Pressure-volume analysis of thermodynamic workload of voiding - an application in pelvic organ prolapse patients subjected to robotic-assisted sacrocolpopexy

Purpose: Given objective benefits of robotic-assisted sacrocolpopexy (RSCP) to the voiding function/deficit of patients with pelvic organ prolapse (POP) waits to be clarified, this study investigated if RSCP modifies voiding functions of POP patients by focusing on its impact on the outlet resistance-dependent voiding workload using pressure-volume analysis (PVA), a protocol thermodynamically assaying work expenditure by the bladder in voiding cycles. Methods: Pre- and post-operative cystometry and PVA of 22 female patients, who underwent RSCP for POP (stage ≥ II), were reviewed. Mean voiding resistance (Rvod), mean voiding pressure (Pvod), mean voiding flow (Fvod), voided volume (Vvod), voiding time (Tvod), and the trajectory-enclosed area (Apv) were analyzed. Results: The PVA, in which trajectory shaped an enclosed loop representing a voiding cycle, was established by adapting from the time-domain cystometry. Compared to the pre-operative control, RSCP decreased Rvod, Pvod, and Tvod (p = 0.003, 0.042, and 0.040, respectively. All N = 22) but increased Fvod (p = 0.036, N = 22) without markedly affecting Vvod (p = 0.580, N = 22). Apv was decreased after RSCP (p = 0.017, N = 22). The RSCP-decreased Rvod (ΔRvod) displayed a moderate correlation with both the decreased Pvod (ΔPvod, r = 0.551, p = 0.007, N = 22) and the increased Fvod (ΔFvod, r=-0.625, p = 0.001, N = 22). The ΔFvod moderately correlated with the decreased Tvod (ΔTvod, r=-0.620, p = 0.002, N = 22). Moreover, the RSCP-decreased Apv (ΔApv) displayed correlation with the ΔPvod (r = 0.385, p = 0.047, N = 22). Conclusions: Through diminishing outlet resistance of POP patients, RSCP not only prompted urine emission thereby increased voiding efficacy but also decreased the pressure developed for driving urine flow that lessened voiding workload. Clinical Trial Registration ClinicalTrials.gov (NCT05682989).