Optimizing suction force in RIRS with DISS system: an experimental ex-vivo study

BACKGROUND: The aim of this study was to investigate various suction force parameters to improve stone relocation and prevent pelvi-calyceal system (PCS) collapse.METHODS: An experimental ex-vivo study was performed using a freshly harvested porcine upper urinary system. Flexible ureterorenoscopy was performed using two novel 7.5-Fr (PU3033AH) and 9.2-Fr (PU400A) (Pusen, ZhuHai Pusen Medical Technology Co, Ltd, Guangdong, China) digital single-use flexible ureteroscopes. Natural stone fragments (calcium oxalate dihydrate) of 2-4 mm in size were used. The stone fragments were used to evaluate stone relocation using suction (SRS). The trial was successful if the stone fragment was relocated to the renal pelvis from either pole. Suction settings were set at 50 mmHg, 100 mmHg, and 150 mmHg.RESULTS: The PCS collapse times were 10, 7, and 5 seconds for the 7.5-Fr scope, and 7, 5, and 3 seconds for the 9.2-Fr scope. A higher SRS success rate was seen with 2-mm fragments. Using a 7.5-Fr DISS scope, 100% success occurred at suction settings of 150 mmHg and 100 mmHg, but only 33.3% at 50 mmHg. Similarly, with a 9.2-Fr scope, better outcomes were observed for 2-mm stones compared to 3-mm and 4-mm stones. The 100-mmHg suction setting achieved an 83.3% success rate for 2-mm stones. Adjusting the suction worsened the success rate, resulting in 16.7% or one successful SRS in six trials for 2-mm stones.CONCLUSIONS: The 9.2-Fr DISS ureteroscope, equipped with a larger 5.1-Fr working channel, demonstrated faster collapse of the PCS across all suction settings in comparison to the 7.5-Fr DISS scope. According to our study, the 100-mmHg suction force setting was linked to optimal stone relocation outcomes. Both the 7.5-Fr and 9.2-Fr DISS scopes experienced similar effects when the suction force was reduced to 50 mmHg. However, an increased suction force to 150 mmHg resulted in a more significant deterioration of the SRS for the 9.2-Fr scope compared to the 7.5-Fr scope.