The trans-obturator tape (TOT), which exhibits a satisfactory cure rate and a relatively diminished invasiveness, has been increasingly accepted as a surgical treatment of stress urinary incontinence (SUI) patients. Nevertheless, in contrast to the well-recognized therapeutic benefit of the enhanced resistance to the bladder continence during urine storage, if the voiding function of the bladder adapts to the TOT-enhanced outlet resistance has not been adequately investigated. This study retrospectively assayed the voiding efficacy of each voiding cycle, to clarify if the thermodynamic efficacy of the bladder was modified in response to the TOT surgery.