Relocation of big stone fragments with direct-in scope suction.

Purpose: To investigate the effectiveness of DISS feature of novel 7.5Fr and 9.2Fr single-use flexible digital ureteroscopes to relocate and evacuate stone fragments (2-5 mm in diameter) without any accessory instruments.

Methods: An ex-vivo experimental study on porcine kidney and ureter was performed. Natural calcium oxalate dihydrate stone fragments sized 2-5 mm placed in the upper, middle and lower calyces were used. For each stone in each location 5 attempts were performed. The attempt was defined as successful if stone evacuation was reported while withdrawing the scope through the 12/14Fr UAS. The time collapsing the collecting system was also reported.

Results: The time needed to collapse the porcine pelvi-calyceal system (PCS) was 4-5 s for 9.2Fr and 5-6 s for 7.5Fr scope. Evacuation of 2 mm stone fragments occurred in all trials both with 9.2Fr and 7.5Fr scopes. In case of 3 mm stone, evacuation of stone fragments was observed in 3 out of 5 and 1 out of 5 attempts in upper calyx, 5 out of 5 and 3 out of 5 in the middle calyx and 2 out of 5 and 0 out 5 in lower calyx using 7.5Fr and 9.2Fr scope, respectively.

Conclusion: The DISS feature of the novel 7.5Fr and 9.2Fr single-use digital flexible ureteroscope can be potentially used not only to aspirate dust but also to relocate and evacuate larger stone fragments up to 4 mm in diameter using only suction. The speed of collapse of the PCS seems to be one of the main predictors of success.