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INTRODUCTION: There are conflicting results in the literature regarding the efficacy of Retrograde intrarenal surgery (RIRS) in lower pole stones. This study aimed to evaluate RIRS outcomes in lower pole stones by forming matched case-control groups. METHODS: The data of 491 patients who were diagnosed with kidney stones and underwent RIRS were retrospectively included in the study. A total of 209 patients with lower pole stones (Group 1) and 282 patients with pelvic stones (Group 2) were matched at a 1:1 ratio in terms of stone burden, stone density, preoperative double-J stenting status, and a previous history of shock wave lithotripsy, yielding 159 patients in each group. A computed tomography scan was performed to evaluate the stone-free status. The primary outcome was stone-free status one month after RIRS. RESULTS: After case-control matching, the median age was 49 years (interquartile range [IQR]: 40-58) in Group 1 and 50 years (IQR: 35-60) in Group 2 (p=0.388). The median stone burden values of Group 1 and Group 2 were 415.3 mm3 (IQR: 176.1-858.2) and 503.3 mm3 (IQR: 282.5-864), respectively (p=0.100). After RIRS, stone-free status was achieved by 126 of the 159 (79.2 %) in Group 1 and 133 of the 159 (83.6%) patients in Group 2 (p=0.387). The groups were similar in terms of perioperative complications (4.4% in Group 1 and 3.8% in Group 2, p=0.777), postoperative complications (13.8% in Group 1 and 10.3% in Group 2, p=0.393), and median operation time (60 min in both, p=0.230). A longer median fluoroscopy time was noted in Group 1 compared to Group 2 (26 sec and 3 sec, respectively, p=0.013). CONCLUSIONS: Stone-free rates and complications were comparable between the patients with lower pole and pelvic stones after RIRS. However, lower pole stones are associated with longer fluoroscopy time. RIRS can be performed effectively for the treatment of lower pole stones.

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A JJ stent placed before retrograde intrarenal surgery (RIRS) may ease the procedure. However, it is important to note that a prolonged duration of double J stent (DJS) placement before RIRS may increase the risk of postoperative urinary tract infection (UTI). Various publications have established this association, although the duration of the DJS before surgery is scarce. Our study investigates the relationship between the pre-stenting period and postoperative UTI and establishes a cut-off period to minimize this risk. We included a total of 500 cases with preoperative DJS prior to RIRS. The patients were divided into five groups according to their preoperative stenting duration (Group 1: 0-15 days; Group 2: 16-30 days; Group 3: 31-45 days; Group 4: 46-60 days; Group 5: >60 days). Demographic and clinical data of the patients, stone properties, operation data, perioperative and postoperative complications (including fever and UTI), hospitalization time, and stone-free rates (SFR) were compared. The groups contained 53, 124, 102, 63, and 158 patients. The demographics of the patients in each group were similar. There was no statistically significant difference between DJS duration, perioperative/postoperative complications, and SFR, except for the ureteral access sheath (UAS) insertion rate. (p = 0.001). The postoperative fever/UTI rate was the lowest in Group 1 (p = 0.046) compared to other durations. Stent duration does not impact SFR. Longer stents enhance UAS insertion success but increase postoperative infection risk. Our results suggest that RIRS should be performed within two weeks, ideally 20 days following stent insertion, to minimize postoperative infection risk.

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INTRODUCTION: The aim of the study was to evaluate the efficacy and safety of retrograde intrarenal surgery (RIRS) in elderly patients by comparing them with propensity score-matched age-groups. METHODS: Patients who underwent RIRS to treat upper urinary tract stone disease at seven centers were included in the study and were divided into four groups. The age intervals of the patients in group 1, group 2, group 3, and group 4 were 18-29 years old, 30-49 years old, 50-64 years old, and over 65 years old, respectively. Propensity score matching analysis was used to homogenize the groups in terms of demographic and clinical properties. Operative results, preoperative complications, perioperative complications, postoperative complications, duration of hospitalization time, and stone-free status were compared between groups. RESULTS: A total of 1,017 patients were included in the study. There were 69 (9.9%) patients in group 1, 324 (46.5%) in group 2, 217 (31.1%) in group 3, and 87 (12.5%) in group 4 after propensity score matching. The operation time and postoperative complication rates were significantly different among groups, whereas the hospitalization time, perioperative complication rates, and stone-free status were similar. The operation time was significantly higher in patients over 65 years old (p = 0.001). The postoperative complication rates were significantly higher in group 1 with Clavien I-II complication predominance (p = 0.003). CONCLUSION: The efficacy and safety of RIRS did not change with aging, and RIRS was an effective option for the treatment of upper urinary system stones in elderly patients.

