can cause serious issues such as a urinary tract infection (UTI) or even bladder rupture if not treated.

Note that just because they are urinating, that doesn't necessarily mean they aren't retaining. Retaining simply means they aren't completely emptying out their bladder. To see if this is the case, the patient is scanned immediately after they urinate. This is called checking their post void residual. This is one reason why it is important to keep up with their intake and output (I&O).

After a patient has had their foley catheter removed, they need to urinate within a certain amount of time. At the hospital where I am employed, that time frame is 8 hours. If they still haven't gone by then, we encourage them to go and if they are unable to, we bladder scan them. If they are retaining, there is usually an order to reinsert of the catheter or performing a straight cath.

How much urine in the bladder is considered too much? We typically have separate parameters ordered for each individual. They usually range between 250 and 350 mL (cc), but it really depends on the patient. Of course generally speaking, the larger the patient, the larger the bladder.


All of the supplies you need are as follows:

  • The bladder scanner machine with the probe attached
  • A bottle of ultrasound gel
  • A wipe that is safe for human skin
  • A sanitary wipe to clean the machine
Bladder scanner machineBladder scanner machine
Bladder scanner probeBladder scanner probe
Bladder scanner gelBladder scanner gel

Step by Step Instructions

  1. First, make sure the bladder scanner is in working condition and the battery is charged enough to perform a scan.
  2. Check and double check to make sure it is on the correct setting. There are typically three of them which include male, female, and child. Use child if they are less than 48 in (122 cm) tall and weigh less than 60 lbs (27 kg). Note that if the patient is female but has had a hysterectomy done in the past, use the male option.
  3. Make sure the patient is lying completely or nearly flat on a bed or exam table. Then expose their lower abdomen and pubic area. Be sure to keep privacy in mind.
  4. Warn them that the ultrasound gel may be a little cool on their skin and squeeze the bottle until there is at least a quarter sized amount, or about 1 in (3 cm) in diameter, of gel slightly above their pubic bone. This area is between their belly button and genitals. A little too much gel is better than not enough.
  5. Grab the probe which is typically shaped like a bar code scanner or a microphone. It has a wire that is attached to the machine at one end, and a rounded off part at the other end. Place the rounded end onto the gel and slightly move it around the area so the gel is distributed evenly.
  6. Push and hold the scan button until you hear a beep. You should see a circle of urine on the monitor. If the urine is not centered on the screen, move the probe slightly and scan again. The scanner I'm familiar with will even point you in the direction where you need to move the probe. Tilting it down towards their tailbone may also help get a clearer reading.
  7. Keep moving the probe and scanning until the urine is centered on the screen. This should give you the most accurate reading, which also typically ends up being the largest amount of urine scanned. Many machines also give you the option to save or print the end result.
  8. Afterwards, don't forget to wipe off the gel on the patient's abdomen with a wipe that is safe for human skin. Then use a sanitary wipe to clean off the probe before putting it away.

Medical References for Caregivers

List of Caregiver Supplies and Equipment

From What is a Bladder Scanner and How to Use One to Home

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