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Preparing for a Bladder Ultrasound: What You Need to Know

by David Smith

| Updated October 1, 2023 |
Thanks to recent advances in technology, bladder scans have replaced catheterization as the preferred method to monitor and assess various aspects of bladder function.

Now instead of medical professionals having to perform a difficult and risky invasive procedure like a catheterization, they can get the information they need with a simple non-invasive bladder scan.

With a bladder ultrasound, the wall of your bladder and the pouches within it, which are called diverticula, are shown in real-time. With these pictures, bladder ultrasounds can tell doctors a lot, such as if there are problems with the size or width of the walls of the bladder.

The images from a bladder scanner can also help doctors identify urinary tract infections, bladder stones, cysts and tumors in the bladder, a buildup of fluids, and how much urine a bladder can hold.

In this article, we are going to take a closer look at bladder scans, including why they are most commonly performed and what you can do to prepare for an upcoming bladder scan to ensure the procedure goes well.

1.What Are the Most Common Reasons Bladder Scans Are Performed?

A bladder scan is performed for several important reasons with some of the most common being:

Urinary Retention Assessment

One of the primary reasons for performing a bladder scan is to assess whether a person is retaining urine in their bladder after they have attempted to urinate. Urinary retention can occur due to various medical conditions, such as an enlarged prostate in men, neurological disorders, bladder dysfunction, or urinary tract obstructions. The scan helps determine if a significant amount of urine remains in the bladder after urination.

Post-Operative Monitoring

After certain surgical procedures, especially those involving the lower abdomen or pelvis, healthcare providers may use bladder scans to monitor post-operative urinary retention. This is important to prevent complications and discomfort in the immediate post-surgical period.

Urinary Incontinence Assessment

Bladder scans can assist in the evaluation of urinary incontinence, a condition where an individual involuntarily leaks urine. By measuring post-void residual (PVR) volume, healthcare providers can determine if incomplete bladder emptying contributes to incontinence and devise appropriate treatment plans.

Monitoring Bladder Health

In some cases, regular bladder scans may be performed to monitor changes in bladder volume over time. This can be helpful in tracking the progression of certain medical conditions, such as neurogenic bladder dysfunction or chronic urinary tract infections.

Assessment of Bladder Function

Bladder scans can provide valuable information about the overall function of the bladder, including its ability to contract and relax properly. This information can aid in the diagnosis and management of bladder disorders.

Guidance for Catheterization

Bladder scans are often used to determine if catheterization is necessary. If the scan reveals a significant post-void residual volume, catheterization may be recommended to empty the bladder completely.

Monitoring Fluid Balance

In certain healthcare settings, such as intensive care units (ICUs), bladder scans may be used to monitor fluid balance in critically ill patients. Accurate measurements of urine output are crucial for assessing a patient's condition.

Overall, a bladder scanner is a valuable tool that helps healthcare providers diagnose and manage a variety of urological conditions, optimize patient care, and ensure proper bladder function. The specific reason for performing a bladder scan will depend on the individual patient's medical history, symptoms, and the healthcare provider's clinical judgment.

2.What Happens During a Bladder Scan?

Bladder ultrasounds use high-frequency sound waves that are emitted from a transducer, which is a small tool that is shaped like a wand. Sound waves are sent through the body by the receiver, which also records the waves that come back. When the sound waves hit the line between two types of tissue, they bounce back.

Some examples of these kinds of lines are those between fluid and soft tissue or between soft tissue and bone. The transducer records the waves and then sends the information to a nearby processing unit and viewer so that live pictures can be shown.

Here’s how the process usually works:

Step 1:

The patient is asked to lie down on an examination table or to get in a comfortable position. In some cases, the person may need to empty their bladder before the scan. In other cases, a full bladder may be preferred. Be sure that you are clear on what your doctor wants before the bladder scan takes place.

Step 2:

A water-based ultrasound gel is applied to the lower abdomen, typically around the pelvic area. This gel helps transmit sound waves and ensures a clear image.

Step 3:

The healthcare provider or technician then uses the bladder scanner to gently move a small ultrasound probe over the gel-covered area. The probe emits high-frequency sound waves, which bounce off the bladder and are detected by the device.

