Introduction. Today it is urgent to introduce into clinical practice more advanced methods of kidney stone treatment with high indicators of their effectiveness and safety while minimizing the risk of repeated interventions. The goal of effective treatment of kidney stones is to completely rid the patient of stones and complaints, to eliminate organ dysfunction, using minimally invasive treatment methods that reduce the patient’s hospital stay and the risk of complications. However, there are only few studies comparing the clinical efficacy and safety of modern methods of surgical treatment of kidney stones 2 to 3 cm in size. Remote shockwave lithotripsy or retrograde intrarenal surgery is the treatment of choice for kidney stones up to 2 cm, and percutaneous nephrolithotomy is the treatment of choice for stones larger than 2 cm. Flexible ureterorenoscopy is not recommended as first-line treatment in patients with kidney stones >2 cm due to the high risk of reintervention, according to the RTC clinical guidelines. However, it can be performed successfully in centers with extensive experience with this technique. The advantages of retrograde intrarenal surgery are low trauma, low risk of complications such as bleeding and damage to adjacent organs, and shorter hospital stay. The efficacy of flexible ureterorenoscopy is significantly lower for stones larger than 3 cm, and for stones between 2 and 3 cm there are only a few studies, which do not allow a reliable judgment on the efficacy and safety of this technique.
Purpose of the study. To evaluate the efficacy and safety of flexible ureterorenoscopy in comparison with mini-percutaneous nephrolithotomy for kidney stones from 2 to 3 cm.
Materials and methods. A prospective randomized study to determine the efficacy of methods of surgical treatment of kidney stones from 2 to 3 cm in size using flexible ureterorenoscopy and mini-PCNL was conducted at the Institute of Urology and Human Reproductive Health of the I.M. Sechenov First Moscow State Medical University (Sechenov University) in Moscow. The study analyzed the results of the performed surgical interventions in patients with urolithiasis using flexible URS and mini-PCNL as an example from the point of view of their effectiveness and safety for kidney stones from 2 to 3 cm.
The study utilized the results of 133 patients (including 64 patients after flexible URS and 69 patients after mini-PCNL). The mean size and mean density and location of the nodule between the groups were comparable and had no statistically significant differences.
The effectiveness of the intervention in the form of complete absence of concretions, length of stay in the clinic, operative time, development of postoperative complications (bleeding, urinary tract infection) and Clavien’s surgical complication score were evaluated.
Results of the study. The duration of surgery was longer in the flexible URS group where it amounted to 69.9±9.3 minutes, in the mini-PCNL group the duration of surgery averaged 48.3±5.8 minutes (p=0.0001).
The incidence of early postoperative complications in the flexible URS group was 6,2%, in the mini-PCNL group – 12,6%, which had statistically significant differences between the study groups at the level of p=0.001.
The length of stay in the clinic was shorter in the flexible URS group, which averaged 2±1 days, while in the mini-PCNL group the length of stay was 5±2 days (p=0.0003).
The frequency of concrement removal 3 months after the surgical intervention detected by computed tomography in the group of flexible URS was lower and amounted to 90,6%, in the group of mini-PCNL this index was at the level of 92,7% (p=0,06).
Conclusion. The results of this study demonstrate that flexible URS and mini-PCNL have a comparable success rate in removing concretions. Flexible URS reduces hospitalization time, causes fewer complications and can be used as an alternative in the treatment of kidney stones from 2 to 3 cm. Meanwhile, mini-PCNL has shown a higher percentage of effectiveness in getting rid of concretions 3 months after surgical intervention.

Keywords: mini-percutaneous nephrolithotripsy, flexible ureterorenoscopy, kidney stones, urolithiasis