Non-invasive urine volume measurement is an important tool in the management of dysfunctional and neuropathic bladders in children. Ultrasound imaging devices have been used for many years for this purpose. An automated scanner (Bladderscan) is now available and has been recommended by a number of authors, but there is conflicting evidence in the literature regarding the accuracy and appropriate clinical application of the device. We aimed to assess the level of clinical agreement between the two methods. 36 urine volume measurements were made on 11 children using both instruments. Although there was a good correlation between the methods (r=0.97), the clinical agreement was poor (limits of agreement +/-77 ml). 13 voided volumes were directly measured and compared with the difference between pre- and post-void ultrasound measurements. The systematic errors were small but the mean absolute errors were 54 ml and 23 ml, respectively, for the automated and ultrasound imaging methods. If used correctly, ultrasound imaging provides more accurate results and can compete with the cost, convenience and ease of use of the automated method. Low cost, highly portable ultrasound imaging devices are now available and should be used in preference to the Bladderscan.

Portable bladder ultrasound is a necessary investigation in urology and other disciplines. Scanners image with or without bladder wall detection--others provide only numeric readout. In volunteers, we compared measurements from four current scanners. Methods: Bardscan, Verathon BVI3000, Verathon BVI6100 and Sonosite iLook15 were used with 28 healthy volunteers, with scanners in random order. Ordinary least squares regression modelled the measured volumes of each volunteer using each scanner. For each patient-scanner combination, the predicted volume from this model (corrected for the average bias of each scanner) represents the best estimate of the volume, and the difference between the measured bladder volume and the predicted volume was an estimate of the error of that measurement. Results: The iLook15 and Bardscan underpredict, and the BVI3000 and BVI6100 overpredict, relative to the average of the four scanners (p < 0.05). The BVI3000 had slightly greater error variability than the others (p = 0.051). Measurement error appears more variable for larger volumes. Conclusion:The two real-time imaging systems (the SonoSite iLook15 and the Bardscan) tended to give lower volume estimates than the two systems from the same manufacturer (the BVI3000 and BVI6100). Of the two BVI scanners, the 6100 had markedly less variable error.

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