Mechanism of trigonal influence on ureter during bladder filling and voiding An experimental study in dogs

The role of the trigone and the mechanisms involved in its influence on the ureteral activity during bladder filling and voiding were investigated in 5 groups of adult mongrel dogs. The study included an evaluation of the influence of nontrigonal factors. Stimulation of the trigone with electric current and induced voiding was performed and the activity in the ureters in which linear vents were created proximal to the ureterovesical junction was monitored. Trigonal electromyography supplemented the studies. The results indicated that nontrigonal intravesical factors additionally operated on the ureter. The mechanism of the trigonal influence on the ureter was twofold. It produced maximal response at the ureterotrigonal junction causing obstruction at the terminal segment of the intravesical ureter. Second, the trigonal activity propagated proximally into the adjacent ureter, which thereby exhibited a direct smooth muscle response. Electromyographic studies of the trigone revealed increased spike activity even during nonvoiding stage of passive bladder filling.