Main findings
Though, USA Food and Drug Administration had a press announcement concerning the long-term safety10, TVM is still an option for POP reconstruction because it offers satisfied anatomical and objective outcomes12. In contrast to studies consistently demonstrating advantages of TVM on the voiding19,20, the current study explored the potential benefit of TVM to the storage function by specifically focusing on the bladder compliance.
Our results reveal TVM post-operatively increased bladder compliance of POP patients, namely the bladder displayed a reduced pressure in response to the storage volume during the filling stage. The TVM-increased compliance could benefit POP patients, because aberrantly elevated intra-vesical pressure during storage is deleterious as it would cause vesico-ureteral reflux2, over-activate the micturition reflex21, and result in stress urinary incontinence22.
Notably, in contrast to urodynamic studies analyzing the bladder compliance by dividing the change in volume by that in pressure (C=ΔV/ΔP); and thereby offer a mean value of compliance over the entire filling stage23, a recent study exploring compliance dynamics has demonstrated PVA not only graphically and conceptually assesses the bladder compliance but also provides a protocol that is able to specifically analyze compliance of targeted periods during bladder filling18.
PVAs in this study demonstrates while the post-operative trajectory displayed a relatively constant slope during entire filling, the pre-operative trajectory markedly deviated to the right and downwards at the late filling stage, indicating the compliance was decreased specifically at this stage. The decreased compliance in the late filling of pre-operative patients was confirmed as the patient statistically displayed a lower C2/2 compared to C1/2. Even though a clear-cut value defining a low bladder compliance waits to be established, studies have reported a level of low compliance in human from 12.5 to 40 ml/cmH2O3,24,25. Considering our mean C1/2 before TVM were 105.82±16.41 ml/cmH2O, a value far higher than these levels, we suggest the impaired compliance in POP patients is possibly attributed to the compliance decrement at the late filling.
On the other hand, while the TVM-increased Cm was associated with post-operatively enhanced C2/2, the C1/2 remained relatively unaffected after the procedure. Together with that the post-operative Cm (103.01±13.44 ml/cmH2O), C1/2 (116.13±12.92 ml/cmH2O), and C2/2 (112.84±21.57 ml/cmH2O) in this study were all higher than the reported level of low compliance, these findings collectively reveal TVM benefits to the storage function of POP patients by specifically ameliorating the impaired compliance during the late filling.