Patients with renal calculi between 1 - 2 cm in diameter who were admitted to a tertiary health institution were evaluated prospectively. Patients who were unsuitable for shock wave lithotripsy (SWL) treatment or who did not benefit from SWL sessions were included in the study. Randomization was performed using a random number table with a central computerized system. Before the procedure, the patients were asked to complete the Turkish language validated form of the Short Form - 36 (SF - 36) questionnaire.

A total of 48 patients in whom ureteral access sheath insertion has failed during initial flexible ureterorenoscopy (f-URS) session were randomly divided into 2 groups. Group 1 underwent a JJ stent insertion and procedure terminated, while group 2 underwent mini percutaneous nephrolithotomy (mPNL) operation in the same session after prone positioning. Group 1 underwent f-URS 4-6 weeks later. One month after the operation, stone-free status was evaluated with computed tomography (CT) and detection of residual fragments of any size was defined as failure. The patients were asked to fill out the SF-36 questionnaire one month after the last surgery. Operative and postoperative data, SF-36 results, success, and complications were compared between the groups. The operation time included the time from initiation of cystoscopy to removal of amplatz for the mPNL group. For the F-URS group, it was calculated as the sum of the times between cystoscopy and fluoroscopy control of the JJ stent in both sessions.

Surgical technique All surgeries were performed by the same team of experienced surgeons in with high expertise in endourology. A guidewire was placed in the ureter in the lithotomy position. Ureterorenoscopy was performed with an 8 Fr ureterorenoscope for active dilatation. An 11 - 13 Fr or 9.5 / 11.5 Fr UAS was attempted to be placed under fluoroscopy by the surgeon of the procedure. In cases where the UAS could not inserted, a 26 cm, 4.8 Fr JJ stent was placed under fluoroscopy in the f-URS group, and the procedure was terminated. In the mPNL group, same session mPNL procedure was performed.

After initial JJ stent placement, patients in group 1 underwent a second f-URS session, 4 - 6 weeks later. After the JJ stent was removed, an 11 - 13 Fr UAS was placed in the ureter. Digital flexible ureterorenoscope was used as the flexible ureteroscope. Stone fragmentation was performed in dusting mode using a Ho:YAG laser with a 272 µ probe. After fragmentation, a 26 cm 4.8 Fr JJ stent was inserted into the ureter. The JJ stent was removed at 4 - 6 weeks postoperatively.

For patients in group 2, after placing a 5 Fr ureteral open-ended catheter, patients were positioned in prone position and access was performed to the appropriate calyx with an 18-gauge percutaneous access needle using the triangulation technique accompanied by fluoroscopy, in the first session. After the guidewire was introduced into the pelvicalyceal system, sequential dilatation was applied with Amplatz dilatators, and a 21 Fr metallic sheath was placed. Stones were fragmented with a yttrium-aluminum-garnet (Ho:YAG) Laser lithotripter. At the end of the procedure, a 14 Fr nephrostomy catheter was placed in according to the residual stone, hemorrhage, and perforation status. In other cases, the procedure was concluded as totally tubeless. Postoperative routine intravenous analgesia was not applied to all patients.

Study sample size analysis was computed using the G\*Power program (effect size 0.5, alfa error 0.05, power 0.80). Statistical analysis was performed with 'Statistical Package for the Social Sciences' (SPSS) 25 program. The normality assessment of the distribution of the data was analyzed with the Shapiro-Wilk test and Q - Q plot. For continuous covariates, normality and homogeneity of each variable were evaluated and Student's or Welch's t-test was performed. Mann - Whitney U test was used for skewed data. Quantitative data were presented as mean ± standard deviation or median (IQR) values. Chi-square test or Fisher exact test (where the 20% of expected cell counts were less than 5) was used to compare qualitative data. The normality of the differences in SF - 36 data before and after the procedure was evaluated with the Skewness test and Q - Q plot. Paired-sample t - test was used to compare SF - 36 data before and after the procedure. The data were analyzed at 95% confidence level and the values with P \< .05 were noted statistically significant.