Objectives. To establish the characteristics of mechanical activity during ureteral peristalsis and unidirectional bolus transport, pressure changes in the middle and distal (juxtavesical and ureterovesical junction) porcine ureter were quantified in vivo.

Methods. Five female New Yorkshire pigs (50 to 60 kg) were studied under halothane anesthesia. The endoscopic approach was used to position an 8-channel 6F perfusion catheter under direct vision into the distal ureter by way of the orifice. Ureteral activity was studied in two separate sessions at 1-week intervals. The pressure, propagation velocity, and length of the peristaltic waves were analyzed.

Results. The average maximal pressure in a not previously instrumented ureter amounted to 35.7 ± 1.2 cm H₂O in the mid-ureter, and decreased to 19.4 ± 1.3 cm H₂O in the juxtavesical ureter (P <0.001) and further to 7.2 ± 1.0 cm H₂O (P <0.001) in the submucosal segment. The propagation velocity of the peristaltic wave through the ureter was 2.1 ± 1.3 cm/s. The length of the pressure peak was 5.9 ± 1.6 cm.

Conclusions. A ureteral peristaltic contraction wave travels at approximately 2 cm/s and is approximately 6 cm long. It is responsible for the unidirectional transport of a urinary bolus and itself acts as an “active” antireflux mechanism. The maximal pressure in the lumen of the ureter decreased from proximally to distally, but remains sufficiently high at the ureterovesical junction to prevent retrograde urine leakage when the ureter empties its urinary bolus into the bladder and the orifice is open.