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A Novel Device to Prevent Stone Fragment Migration During Percutaneous Lithotripsy: Results from an In Vitro Kidney Model.

PURPOSE
We developed a polyethylene sack (the PercSac) that fits over the shaft of a rigid nephroscope and is deployed into the collecting system to capture a stone and contain fragments during percutaneous nephrolithotomy (PCNL). We previously reported our results using the PercSac in a percutaneous cystolithopaxy model. In this study, we compare the efficiency of stone fragmentation with and without the PercSac in an anatomically correct in vitro PCNL model.


MATERIALS AND METHODS
The PCNL model consisted of a human collecting system model created on a 3D printer. Ten BegoStones made in spherical molds of 2.0 cm diameter, matched for weight, were fragmented in the model using a 24F rigid nephroscope and an ultrasonic lithotripter, including five with and five without the PercSac. The total times for stone fragmentation and complete stone clearance, gross assessment of the stone-free status, and need for flexible nephroscopy to achieve a stone-free state were recorded.


RESULTS
The median time for stone fragmentation was significantly shorter in the PercSac group compared with the control group (217 seconds [IQR = 169-255] vs 340 seconds [IQR = 310-356], [p = 0.028]). Likewise, the total time for complete stone clearance from the kidney was significantly shorter for the PercSac group (293 seconds [IQR = 244-347] vs 376 seconds [IQR = 375-480], [p = 0.047]). In one trial with the PercSac, residual dust remained in the kidney, while in all five trials without the PercSac small residual fragments remained. All trials without the PercSac required flexible nephroscopy with basket extraction to become stone free, while none of the trials with the PercSac required flexible nephroscopy for stone clearance.


CONCLUSIONS
Ultrasonic lithotripsy using the novel PercSac stone entrapment device is more efficient and efficacious than traditional ultrasonic lithotripsy in an in vitro PCNL model. The advantage may be even more pronounced during clinical PCNL where residual fragments migrate into difficult-to-access calices. Further in vivo testing is underway.