Objective In contrast to the well-recognized benefit of trans-obturator tape (TOT) to urine continence, if the TOT-enhanced urethra resistance results in modified voiding functions in stress urinary incontinence (SUI) patients is not adequately investigated. Design and setting Urodynamic investigations were retrograde analyzed in a tertiary referral hospital. Population A total of 26 female SUI patients Methods The area enclosed by the loop trajectory (Apv) in a pressure-volume analysis (PVA) which represent the work performed in each voiding cycle was retrospectively analyzed Main outcome measures The Apv of female SUI patients before and after the TOT were analyzed. Results When compared with the pre-operative control, the Apv was significantly increased post-operatively. The TOT-enhanced Apv was accompanied by increments in the mean urethra resistance (Rv) and mean voiding pressure (Pv) but unaffected voided volume (Vv) and voiding time (Tv). Moreover, the TOT-induced Apv increase (ΔApv) displayed moderate correlations with the changes in Rv and Pv (ΔRv and ΔPv, respectively) but no correlation with the changes in Vv or Tv (ΔVv and ΔTv, respectively). Notably, the TOT-induced ΔRv displayed a strong correlation with the ΔPv. Conclusions: The thermodynamic efficacy of the bladder was enhanced after the TOT; that could be attributed to that bladder develops an elevated pressure gradient in response to the TOT-enhanced outlet resistance during urine emission. Keywords: mid-urethra sling, trans-obturator tape, stress urinary incontinence, urethra resistance, thermodynamics, pressure-volume analysis Tweetable abstract The bladder developed an elevated pressure gradient to the TOT-enhanced outlet resistance; and herein enhanced the voiding efficacy.