Ureteral peristalsis
Longitudinal wall motion during peristalsis and its effect on reflux
In these studies, we are aiming at better understanding less-studied subject of ureteral peristalsis. To do so, we have developed a simple lubrication model of peristalsis, which, for the first time, considers ureteral wall longitudinal motion. This longitudinal motion has been observed clinically as cyclic motion of the ureter between the bladder and the kidneys during peristalsis. We show that the ureteral wall longitudinal motion can prevent or limit peristaltic reflux.
Animations below are showing peristaltic reflux and the effect of wall longitudinal motion on it.
Example peristaltic reflux illustration. Two examples of pathlines in the laboratory frame are shown. The refluxing fluid particle with negative net displacement is shown with red (dashed pathline), while the non-refluxing particle with positive net displacement is shown in black (solid pathline). The empty circles show initial locations while the filled circles are showing locations at the end of one waveperiod. The peristaltic wave translates from left to right. The refluxing fluid particles can result into urinary stasis, urine accumulation and eventual dilation.
Wall motion during peristalsis without considering longitudinal effects: Shapiro et al. (1969) model. The peristaltic wave translates from left to right.
Wall motion during peristalsis with longitudinal effects. The peristaltic wave translates from left to right.
Wall longitudinal motion prevents peristaltic reflux. Compare this video with its counterpart without wall longitudinal motion in the first video.
Effect of wall longitudinal motion on peristalsis performance
(a) Peristaltic efficiency and (b) reflux fraction are plotted against urine volumetric flow rate in the pumping range for the normalized peristaltic amplitude of b/a = 0.8. The lines are showing the results without wall longitudinal motion i.e. the Shapiro et al. (1969) case, while the points are obtained with wall longitudinal motion. The refluxing conditions in (a) are shown with a dotted line and empty circles. In (b) the discrete points with zero reflux fractions are omitted for clarity. As shown, wall longitudinal motion not only can prevent peristaltic reflux, but in the events that it occurs (low peristaltic amplitudes) it limits it.
Related Publications
[1] K. Kalayeh, H. Xie, J. Brian Fowlkes, B. S. Sack and W. W. Schultz, “Longitudinal wall motion during peristalsis and its effect on reflux,” Journal of Fluid Mechanics, vol. 964, 2023. http://dx.doi.org/10.1017/jfm.2023.363
[2] K. Kalayeh, J. B. Fowlkes, H. Xie, W. W. Schultz and B. S. Sack, “Peristalsis prevents ureteral dilation,” Neurourol Urodyn, 2023. https://www.ncbi.nlm.nih.gov/pubmed/37961019