A bladder scan is a non-invasive diagnostic procedure that uses portable ultrasound technology to measure the volume of urine inside the bladder. This technique is frequently used to assess post-void residual (PVR) volume, which is the amount of urine remaining after a person has attempted to urinate. Determining the PVR volume is important for evaluating urinary disorders such as retention or incomplete bladder emptying. Unlike invasive methods like catheterization, the bladder scan provides a quick, safe, and comfortable alternative for estimating bladder volume.
Preparing the Patient and Equipment
The procedure begins by ensuring patient privacy and comfort, positioning the individual flat on their back (supine position) with the lower abdomen exposed. If measuring PVR, confirm the patient attempted to void within the preceding ten minutes, as accuracy decreases with delay. Portable bladder scanners require activation and setup, including selecting the correct patient profile. The gender selection must be set to “female” mode, as the machine’s algorithm needs to account for pelvic anatomy. Acoustic coupling gel is then applied to the lower abdomen, just above the pubic bone, to facilitate ultrasound transmission.
Executing the Bladder Scan Procedure
The scanning technique begins with initial probe placement approximately 2 to 3 centimeters above the symphysis pubis (the midline joint between the pubic bones). The operator aims the probe slightly downward (caudally) toward the patient’s tailbone. This downward angle directs the ultrasound waves beneath the pubic bone and into the pelvic cavity where the bladder is situated. The probe must be held steady with gentle, firm pressure to maintain skin contact and ensure good image quality.
The scanner displays a real-time image, showing the bladder as a dark, fluid-filled circle or oval. The operator slowly sweeps the probe across the area to find the point where the bladder image is largest and most centered. Locating this maximum diameter ensures the device captures the bladder’s full dimensions for accurate calculation. Once the optimal image is obtained, the measurement function is activated to calculate the three-dimensional volume in milliliters.
Adjusting the Scan for Female Anatomy
Scanning a female patient requires specific adjustments because the uterus can overlap the bladder and interfere with ultrasound waves. If the scanner is not set to the female/non-pregnant mode, or if the uterus is tilted forward (anteverted), it can obscure the bladder dome, resulting in an artificially low reading. To mitigate this interference, increase the downward tilt of the probe, angling it more steeply toward the tailbone. This steeper angle helps the ultrasound beam capture the bladder entirely beneath the uterus.
For patients who have had a hysterectomy, the “male” setting is preferred, as the female setting compensates for an organ that is absent. If the initial scan yields an irregular bladder shape or a low confidence reading, the operator should try scanning from a slightly higher position on the abdomen. Documenting factors like pregnancy or recent pelvic surgery is important, as these anatomical variations influence the accuracy of the volume measurement.
Interpreting Results and Next Steps
The bladder scanner provides the final urine volume measurement in milliliters (mL). A PVR volume of less than 50 to 100 mL is considered normal, suggesting effective bladder emptying. A measurement consistently above 100 mL often suggests incomplete emptying and requires further medical evaluation. Readings exceeding 200 mL to 300 mL are considered significant and may prompt clinical intervention to prevent complications.
Once the measurement is recorded, the acoustic gel must be completely wiped from the patient’s abdomen and the scanner probe. The final step involves accurately documenting the volume, the time of the scan, and any complicating factors, such as difficulty obtaining a clear image, in the patient’s medical record.