Also called: Bladder scanner, Bladder volume scanner, Post-void residual
Bladder Scanner: Portable Bladder Volume Measurement
A bladder scanner measures urine volume at the bedside in seconds, without a catheter. How it works, where it helps, where it can mislead and what to check before buying.
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How a bladder scanner works
A dedicated bladder scanner is a small ultrasound device built for one job. The probe is placed above the pubic bone and sweeps the bladder in several planes; software finds the bladder outline and calculates the volume in millilitres. Many show an aiming guide rather than a diagnostic image, so the user does not have to interpret anatomy. Verathon’s BladderScan is the best-known brand, which is why “bladder scan” is often used for any make.
Bladder volume
How much urine is in the bladder now — for suspected retention, before deciding on catheterisation, or to time intermittent catheterisation.
Post-void residual (PVR)
The volume left straight after the patient passes urine — a routine measure in continence, urology, rehabilitation and post-operative care.
Repeat checks
With no catheter and no radiation, the measurement can be repeated as often as the care plan requires.
Who uses bladder scanners
- Hospital wards and recovery areas — checking for retention after surgery and after spinal or epidural anaesthesia.
- Stroke, spinal and rehabilitation units, where bladder function is monitored routinely.
- Urology, continence and gynaecology clinics measuring post-void residual.
- Nursing homes and home care — assessing retention without transferring the patient.
- Teams working to avoid unnecessary urinary catheters, a leading source of catheter-associated urinary tract infection (CAUTI).
- Paediatric units, using devices with a validated paediatric mode.
Accuracy and its limits
Bladder scanners answer “how much urine is there?” well when the bladder is the only fluid-filled structure in view. Readings can mislead when something else looks like urine or the bladder is hard to see. When a reading does not fit the clinical picture, confirm it another way — for example with an in-out catheter or a formal ultrasound.
| Situation | Why the reading may mislead |
|---|---|
| Obesity or deep abdominal tissue | The bladder may be partly out of range or poorly outlined |
| Ascites, ovarian or other pelvic cysts | Other fluid can be counted as urine and overestimate the volume |
| Pregnancy | Many devices are not intended for use in pregnancy — check the maker’s instructions |
| Scars, dressings, stomas or hernias | Poor probe contact or shadowing over the scan area |
| Catheter in place or very small volumes | Low volumes and catheter balloons can give unreliable figures |
| Poor aiming | Repeat the scan, use the aiming guide and take the most consistent reading |
Dedicated scanner or a general ultrasound?
A general ultrasound machine with a bladder package works out volume from three measured diameters multiplied by a correction factor (often about 0.52), and shows the anatomy at the same time. A dedicated scanner trades that flexibility for speed and simplicity.
| Dedicated bladder scanner | General ultrasound with bladder calculation | |
|---|---|---|
| Who uses it | Nurses and care staff after short training | Clinicians or sonographers trained in ultrasound |
| What it shows | A volume figure, often with an aiming guide | A full image, plus volume from measured dimensions |
| Other uses | Bladder volume only | Kidneys, abdomen, pregnancy and more |
| Best for | Wards, nursing homes, repeated routine checks | Clinics that also need diagnostic scans |
Read next Point-of-care ultrasoundPortable ultrasound options
What to check before buying
- Accuracy data from the maker, and the volume range it was tested over.
- A paediatric mode, if you scan children.
- Battery life and charging — it should last a full shift.
- How results are recorded: printout, on-device memory or transfer to the patient record.
- Probe cleaning: it touches intact skin, so clean and low-level disinfect it between patients with a product the maker approves.
- Performance checks, service arrangements and probe warranty.
- The MDA registration number for the device.
Read next Probe cleaning and disinfectionMaintenance and service
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Frequently asked questions
What is a bladder scanner used for?
Is a bladder scanner the same as an ultrasound machine?
Can nurses use a bladder scanner?
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