Impact of a double-pigtail stent on ureteral peristalsis in the porcine model: Initial studies using a novel implantable magnetic sensor

Background and Purpose: The effect of stents on ureteral peristalsis in vivo is not entirely clear. We sought to develop a minimally invasive method for its study. Materials and Methods: In female domestic pigs, electrical potentials from the ureter were measured by bipolar steel-wire electromyography electrodes delivered laparoscopically. Mechanical movement was measured by giant magneto resistive sensors mounted on custom-made aluminum strips. After baseline values were obtained, the animals were randomized to receive silicone or polyurethane stents, and ureteral peristalsis was measured for 8 hours acutely and for 4 hours 1 week later. Results: Implantation of the devices took an average of 30 minutes. A consistent correlation was found between laparoscopically observed peristaltic waves and the peristalsis detected by the two measuring devices. The devices themselves did not affect peristalsis. Stent insertion increased peristaltic activity initially but later reduced or stopped it. There was no difference in the effects of the two types of stents. Conclusions: The new technique permits close monitoring of ureteral peristalsis in vivo. Smaller stents appear to have less immediate effect than larger ones, but all type of stents tested eventually caused aperistalsis.