A bladder scan is a straightforward, non-invasive imaging procedure that uses a portable ultrasound device to determine the amount of urine currently held within the bladder. This quick measurement is performed externally, typically in a hospital setting or an outpatient clinic, to gather immediate diagnostic information. The procedure is painless and provides a precise numerical value, expressed in milliliters, representing the bladder’s volume at that moment. It offers a fast, comfortable alternative to more invasive methods of checking for urinary issues.
How the Technology Works
The bladder scanner operates using the principles of ultrasound technology. A handheld device, known as a transducer or probe, is placed on the lower abdomen to send sound waves into the body. When the waves encounter internal structures, such as the fluid-filled bladder, they reflect back as echoes to the probe.
The device captures these returning echoes and transmits the data to its internal computer software. This specialized software processes the time and intensity of the echoes to create a three-dimensional representation of the bladder. The system automatically calculates the total volume of urine present, displaying the result on the scanner’s screen within seconds. This process is accurate because the sound waves travel cleanly through the liquid urine, providing a clear boundary for the software to measure.
Medical Reasons for Performing the Scan
The main clinical application of a bladder scan is to measure Post-Void Residual (PVR) volume. An elevated PVR volume suggests that the bladder is not emptying effectively, which can be an early sign of various urinary dysfunctions. Clinicians use this measurement to diagnose or monitor conditions that cause incomplete bladder emptying, such as bladder outlet obstruction, often caused by an enlarged prostate in men.
The scan identifies acute urinary retention, a potentially serious condition where the bladder cannot void at all. Regularly tracking the PVR volume helps evaluate the function of the detrusor muscle. Furthermore, by identifying an incomplete void, the scan can indirectly alert providers to an increased risk of urinary tract infections, as stagnant urine provides a favorable environment for bacterial growth. This diagnostic tool is routinely used to assess bladder function in patients with certain neurological conditions, such as multiple sclerosis or diabetic neuropathy, that can affect nerve signaling to the bladder.
What to Expect During the Scan
The bladder scan procedure is simple and requires minimal preparation from the patient. If the goal is to measure PVR, you will first be asked to urinate fully and the scan will be performed immediately afterward, ideally within ten minutes. You will be positioned comfortably, either lying down on your back or sometimes sitting upright, with your lower abdomen exposed.
A healthcare professional will apply a small amount of clear, water-soluble gel to your skin over the pelvic area just above the pubic bone. The gel enhances the transmission of sound waves from the probe into your body. The technician will then gently press the handheld probe onto the gel and move it across the area to capture the necessary images for volume calculation. The entire process is painless and generally takes less than five minutes to complete.
Interpreting the Volume Measurements
In a healthy adult under 65, a PVR volume of less than 50 milliliters is generally considered a sign of normal, complete bladder emptying. For older adults, a volume up to 100 milliliters may still be considered acceptable, as bladder function can change with age.
When the PVR volume falls between 100 and 200 milliliters, it may suggest mild retention or incomplete emptying, often leading to monitoring and advice. A PVR volume consistently measured at 200 milliliters or greater indicates significant bladder dysfunction and is a threshold for concern. This elevated volume may signal the need for more aggressive treatments, such as adjusting medication dosages or initiating intermittent catheterization to prevent complications like kidney damage or severe urinary tract infections.