Urethral sphincter volume and urodynamic diagnosis

To compare urethral sphincter measurements in women with different urodynamic diagnoses using three-dimensional transperineal ultrasound (TPU).

Women with lower urinary tract dysfunction having urodynamic studies (UDS) were prospectively recruited to this study. A detailed history and vaginal examination were conducted. Saline cystometry was performed and the women were divided into groups according to their urodynamic diagnosis, which were nondiagnostic urodynamics (NUDS), pure detrusor overactivity (PureDO), pure urodynamic stress incontinence (PureUSI) and mixed urinary incontinence (MUDS). Three-dimensional TPU was performed to measure total urethral sphincter volume, striated sphincter volume, core volume, sphincter length and maximum cross-sectional area. The ultrasound measurements were compared with the diagnostic urodynamics.

One hundred fifty women were included in the study. There were 37, 53, 22 and 38 women in the groups of NUDS, PureDO, PureUSI and MUDS respectively. The average striated sphincter volumes in these groups were 1.84 ml, 2.24 ml, 1.32 ml and 1.98 ml respectively. There was no difference in average age, body mass index or presence of prolapse in these groups. All measurements were larger in the PureDO and smaller in the PureUSI group compared with the NUDS group. The measurements in the MUDS group were larger than in the NUDS group and smaller than in the PureDO group but this difference was not statistically significant.

The urethral sphincter of women with PureDO is larger than in women with PureUSI. The value in women with MUDS was between the two. The size of the urethral sphincter appears to be related to the pathophysiology.