A novel small fragment removal system holds promise to improve stone extraction during lithotripsy

To describe a novel small fragment removal system (SFRS) which is hypothesized to improve kidney stone fragment removal during laser lithotrypsy. The SFRS consists of three parts: a Syphon Ureteric Access Sheath (SUAS), a Dual Action Pump (DAP) and an Agitator. This clinical trial aims to assess the SFRS's impact on intra-renal pressure (IRP) and irrigant flow rate compared to a traditional UAS and its stone fragment removal capabilities.

Patients who met the inclusion criteria were enrolled in this prospective single arm seamless Phase 1 and 2 clinical trial. The primary objective of Phase 1 was to evaluate the safety of the SFRS in terms of IRP changes. In Phase 2 we attempted to evaluate the device's efficacy in removing stone fragments. During standard laser lithotripsy, the DAP and Syphon UAS were compared to a conventional UAS in terms of irrigant flow and IRP at baseline and during fluid bolus administration. Additionally, the percentage of stone fragments removed using the SFRS with the Agitator introduced (in place of the fURS) was assessed.

Twelve (n = 12) patients were enrolled. The SFRS showed lower baseline IRP - 20,8 vs. 24,6mmHg for the traditional UAS (p = 0,004). During fluid boluses the IRP was lower for the SFRS at 23,5 vs. 75,2mmHg (p = 0,0002). Greater irrigant flow was seen with the SFRS of 39,2 vs. 34,9mL/min (p = 0.002). Mean pre-op stone volume was 238mm³ (range 70-562 mm³), compared to 1,4mm³ post-op (range 0-8mm³).

The novel SFRS holds clinical promise to improve patient safety by reducing IRP with a significant reduction in IRP during fluid bolus administration. It also has the potential to improve visibility via a significant increase in irrigant flow. Lastly, the SFRS was able to remove the overwhelming majority of stone fragments. The main limitation of the study is the small sample size.