Effect of renal pelvic distension on the ureteropelvic and ureterovesical junctions and the urinary bladder: the renal pelvivesical reflex.

For investigation of the effect of distension of the renal pelvis on the ureteropelvic (UPJ) and ureterovesical junctions (UVJ) and on the urinary bladder, nephrostomy was performed on 14 anesthetized mongrel dogs. The pressure was measured in the UPJ by a catheter with a side port introduced through the nephrostomy and in the UVJ and urinary bladder by two catheters inserted cystoscopically. Likewise, a balloon mounted on the tip of a catheter was introduced into the renal pelvis. It was filled with saline in increments of 1 ml, and the pressure response of the UPJ, the UVJ, and the urinary bladder was determined. The test was repeated on the anesthetized renal pelvis, UVJ, and bladder. Whereas renal pelvic distension with 1 ml of saline effected no pressure response in the UPJ, UVJ or bladder, distension with 2-4 ml produced a significant pressure drop (P < 0.01, P < 0.01, and P < 0.05. respectively). There was no difference in the pressure drops recorded at distensions with 2, 3, or 4 ml of saline (P > 0.05). Distension of the anesthetized renal pelvis produced no pressure response in the UPJ, UVJ, or bladder. Furthermore, renal pelvic distension did not elicit a pressure response in the anesthetized UPJ or the bladder. In conclusion, the opening of the UVJ synchronously with the UPJ upon renal pelvic distension appears to assist the delivery of urine from the renal pelvis to the urinary bladder and to protect both the renal pelvis and the ureter against dilatation. This process is supported by a vesical pressure drop. The opening of the UPJ together with the UVJ and the vesical relaxation observed on renal pelvic distension seem to be reflex in nature. A "renal pelvivesical reflex" is postulated to regulate the flow of urine from the renal pelvis to the urinary bladder, preventing the occurrence of urine collection in, or backflow into, the renal pelvis or the ureter.