The accuracy of ultrasound in the measurement of changes in bladder volume.

Ultrasound is an established method of assessing bladder and residual urine volumes. The aim of this study was to improve the accuracy of ultrasound in measuring changes in bladder volume and to avoid bladder catheterisation. Seventeen patients took part in the trial; their bladders were scanned before and after micturition and bladder volumes were estimated. Fifteen patients had bladder outflow obstruction. Further mathematical analysis showed that a correction factor yielded greater accuracy in measuring bladder volume (mean error 21% in this series against 28% in previous studies). Ultrasound is a quick, non-invasive and quantitative method of studying bladder volume, especially in the conservative management of patients with bladder outflow obstruction.