AB059. A novel technique of suctioning flexible ureteroscopy with automatic control of renal pelvic pressure

Objective: Flexible ureteroscopy is rapidly becoming a first line therapy for many patients with renal and ureteral calculi. Currently the medical infusion devices cannot monitor the renal pelvic pressure. We introduce a novel technique of flexible ureteroscopy with a suction system to treat upper urinary calculi and automatically control renal pelvic pressure.

Methods: We performed flexible URSs for patients with the help of a self-designed intelligent system including an irrigation and suctioning platform and a transparent ureteral access sheath (UAS) with a pressure-sensitive tip, which can precisely regulate the infusion flow and control the vacuum suctioning by computerized real-time recording and monitoring of RPP through pressure feedback, ensuring a stable RPP. The outer body diameter of the UAS was 15 F; the diameter of the working channel was 11.55 F; 
the length of the UAS was 20-45 cm. On the platform, RPP control value was set at −2 mmHg, RPP warning value was set at 20 mmHg, and RPP limit value was set at 30 mmHg. Intraoperatively, holmium laser was used to powderize the stone at 0.8 J/pulse with a frequency of 20 pulses/s (Lumenis, fiber diameter 200 um). In the process of powderizing lithotripsy using the laser, the scope body was moved back and forth slightly in an uninterrupted fashion in the sheath, with a distance of about 2-3 mm, to facilitate small gravel particles inside the sheath gap to be sucked out automatically. Gravel particles larger than sheath gap but less than UAS in diameter were sucked out by withdrawing the scope intermittently without a need of stone basketing. We retrospectively reviewed 37 patients with renal or ureteral calculus received the flexible URS from November 2014 to January 2015.

Results: The procedure was successfully performed in all patients with a clear operating field view. The mean stone size was 15.9±5.2 mm (rang: 8-35 mm). The mean operative time was 24.8±15.9 [13-49] min. The stone-free rates at postoperative day one and day 30 were 89.2% (33/37) and 94.6% (35/37), respectively. Complications were noted in 3 (8.1%) cases according to the Clavien classification, including systemic inflammatory response syndrome (SIRS) (grade I) in one case (2.7%), and fever (grade I) in two cases (5.4%). No sepsis occurred.

Conclusions: The technology is safe, and efficacious for treating upper urinary calculi with advantages breaking stones more effectively and low complication rates because of automatically of controlling renal pelvic pressure.

Keywords: Urinary calculi; renal pelvic pressure; pressure feedback