Quantification of bladder outlet obstruction by measurement of urethral opening pressure using an adapted fluid bridge test.

A new technique for measuring urethral opening pressure above the distal sphincter is described, based on the fluid bridge test. This test eliminates many of the inaccuracies produced when using standard pressure flow studies. Nineteen males were studied, 15 of whom had cystometric evidence of bladder outlet obstruction, the other 4 being unobstructed. The mean urethral opening pressure in the obstructed group was 69 cm H2O (range 44-124) and in the unobstructed group 19 cm H2O (range 16-22). The test is simple to perform and is not affected by muscular activity in the pelvic floor or the time lag between detrusor pressure and flow rate measurement.