Laudário Calculators Bladder volume
Bladder volume and post-void residual calculator
Enter the three bladder measurements before and after voiding. The volume comes out from the ellipsoid formula, with the interpretation of the residual and the sentence for the report.
Patient
Pre-void
Volume: —
Post-void
Residual: —
Result—
Sentence for the report
Volume = longitudinal x transverse x anteroposterior x 0.52. Commonly used residual cut-offs (adult: above 100 mL significant and above 200 mL elevated; child: above 20 mL or 10% of the pre-void volume); they may vary according to the department’s protocol.
How to measure
- Longitudinal and anteroposterior on the sagittal view, at the largest dimension.
- Transverse on the axial view, at the largest dimension.
- Measure the post-void volume right after voiding, ideally within 10 minutes.
- Very irregular bladders (diverticula, trabeculation) have their volume underestimated by the formula, which deserves a caveat in the report.
See also the kidney and urinary tract report template.
Frequently asked questions
How do you calculate bladder volume on ultrasound?
The bladder is measured in its three axes (longitudinal, transverse and anteroposterior) and the product is multiplied by 0.52, the ellipsoid formula. The result in cubic centimeters is equivalent to milliliters.
Is there a normal pre-void bladder volume?
There is no single normal value: the pre-void volume is how much the bladder held before voiding, used to judge whether filling was adequate and to compare with the residual. In adults, bladder capacity is usually between 300 and 500 mL. In children, expected capacity is estimated as (age in years + 2) x 30 mL. Cut-offs vary between protocols.
What is a normal post-void residual?
In adults, residuals up to about 50 mL are considered normal, and above 100 mL are usually significant. In children, the absolute value (above 20 mL) and the proportion of bladder capacity (above 10%) are used. Cut-offs vary between protocols.
How long after voiding should the residual be measured?
As soon as possible, ideally within 10 minutes after voiding, so that refilling does not add to the residual.
In Laudário, volumes are calculated inside the report.
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