Detrusor-Overactivity-Related Voiding in Women Mimics Bladder Outflow Obstruction and Conceals Underactivity

Urodynamics of the storage phase showing detrusor overactivity is com- mon in neurogenic bladder patients. Terminal detrusor overactivity, which is defined by involuntary detrusor contraction that cannot be inhibited, causes urinary incon- tinence. Such incontinence causes a unique voiding in neurogenic bladder patients. During the voiding phase, the detrusor pressure at Qmax (Pdet.Qmax)/maximum flow rate (Qmax) (P/Q) is the gold standard for differentiating between detrusor underactiv- ity and bladder outflow obstruction. We investigated whether a valid identification of lower urinary tract dysfunction could be established from P/Q assessment of detrusor overactivity-related voiding patients.

This study evaluated 2 types of voiding. Detrusor overactivity-related void- ing is involuntary detrusor contraction that results in micturition or voiding after per- mission to void when detrusor overactivity has occurred, while voluntary voiding is voiding voluntarily after permission to void and without terminal detrusor overactivity. We evaluated female patients with neurogenic bladder who could undergo micturition without catheterization. A pressure flow study compared the 2 groups.

Comparison of the detrusor overactivity-related voiding group (n=20) and the voluntary voiding group (n=12) found statistically significant differences with a lower Qmax and higher Pdet.Qmax (P=.01) in the detrusor overactivity-related void- ing group. The linear regression analysis P/Q plot showed the positivity and negativity value of the slope that was reversed in the 2 groups (-0.089 vs. 0.198).

Current results showed different P/Q plot patterns between 2 types of voiding in patients with neurogenic bladder. These findings suggest there is increased detrusor pressure observed in detrusor overactivity-related voiding that mimics out- flow obstruction.