This study investigates tissue responses after laser irradiation of the rabbit ureter, which serves as an experimental model for rectourogenital fistulae of children. Twenty-five rabbit ureters were irradiated intraluminally by a Nd:YAG laser 1320 nm (2 Watt, 20 seconds and 3 Watt, 8 seconds) via an applicator with radialsymmetrical light distribution. Immediately, 2 weeks, 4 weeks, 8 weeks, and 16 weeks after irradiation, the ureters were X-rayed with contrast solution and prepared for light and transmission electron microscopy. For the parameters employed, no apparent morphological differences could be observed. Immediately, the central laser zone showed a transmural therrnonecrosis prevailed by cellular destruction, condensed ground substance and occlusion of most vascular lumina. Peripheral laser zones displayed urothelial vacuolations. Between 2 and 16 weeks, urothelial regeneration and ingrowth of granulation tissue caused a luminal stenosis or occlusion followed by transformation into scar tissue. In some peripheral laser zones, a hydroureter with marked luminal dilatation developed. We conclude that the ureter is occluded if the expanding force of the growing scar tissue exceeds the hydrostatic pressure of the obstructed urine. A laser occlusion of rectourogenital fistulae will be easier to achieve since fistula occlusion does not entail an obstruction of the urine flow.
Stratmann, U.; Schaarschmidt, K.; Lehmann, R. R.; Heinze, A.; Willital, G. H.; and Unsold, E.
"The Interaction of Laser Energy with Ureter Tissues in a Long Term Investigation,"
Scanning Microscopy: Vol. 9
, Article 17.
Available at: https://digitalcommons.usu.edu/microscopy/vol9/iss3/17