Transrectal ultrasound to measure bladder volumes in men.

Transrectal linear array ultrasound is described as a method in men to measure bladder volumes of 5 to 200 ml., overcoming the limitations of abdominal ultrasound at these smaller, although clinically important volumes. The mean error in a preliminary series with known volumes of 10 to 175 ml. was 18%. Statistical analysis of these data shows that an unknown bladder volume in milliliters can be calculated from the measurement of 2 sagittal bladder diameters, the height and depth, by the formula volume (ml.) = 5.3 X (height X depth) - 21. This equation when applied to measurements of a series of unknown bladder volumes had a mean error of 16%. Transrectal ultrasonic measurement of residual urine volumes (mostly those less than 175 ml.) provides a useful complement to visualization of the prostate by transrectal ultrasound.