Minimally Invasive Percutaneous Nephrolithotomy (MIP): Initial North American Experience.

INTRODUCTION AND OBJECTIVES The goal of this study is to evaluate the outcomes in a cohort of patients who underwent MIP at a single institution from 2017 - 2019. METHODS 60 patients at a single institution with two different surgeons underwent MIP from 2017 to 2019. The MIP technique uses a proprietary nephroscope with a "vacuum" technique for stone evacuation.. Patients were identified who had post-operative computed tomography (CT) scan imaging available for direct review. A prospectively maintained database was queried along with retrospective chart review to evaluate the stone-free rate defined as no stones on CT imaging. Pre-op, intra-op and post-op variables were analyzed including initial stone size, access type (fluoroscopic vs ultrasonic), access location, operative positioning (supine vs prone), operative time, and 60-day complications. RESULTS 46 of 60 patients had CT imaging post-operatively that were reviewable. Of these, 43% (n=20) were stone free as defined by no identifiable fragments seen, 11% (n=5) had residual fragments 0-2mm, 7% (n=3) had residual fragments 2-4mm and 39% (n=18) had residual fragments greater than 4mm. Mean initial stone size was 21mm (1.9mm - 84mm). 60% (n=28) of the patients were discharged the same day as surgery (POD0). 51% (n=24) of access was achieved via ultrasound alone. 17% of patients (n=8) had a complication within 30 days of surgery. All complications were Clavien III or lower with unplanned return to OR rate of 2% (n=1). CONCLUSIONS We present North America's first single institution analysis of MIP cases with acceptable outcomes comparable to both RIRS and standard PCNL. The exact role of MIP in renal stone disease needs to be determined by future studies which critically assess their outcomes.