Efficacy and safety of minimally invasive percutaneous nephrolithotomy in patients with lower pole kidney stones 1-2 cm in diameter

Abstract

Introduction: Anatomical features of the lower pole calyces plays an important role in the treatment of urolithiasis. The optimal treatment options for lower pole stones with a diameter below 2 cm are controversially discussed. Extracorporeal shock wave lithotripsy (SWL) is non-invasive, but is hampered by low stone-free rates and a significant retreatment rate in patients with unfavourable factors for lithotripsy. Retrograde intrarenal surgery (RIRS) has been demonstrated to have high stone-free rates since the development of modern flexible endoscopes. But the long operative time in the case of a large stone burden, unfavourable anatomy and considerable costs for consumables represent limiting factors for this technique. With the miniaturization of percutaneous approach and decreasing the morbidity, minimally invasive percutaneous nephrolithotomy (miniPCNL) is a promising method for treatment of lower pole stones in one stage procedure. The objective of this study is to investigate the efficacy and safety of mini-PCNL for the treatment of lower pole stones 1-2 cm. Material and methods: The medical records of 54 patients with lower pole kidney stones 1-2 cm, treated at the Clinic of Endurology and SWL, Military Medical Academy, Sofia between January 2020 to January 2022, were retrospectively reviewed. All patients underwent mini-PCNL under spinal anesthesia in prone position with fluoroscopic guidance through 18 Fr sheath using semirigid nephroscope and Ho:YAG laser for lithotripsy. Stone-free rate was defined as absence of residual fragments ≥2 mm. Data on patients’ preoperative characterstics, stone-free rates, operating times, intra- and postoperative complications were analyzed. Results: Patients mean age was 54,68±11,99 years. Mean stone surface was 169,02±57,40mm2 and mean CT stone density was 1112,26±250,47 HU. Stone-free rate after single procedure was 96,3 % (52 patients). 14,8% of patients had preoperative urinary tract infection. Mean operative time was 27,46±12,40 min and mean hospital stay - 2,5±1,17 days. The mean Hgb drop was 11.9±15.6 g/l. Lower pole puncture was performed in all patients. Two tracts were required in 1 (1,9 %) patient. One patient had intraoperative haemorrhage at the end of the procedure. Postoperative complications were observed in 2 (3,8 %) patients: postoperative fever t >38.5o C in 1 patient (1,9%) and postoperative AV-fistula in 1 (1,9%) patient, who needed hemotransfusion and selective embolization. 2 patients required auxiliary procedures: 1 patient needed stent JJ and 1 underwent ureteroscopy for fragments in ureter. Conclusion: Various factors are important for management of lower pole kidney stones and should be taken into consideration, when choosing the optimal treatment modality. The results from this study suggest that mini-PCNL is an effective and safe procedure with high stone free rates and low complication rates in patients with lower pole kidney stones unfavourable for SWL and RIRS. Key words: minimally invasive nephrolithotomy, lower pole kidney, urolithiasis