Direct recording of urethral resistance using the "urethroresistance".

Observations on urethral resistance during micturition in non-obstructed men and in patients with bladder outlet obstruction owing to benign prostatic hypertrophy are presented. The "Urethroresistance", a new instrument, was used for the direct recording of urethral resistance. The upper limit for the minimum urethral resistance during micturition for normal non-obstructed men was 0.5 units. Two patterns of urethral resistance were observed solely in non-obstructed subjects and 3 other patterns, which were found solely in patients with a moderate or severe degree of bladder outlet obstruction, were shown to be characteristic of bladder outlet obstruction. While direct recording of urethral resistance is a better test for bladder outlet obstruction than the recording of urinary flow rate the recording of urinary flow is a simple urodynamic test, which remains a useful screening test for bladder outlet obstruction. With the exception of severe obstructive symptoms none of the other clinical methods for the assessment of bladder outlet obstruction--the size of the prostate gland, the volume of post-micturition residual urine and the degree of bladder trabeculation--is reliable to determine the degree of bladder outlet obstruction.