Radical prostatectomy restores detrusor contraction pattern according to pressure flow parameters

Abstract

Objectives: Pressure flow studies are regarded as the gold standard for evaluating both bladder outlet obstruction and detrusor contractility, but none of the current methods for evaluating bladder contraction patterns are well validated. Impaired bladder contraction results in a lower peak Watts factor and poorly sustained detrusor contractions. From this viewpoint, the maximum Watts factor and its pattern should be considered separately. To examine detrusor contraction pattern in patients after radical prostatectomy by using multiple parameters. Methods: A total of 37 patients with clinically localized prostate cancer underwent both pre- and post-radical prostatectomy urodynamic evaluations. The examined urodynamic parameters included the maximum flow rate, post-void residual volume, detrusor pressure at maximum flow, maximum Watts factor and relative volume (maximum Watts factor). Some parameters were defined from the Watts factor curve throughout micturition. Relative volume (maximum Watts factor) was the relative bladder volume at the maximum Watts factor. A normal detrusor contractility pattern involves an increase in Watts factor at the initiation followed by further gradual increases until the end of micturition. Results: Maximum flow rate increased significantly after radical prostatectomy (pre: 13.0 ± 6.5, post: 17.3 ± 7.7 mL/min; P < 0.01), whereas detrusor pressure at maximum flow and post-void residual volume decreased significantly (pre: 49.6 ± 21.6 and 31.4 ± 18.2 cmH 2 O; post: 48.6 ± 66.1 and 10.1 ± 28.5 mL; P < 0.05). Maximum Watts factor did not change significantly after radical prostatectomy (pre: 10.5 ± 3.1 W/m 2 , post: 11.0 ± 3.2 W/m 2 ), but relative volume (maximum Watts factor) decreased significantly (pre: 0.48 ± 0.3, post: 0.20 ± 0.20; P < 0.001). Maximum Watts factor represents the maximum power of bladder contraction at a particular point in time, whereas relative volume (maximum Watts factor) can be used to detect changes in detrusor contraction pattern. Conclusions: Evaluation of relative volume (maximum Watts factor) confirms that radical prostatectomy restores the normal detrusor contractility pattern in prostate cancer patients.