Presentation Authors: Andrea Balthazar*, Zachary Cullingsworth, Naveen Nandanan, Uzoma Anele, John Speich, Adam Klausner, Richmond, VA
Introduction: In studies aimed at developing novel urodynamic (UD) metrics, our group previously identified the biomechanical properties strain softening (SS) and dynamic elasticity (DE). During the UD protocol, repeat filling and passive bladder emptying resulted in a reduction of intravesical pressure, SS. Active voiding reverses SS restoring baseline pressure termed DE. Importantly DE shows, in contrast to previous beliefs, that bladder compliance can be acutely regulated. Because filling and passive emptying requires an invasive catheter, we hypothesized that bladder SS can be produced noninvasively using an external compress-release protocol. The aim was to determine if SS produced by filling and passive emptying is equivalent to SS produced by repeated external compress-release in a porcine bladder model.
Methods: Ex vivo perfused porcine bladders were used for both passive emptying and external compress-release experiments. Passive emptying protocol, fig 1A: the bladder was filled to 250 ml (pre-SS pressure) and filling was continued to 500 ml (reference pressure). Then, the bladder was passively emptied via syringe aspiration to 250 ml (post-SS pressure). Next, the bladder was voided with high KCl buffer to induce â€œactiveâ€ contraction and refilled back to 250 ml (post-void pressure) to demonstrate DE. Compress-release protocol, fig 1B: the bladder was filled to 250 ml, and external compression was applied to isovolumetrically increase intravesical pressure to the reference pressure. The compression was held for 15s and released for 15s for 5 cycles. Equilibrium pressure 5 min after release (post-SS) was noted. In both studies, the following pressures were compared: pre-SS, post-SS, post-void.
Results: Ten bladders were studied. SS was demonstrated in both the passive emptying (p < 0.05) and compress-release (p < 0.05) protocols. The pressure after filling and passive emptying was not statistically different from the pressure after compression-release (p>0.05). The data suggests each method induced a similar degree of SS, fig 1C.
Conclusions: Repeat external compression of the bladder can induce a similar degree of SS as compared to filling and passive emptying. This technique may represent a potential means to acutely regulate bladder compliance and be used as a therapy to treat urinary urgency.
Source of Funding: NIH grant R01DK101719