Minimally Invasive Percutaneous Nephrolithotomy: Initial North American Experience

Introduction and Objectives: The goal of this study is to evaluate the outcomes in a cohort of patients who underwent minimally invasive percutaneous nephrolithotomy (MIP) at a single institution from 2017 to 2019. Methods: Sixty 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 postoperative 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. Preoperative, intraoperative, and postoperative 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: Forty-six of 60 patients had CT imaging postoperatively 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 to 2 mm, 7% (n = 3) had residual fragments 2 to 4 mm, and 39% (n = 18) had residual fragments >4 mm. Mean initial stone size was 21 mm (1.9-84 mm). Sixty percent (n = 28) of the patients were discharged the same day as surgery. Fifty-one percent (n = 24) of access was achieved through ultrasound alone. Seventeen percent of patients (n = 8) had a complication within 30 days of surgery. All complications were Clavien III or lower with unplanned return to operating room rate of 2% (n = 1). Conclusions: We present North America's first single institution analysis of MIP cases with acceptable outcomes comparable with both retrograde intrarenal surgery and standard percutaneous nephrolithotomy. The exact role of MIP in renal stone disease needs to be determined by future studies that critically assess their outcomes.