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Purpose: Reusable flexible ureteroscopes may lose their mechanical functionality through overuse, which is known as "aging of the flexible ureteroscope." Although mechanical deterioration has been shown in several studies, the data about the effect of this situation on the efficacy and safety of retrograde intrarenal surgery (RIRS) are missing. The aim of our study was to evaluate the effect of the aging of flexible ureteroscopes on the efficacy and safety of RIRS. Methods: Patients who had undergone RIRS between 2017 and 2021 at a single center were retrospectively included in the study. Serial surgeries were performed using the same reusable flexible ureteroscope (Storz X2) until it was broken or malfunctioned because of the aging process. Group 1 was formed by the first 10 cases on whom the flexible ureteroscopes were used, representing the youngest period of the instruments, whereas group 2 was composed of the last 10 cases on whom the flexible ureteroscopes were used, representing the oldest phase of the instruments. The operative and postoperative data-including the operation time, hospitalization time, intraoperative complications, postoperative complications, and stone-free rates-were compared between the two groups. Results: A total of five flexible ureteroscopes were included in the study. The number of cases for each flexible ureteroscope ranged between 87 and 133, with a median number of 107 cases. The demographic and clinical properties of patients in both groups were similar. The operation time, lasering time, and total laser pulse were similar between the groups. The stone-free rates in group 1 and group 2 were 82.0% and 78.0%, respectively (p = 0.304). The complication rates were also similar between the groups (p = 0.591). Conclusion: The aging of reusable flexible ureteroscopes did not negatively affect the efficacy and safety of RIRS. Therefore, surgeons may use the reusable types of flexible ureteroscopes until they are totally broken.

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Objective: To investigate the association between psoas muscle mass (PMM) and failure of ureteral access sheath (UAS) insertion and complications from retrograde intrarenal surgery (RIRS). Materials and Methods: A multicenter retrospective case-control study was conducted that included patients who underwent RIRS despite failure of UAS insertion (Cohort 1) and confounder-matched control patients who underwent RIRS after successful UAS insertion (Cohort 2). For morphometric analysis of PMM, ipsilateral psoas muscle areas (iPMAs) were measured using the coreslicer.com webkit. After comparing demographic, clinical, and complication rates and iPMAs between cohorts, gender-specific median iPMAs were also determined to further subdivide patients in each cohort as either low iPMAs or high iPMAs. Thereafter, patients were also compared in terms of RIRS complications. Results: Cohort 1 included 86 patients whereas Cohort 2 consisted of 124 matched cases. The median (interquartile range) iPMAs were similar between the cohorts: Cohort 1, 11.05 (6.82-14.44) cm2 versus 11.12 (6.97-13.69) cm2 for Cohort 2 (P ˃ .05). There was a significant inverse relationship between iPMAs with age (r = -0.222) and Charlson comorbidity index (r = -0.180) for all patients (P ˂ .05). Perioperative and postoperative complication rates were 8.1% and 16.3% for Cohort 1 and 6.5% and 21% for Cohort 2, respectively. The complication rates were not statistically different between patients with high iPMAs and those with low iPMAs, in male or female patients (P > .05). Conclusions: These results show that failure of UAS was not associated with PMM. Furthermore, since the complication rates were similar between patients with high PMM and low PMM, RIRS may be a reliable treatment choice for sarcopenic patients as well as in nonsarcopenic patients.

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OBJECTIVE: To evaluate the sensitivity and specificity of ultrasonography (USG) and kidney ureter bladder radiography (KUB) for the determination of stone-free status of retrograde intrarenal surgery (RIRS) according to different stone-free status definitions. MATERIALS AND METHODS: The patients who underwent RIRS between September 2021 and September 2022 were prospectively included in the study. All patients underwent a KUB radiography, urinary system USG and noncontrast abdominal tomography at the postoperative first month of the surgery. The sensitivity, specificity, negative predictive factor, and positive predictive factor of USG and KUB on evaluating the stone-free rate were analyzed according to different stone-free status definitions. RESULTS: A total of 178 patients were included in the study. The stone-free rates according to stone-free definitions as; residual stone <4 mm, <2 mm and no residual stone were 79.2%, 64.0%, and 56.7%, respectively. According to its definition as a residual stone <4 mm, the sensitivity and specificity of USG were 64.9% and 84.3%, respectively. The sensitivity of USG was 57.1% and 52.5% as the definitions were residual stone <2 mm and no residual stone, respectively. Addition of KUB to USG slightly increased the sensitivity but did not change the specificity. CONCLUSION: USG had high specificity but low sensitivity for evaluating stone-free status after RIRS and addition of KUB did not increase the diagnostic efficacy. Although USG may be used in daily practice, it may overestimate the stone-free status and noncontrast abdominal tomography must be used during the clinical trials to document the exact stone-free rates of RIRS.

