Serial residual volumes in men with prostatic hypertrophy.

Thirty men with prostatic hypertrophy were scanned on 3 occasions on the day before TURP. Five commonly used formulae to estimate residual urine were used. All of these methods are subject to large degrees of error; 66% of these patients had residual volumes that varied significantly on the same day. We suggest that it is of no clinical value to perform a single residual urine measurement in patients with prostatic hypertrophy.