Measurement of bladder volume by real-time ultrasound.

The accuracy of a non-invasive method of measuring the volume of urine in the bladder using ultrasound was assessed 32 times in 18 patients with benign prostatic hypertrophy. A method originally used with B-mode scanners was applied to images obtained with a real-time scanner. Although the mean error of 8% of true volume (range -29% to +52%, standard deviation 23%) compared favourably with that of some series, the results were less accurate than those originally reported for this method using a B-mode scanner. Real-time ultrasound can provide an approximate measurement of bladder urine volume but is not sufficiently accurate in situations where more precise measurements of changes in residual urine are required.