Urinary bladder volume measurements: comparison of three ultrasound calculation methods

To assess the precision of three different automatic calculation methods in real-time bladder volume measurement.

Bladders from 34 medical staff volunteers were examined. Two examinations of each subject were performed independently by 2 examiners using 2 identical ultrasound scanners with no delay between the examinations. Three different automatic calculation algorithms, available as software in the ultrasound scanner, were applied on the frozen ultrasound pictures. After registration of the voided volume with an uroflowmeter, the subjects were scanned again in order to assure complete emptying.

Voided volumes ranged from 45 ml to 508 ml. The precision of each method was equal but the LWH method measured significantly lower values than the ELLIPSOID and AREA method. Errors in the range of -56.1% to +58.8% for all volumes and methods were found. Data for voided volumes greater than 150 ml (n = 29) were investigated separately, but no significant improvement in accuracy for any of the methods was found.

Ultrasound bladder volume calculation is an easy method for estimation of bladder volume. The prolate ellipsoid method (LWH) is recommended as the standard calculation method because it is fast and easy. Unacceptable large measure errors are found and too rigid conclusions based on ultrasound measurements of bladder volume should be avoided.