Mini Percutaneous Nephrolithotomy for Large Complex Stones: Role of Ultrasound

Mini percutaneous nephrolithotomy (mPCNL) offers an effective approach for treating large renal stones, particularly when enhanced by vacuum-assisted access sheaths, which aid in retrieving larger stone fragments. This study aimed to establish an optimal linear stone burden cutoff value that could predict stone-free rates (SFR) after mPCNL. Using an ultrasound-guided technique, the procedure begins with the patient in a prone position, where a percutaneous access tract is dilated to 14 Fr, followed by the insertion of a 16/18 Fr vacuum-assisted access sheath. Nephroscopy is conducted using a 12 Fr mini nephroscope, with stone fragmentation performed using a 365 µm thulium fiber laser. Stone dust is efficiently removed through the sheath, and larger fragments are actively suctioned out by manipulating the scope and adjusting suction strength. In this retrospective review of mPCNL cases for stones larger than 2 cm conducted between November 2021 and June 2023, 74 patients were included. The mean linear stone burden was 42.1 mm, with a significant number of patients (77%) being discharged on the same day. The overall SFR was 63.5%, and a ROC curve analysis revealed that a linear stone burden cutoff of 40.3 mm provided a sensitivity of 73.1% and specificity of 70.2%. Notably, SFR below this threshold was 82.5%, compared to 42.2% for those above it, emphasizing the importance of stone burden in achieving successful outcomes. These findings indicate that mPCNL is a promising option for managing large and complex stones, especially when utilizing new technologies that facilitate improved surgical results.