Step 4:

The bladder scanner calculates the volume of urine in the bladder based on the reflection of the sound waves. This information is displayed on the scanner's screen as a numerical measurement, usually in milliliters (ml) or cubic centimeters (cc).

Step 5:

The healthcare provider interprets the scan results to determine if the bladder is adequately emptied or if there is urinary retention. This information is essential for diagnosing and managing various urological conditions, such as urinary tract infections, urinary incontinence, and postoperative monitoring.

Bladder scans are non-invasive, painless, and provide a quick and accurate assessment of bladder volume. For instance, it is now estimated that 30 percent of men and 40 percent of women suffer from an Overactive Bladder (OAB). A bladder scan can help doctors diagnose this condition and then provide treatment to reduce the symptoms it produces.

A recent study of intensive care patients found that ultrasound scan usage was highly effective for measuring bladder volumes. Another study found that bladder scanners are highly suitable for clinical use due to their accurate measurements.

One more study entitled “Non-invasive bladder volume measurement for the prevention of postoperative urinary retention: validation of two ultrasound devices in a clinical setting” also found ultrasound scanning of bladder volume to be highly accurate. 

The study went on to recommend that bladder scanning be used before catheterization is even considered. The study authors said that a bladder scan can help “the clinician in making the right decision whether or not to catheterize, not too early (= unnecessary) but certainly not too late (= preventing bladder distention).”

Click here to learn more about the usage steps.

3.How to Best Prepare for a Bladder Scan

If you are scheduled to undergo a bladder scan in the future, the good news is that preparing for a bladder scan is a straightforward process that typically does not require any special or extensive preparations. Here is what you need to know about preparing for a bladder scan to ensure the procedure goes as well as possible.

●If your healthcare provider or nurse provides specific instructions or guidelines for the bladder scan, make sure to follow them carefully. These instructions may vary depending on the healthcare facility and the reason for the scan.

●While there is usually no specific requirement for hydration before a bladder scan, it's a good idea to maintain your regular fluid intake. Having a partially filled bladder can make it easier to obtain accurate results during the scan.

●In some cases, you may be asked to empty your bladder before the scan. This is particularly true if the purpose of the scan is to measure post-void residual (PVR) volume. Make sure to comply with any pre-scan voiding instructions provided by your healthcare provider.

●Wear comfortable and loose-fitting clothing that can be easily lifted or pulled aside to expose the lower abdomen, where the bladder scan will be performed. This will help facilitate the scanning process.

●If you have any concerns or questions about the bladder scan, don't hesitate to communicate with your healthcare provider or the technician performing the scan. They can provide you with any additional information or reassurance you may need.

Try to stay relaxed during the procedure. Bladder scans are typically painless and non-invasive. The technician will guide you through the process, and there should be minimal discomfort involved.


A bladder scan is a valuable tool for assessing and managing various urological conditions, including urinary incontinence, urinary tract infections, enlarged prostate (in men), and the effectiveness of interventions such as catheterization or medications.

It allows healthcare providers to make informed decisions regarding patient care and treatment strategies based on the information provided by the scan.

After you undergo the bladder scan, the radiologist will look over the results and send them right away to your doctor. Follow-up appointments are generally scheduled at least 48 hours after the initial scan. At your follow-up, your physician can go over the results with you and discuss future treatment methods, if required.


1.American Urological Association, Overactive Bladder (online). Accessed Oct. 3, 2023.

2.Schallom, M. et al (2021) Accuracy of Measuring Bladder Volumes with Ultrasound and Bladder Scanning in the ICU, National Library of Medicine, 29(6): 458–467.

3.Zheng, V. et al (2023) Accuracy of Bladder Scanner in Measuring Bladder Volumes in Postpartum Women, Northwestern University, 29(9): 777-783.

4.Brouwer, T et al (2018) Non-invasive bladder volume measurement for the prevention of postoperative urinary retention: validation of two ultrasound devices in a clinical setting, Journal of Clinical Monitoring and Computing, 32: 1117–1126.
Article by
David Smith
David is a urologist with over 9 years of experience. He is also the Co-fonder of BladGo, where he regularly shares his expertise in the field of urology. David is committed to keeping readers up-to-date on the latest urological research and to sharing other beneficial healthcare tips and information so that they can live healthier lives.

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