Department of Urology, University of Michigan, Ann Arbor, Michigan, USA.
Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
Neurourol Urodyn. 2021 Jan;40(1):85-94. doi: 10.1002/nau.24526. Epub 2020 Oct 5.
Paquin asserts that in order for ureterovesical junctions (UVJs) to prevent reflux, the ureteral tunnel length-to-diameter ratio needs to be 5:1. We hypothesize that the surgical implementation of this observation results in an overestimation of the needed length-to-diameter ratio to prevent vesicoureteral reflux.
With finite elements, we model the urine storage phase of the bladder under nonlinear conditions. In the reference state, the bladder is assumed to be a sphere with an oblique straight elliptical hole as the UVJ. Broad parametric studies on different length-to-diameter ratios are performed as the bladder volume increases from 10% to 110% capacity.
The capability of the UVJ to prevent reflux during storage depends on its length-to-diameter ratio. UVJs with larger length-to-diameter ratios lengthen and narrow as the bladder volume increases, causing the closure of the UVJ and rise in its flow resistance. Our model shows that the UVJ length-to-diameter ratio decreases as the bladder volume increases. The 5:1 ratio implemented at 80% capacity-approximate volume or bladder wall stretch during ureteroneocystostomy (UNC)-corresponds to 7:1 at the reference state-used by Paquin. The 5:1 ratio implemented at the reference state corresponds to 3:1 at 80% capacity.
Our modeling results are consistent with Paquin's original observation on the significance of the UVJ length-to-diameter ratio in preventing reflux. They, however, indicate that the surgical implementation of this rule during UNC results in an overestimation of the requisite tunnel length-to-diameter ratio to prevent reflux. They also suggest that the UVJ closure is due to the bladder wall deformation rather than the pressure.
Paquin 断言，为了防止输尿管膀胱连接处（UVJ）反流，输尿管隧道长度与直径之比需要达到 5:1。我们假设，这种观察结果的手术实施导致高估了预防膀胱输尿管反流所需的长度与直径之比。
我们使用有限元方法对膀胱在非线性条件下的储尿期进行建模。在参考状态下，假设膀胱为球体，UVJ 为斜直椭圆形孔。随着膀胱容积从 10%增加到 110%，对不同长度与直径之比进行广泛的参数研究。
UVJ 在储存过程中防止反流的能力取决于其长度与直径之比。长度与直径之比较大的 UVJ 随着膀胱容积的增加而延长变窄，导致 UVJ 关闭并增加其流动阻力。我们的模型表明，随着膀胱容积的增加，UVJ 的长度与直径之比减小。在 80%容量时实施的 5:1 比例（近似于输尿管膀胱再吻合术（UNC）期间的膀胱壁拉伸或容积）在参考状态下对应于 Paquin 使用的 7:1 比例。在参考状态下实施的 5:1 比例在 80%容量时对应于 3:1 比例。
我们的建模结果与 Paquin 关于 UVJ 长度与直径之比在防止反流中的重要性的原始观察结果一致。然而，它们表明，在 UNC 期间实施此规则会高估预防反流所需的隧道长度与直径之比。它们还表明，UVJ 的关闭是由于膀胱壁变形而不是压力。
