Simultaneous measurement of urethral opening pressure and urethral cross-sectional area during voiding cystometry

To assess a new technique for measuring urethral opening pressure and urethral cross-sectional area during the course of routine voiding cystometry.

Twenty-eight male patients were studied, 24 of whom had cystometric evidence of bladder outlet obstruction, the other four being unobstructed. Urethral opening pressure was measured using an adapted fluid bridge test and urethral cross-sectional area was measured using the method described in the preceding paper.

The mean urethral opening pressure in the obstructed patients was 68 cm/H2O (range 38-124) against a mean of 19 cm/H2O (range 16-22) in the unobstructed group. The mean urethral cross-sectional area in the obstructed group was 2.6 mm2 (range 0.9-7.9) compared with a mean of 14.2 mm2 (range 10.8-19.9) in the unobstructed patients.

This technique allows measurement of the parameters of bladder outlet obstruction described by Schäfer during routine voiding cystometry, without specialized equipment. This provides a simple method for quantification of urinary outflow obstruction and should prove useful in the assessment of new treatment modalities.