Ureterovesical junction inhibitory reflex and vesicoureteral junction excitatory reflex: description of two reflexes and their role in the ureteric antireflux mechanism.

The purpose of this study was to investigate the response of the ureterovesical junction (UVJ) to ureteric distension and to bladder filling with the aim of elucidating the mechanism of UVJ antireflux. The study was performed on 13 healthy volunteers [age 41.4 +/- 10.2 (SD) years; nine men, four women]. A ureteric catheter connected to a pressure transducer was introduced into the ureter proper. After recording the ureteric pressure, the catheter was withdrawn to the bladder, and the resting pressures in the UVJ and bladder were registered. The catheter was positioned in the UVJ and a 3F balloon-tipped ureteric catheter was introduced into the ureter proper and filled saline in increments of 1 ml. The pressure response of the ureter and UVJ to ureteric distension was recorded. The bladder was then filled with 400 ml saline at two rates, slow (10 ml/min) and rapid (150 ml/min), and UVJ pressure response was registered. The aforementioned tests were repeated after anesthetizing the UVJ, the bladder musculature surrounding the UVJ and the ureteric wall at the site of the ureteric distension, respectively. Ureteric distension of the lower 2-3 cm effected ureteric pressure elevation (P < 0.05) and a UVJ pressure drop (P < 0.05); no pressure response of the UVJ occurred upon ureteric distension above this level. Slow bladder filling induced an increase in the UVJ (P < 0.01) and vesical (P < 0.01) pressures only when vesical filling reached a mean of 219.6 +/- 79.4 ml and above. Upon rapid vesical filling the pressure response occurred at a smaller volume (136.6 +/- 52.3 ml). The pressure response did not occur when the UVJ was anesthetized. The study showed that lower ureteric distension was associated with a UVJ pressure drop. This reflex relationship, which we call the "ureterovesical junction inhibitory reflex," was reproducible and disappeared on anesthetizing the UVJ or ureter. Vesical filling above a certain volume induced a UVJ pressure increase which was reproducible and disappeared on anesthetizing the UVJ; we call this reflex relationship the "vesicoureteral junction excitatory reflex." These two reflexes seem to regulate the entry of urine from the ureters to the bladder and prevent ureteric reflux during bladder filling. In conclusion, two reflexes are identified that might contribute to the mechanism of UVJ antireflux.