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

Volume 10, Issue 1

Review Article / Published: July 2022


О. Gatsev, V. Todorova, K. Hristov, P. Petrov, K.Petkova, I.Saltirov

Department of Urology and Nephrology, Military Medical Academy, Sofia, Bulgaria


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 unfavorable 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, unfavorable anatomy, and considerable costs for consumables represent limiting factors for this technique. With the miniaturization of the percutaneous approach and decreasing the morbidity, minimally invasive percutaneous nephrolithotomy (mini-PCNL) is a promising method for the 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 Endourology and SWL, Military Medical Academy, Sofia between January 2020 to January 2022, were retrospectively reviewed. All patients underwent mini-PCNL under spinal anesthesia in a prone position with fluoroscopic guidance through 18 Fr sheath using a semirigid nephroscope and Ho: YAG laser for lithotripsy. The stone-free rate was defined as the absence of residual fragments ≥2 mm. Data on patients’ preoperative characteristics, stone-free rates, operating times, and intra- and postoperative complications were analyzed.

Results: Patients’ mean age was 54,68±11,99 years. The mean stone surface was 169,02±57,40mm2 and the mean CT stone density was 1112,26±250,47 HU. Stone-free rate after a single procedure was 96,3 % (52 patients). 14,8% of patients had preoperative urinary tract infections. The mean operative time was 27,46±12,40 min and the 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 an intraoperative hemorrhage 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 the 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 unfavorable for SWL and RIRS.

Results: The comparative analysis of the preoperative characteristics of both groups did not reveal significant statistical differences. There were comparatively similar indicators for surgical intervention and regional anesthesia in both groups. Both anesthesia techniques showed a safety profile with hemodynamic stability, without additional medicine administration and lack of early post-anesthesia complications. The pain did not occur during insertion and moving the US probe into the anal canal and puncturing the perineal skin and the underlying tissues. 50% (3) of the patients in Group 2 had pain during the puncture of the prostate gland and biopsy extraction, while in Group 1 – 0% (0) of the patients reported the presence of pain. There was a slightly delayed onset of the first postoperative pain in Group 1 – 113.17 ± 15.11 min. compared to Group 2 – 99.83 ± 11.51 min. Conclusion: The saddle block anesthesia with 20 mg prilocaine hydrochloride 2% hyperbaric solution in combination with intravenous fentanyl at a dose of 1 mcg/kg is a safe anesthesia technique, associated with an excellent analgesic profile, low incidence of anesthesia-related complications and rapid recovery in patients undergoing MRI/US-TPB.


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Click to review Volume 10, Issue 1


minimally invasive nephrolithotomy, lower pole kidney, urolithiasis

How to cite this article:

Gatsev О, Todorova V, Hristov K,  Petrov P, Petkova K, Saltirov I. Efficacy and safety of minimally invasive percutaneous nephrolithotomy in patients with lower pole kidney stones 1-2 cm in diameter. Journal of Endourology and Minimally Invasive Surgery (Bulgaria), 2022; 10(1):25-32

Corresponding author:

Dr. Ognyan Gatsev

Department of Urology and Nephrology; Military Medical Academy Sofia

Address: Blvd“ Georgi Sofiiski” 6; Sofia-1606, Bulgaria

E-mail: gatsev @