In Vitro Evaluation of Stone Fragment Evacuation by Suction

Contemporary, flexible stone baskets are unable to extract submillimeter stone fragments at the time of ureteroscopic laser lithotripsy. In this in vitro study, the feasibility of suctioning submillimeter fragments with a standard Luer Lock syringe through the working channel of a flexible ureteroscope was assessed. Phantom stones made from industrial plaster were mechanically fragmented into ≤1 and ≤0.5-mm groups. Both stone groups were divided into five preweighed trial samples. Each stone group was then mixed in a beaker filled with normal saline. A standard 10-mL Luer Lock syringe was connected to a fiber-optic ureteroscope with a 1.2-mm working channel. The syringe was then used to suction stone fragments from the beaker. The suctioned stone fragments and the stone fragments remaining in the beaker after removing the overlying solution were separated, centrifuged with supernatant removed, and dried in an incubator set at 33°C for 1 week. Dried weights were recorded. Mean total weights for ≤0.5 and ≤1.0-mm stone groups at baseline were 0.807 and 0.806 g, respectively. The mean percentages of stone fragments suctioned through the ureteroscope for ≤0.5 and ≤1.0-mm groups were 86% and 86%, respectively (p = 0.973). During suctioning, 64% of stones in the ≤0.5-mm group were trapped in either the working channel of the ureteroscope or within the Luer Lock syringe compared with 78% of stones in the ≤1-mm group (p = 0.001) requiring cessation of the procedure to clear the channel. It is feasible to suction submillimeter stone fragments by connecting a Luer Lock syringe to the working channel of a flexible ureteroscope. The limiting factor for removing stone fragments appears to be the small working channel of flexible ureteroscopes as trapping of fragments during suctioning is common and requires time-consuming removal of the endoscope and clearing of the channel.