A bladder scanner is a portable, non-invasive ultrasound device that provides a quick and painless way to measure the volume of urine present in the bladder. This technology uses high-frequency sound waves to create a three-dimensional image of the bladder, calculating the volume based on the echoes received. The procedure is fast, typically taking only a few minutes, and is widely preferred over more invasive methods for estimating urine volume. The scanner’s function is to give healthcare providers immediate, accurate data about bladder contents at the point of care.
Clinical Reasons for a Bladder Scan
Bladder scanning is a standard procedure used to investigate symptoms related to urinary function. The test is frequently ordered to assess for urinary retention, which is the inability to fully empty the bladder, a condition that can lead to discomfort and potential complications. Measuring the amount of urine left after a patient voids, known as the Post-Void Residual (PVR) volume, is a major indication for the scan. An elevated PVR volume suggests issues such as bladder outlet obstruction, weak bladder muscle function, or neurological problems affecting bladder control.
The scan also helps in managing patients following surgery, as post-operative urinary retention is a common concern that requires timely assessment. Furthermore, a bladder scan assists in evaluating the potential causes of urinary incontinence, helping to differentiate between types like overflow incontinence or stress incontinence. By providing a non-invasive measurement, the scanner helps determine the necessity for catheterization, reducing the risk of catheter-associated urinary tract infections (CAUTIs) and urethral trauma. Regular scanning is also used to monitor individuals with neurological conditions like multiple sclerosis or spinal cord injuries that can impair bladder emptying.
Preparing for the Scan
Before the scan begins, the healthcare professional will ensure the patient is positioned correctly and comfortably, typically lying flat on their back. For some patients, bending the knees can help relax the abdominal muscles, which facilitates a clearer image. The lower abdomen must be exposed to allow direct contact between the skin and the scanner probe, with care taken to maintain patient privacy.
A water-based ultrasound gel is then applied directly to the patient’s abdomen, specifically in the midline area just above the pubic bone. This gel eliminates air pockets and allows the ultrasound waves to effectively transmit from the probe into the body, ensuring a high-quality image of the bladder. If the goal of the procedure is to measure the Post-Void Residual volume, the patient must be asked to empty their bladder immediately before the scan is performed. The scan should be completed within ten minutes of the patient voiding to ensure the most accurate residual volume measurement.
Step-by-Step Procedure
The initial technical step involves powering on the device and selecting the appropriate setting, such as male, female, or pediatric, as this calibration is necessary for the device’s internal algorithm to calculate the volume accurately. The operator must locate the pubic bone, which serves as the landmark for probe placement. The probe is positioned on the midline of the abdomen, roughly one to three finger-breadths above this bone.
Once the probe is placed on the gel, it must be aimed or angled slightly downward toward the patient’s tailbone, or coccyx, to direct the ultrasound beam into the pelvic cavity where the bladder is situated. The scanning process is initiated by pressing the designated scan button on the probe or console, which sends and receives the sound waves. The operator watches the screen for a clear cross-sectional image of the bladder, which appears as a dark, fluid-filled structure. If the initial image is not centered or clear, the operator gently tilts or moves the probe slightly to capture the largest diameter of the bladder.
Once the optimal image is obtained, the operator typically freezes the screen and activates the measurement function. This function uses the 3D data collected to calculate the total urine volume in milliliters. For the most reliable result, many protocols recommend repeating the scan two or three times to ensure consistency and then averaging the measurements.
Understanding the Results
The numerical result displayed by the bladder scanner represents the volume of urine in the bladder, typically measured in milliliters (mL). When a scan is performed immediately after a patient has attempted to urinate, the resulting number is the Post-Void Residual (PVR) volume. This PVR volume is what healthcare professionals use to determine the efficiency of bladder emptying.
A PVR volume below 50 mL is generally considered normal, indicating adequate bladder emptying in most adults. Volumes between 50 mL and 100 mL may be acceptable, particularly in older adults, but may warrant monitoring. A PVR volume consistently measured above 200 mL suggests incomplete bladder emptying and is considered abnormal. High volumes, particularly those exceeding 400 mL, are often indicative of significant urinary retention and may require immediate medical intervention to prevent complications like kidney damage or infection.