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Background: The aim of this study was (1) to explore effect of ureteral access sheath (UAS) use on primary retrograde intrarenal surgery (RIRS) outcomes, short-term kidney functions, radiation exposure, and ureteroscope lifetime (URS-LT) and (2) to reveal factors that predict UAS insertion failure. Materials and Methods: Patients (n = 1318) who underwent RIRS without UAS (Group 1), those who had operation with a <11-13 Fr (Group 2), and those with a ≥11-13 Fr UAS were matched (1:1:2) and compared. Stone-free rate (SFR), intra- and postoperative complications, acute kidney injury (AKI), fluoroscopy time, URS-LT, and UAS insertion failure were the outcomes. Results: SFR, which was highest in Group 3 (75%, 71% and 87.3%, respectively; P = .001), was significantly associated with use of ≥11-13 Fr (odds ratio [OR]: 4.2, P < .001), but was not with use of <11-13 Fr UAS (OR: 1.3, P = .3). Group 3 had less need for auxiliary procedure (15%, 16%, and 7.4%, respectively; P = .03). Five percent of patients had a risk of AKI, but only 0.3% developed AKI. Although UAS use was protective against creatinine increase (OR: 0.65, P = .02), increased risk of AKI was only associated with female gender (OR: 5.5, P < .001). Fluroscopy times were 5, 15, and 87 sn, respectively (P < .001). Short URS-LT was strongly associated with high frequency of lower calix stones (r = -0.94, P = .005), but URS-LT was not correlated with sheathless case rate (r = 0.59, P = .22). UAS insertion success in first attempt was more likely in younger (OR: 0.99, P = .03), hydronephrotic (OR: 3.4, P < .001), and female cases (OR: 1.5, P = .008). But absolute UAS insertion failure was associated with female gender (OR: 2.7, P = .017). Conclusions: Not any UAS use but a higher caliber UAS use may improve SFR and protect against AKI after RIRS. Although UAS insertion failure is seen mostly in men, it may be more challenging in women owing to less efficacy of preoperative Double-J stent.

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Background: The aim of this study was to evaluate the efficacy and safety of retrograde intrarenal surgery (RIRS) in patients with renal calculi with solitary kidneys (SKs). Materials and Methods: In this retrospective, multicenter study, a matched case-control study was carried out using the data from 522 RIRS patients treated between 2014 and 2021. Patients' demographic data, stone characteristics, operative outcomes, perioperative and postoperative complications, and surgical success were analyzed. All patients were evaluated with noncontrast-enhanced computed tomography (NCCT) preoperatively and 1 month after the surgery. Surgical success was defined as no evidence of remaining residual fragments of <3 mm in the first-month postoperative NCCT images. The case group of 29 patients with SKs (Group 1) treated with RIRS were matched with 76 control patients (Group 2) with bilateral kidneys, who underwent unilateral RIRS by propensity score-matched (PSM) analysis. Results: After PSM analysis, the demographic and clinical data did not differ significantly between the groups. The stone burden was similar between the groups: 733.6 mm3 (range: 50.4-7565.9) versus 991.1 mm3 (range: 201.2-4380.6) (P = .09), respectively. The perioperative complication rates were 13.8% (n = 4) in Group 1 and 11.8% (n = 9) in Group 2 (P = .78). There was no statistically significant difference between the groups for postoperative complication rates (minor complications, classified as Clavien 1 or 2), (6.9% [n = 2] versus 13.2% [n = 10; P = .34]), respectively. Surgical success was 82.8% (n = 24) in Group 1 and 83.6% in Group 2 (P = .92). There was no significant difference between preoperative and postoperative glomerular filtration rate and creatinine values (P = .005). Conclusions: Our results support that RIRS is a safe and effective treatment method in SK patients with similar complication and stone-free rates compared to patients who had bilateral functional kidneys and underwent unilateral RIRS.

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Horseshoe kidney is the most prevalent congenital kidney fusion anomaly, affecting 0.25% of the general population and occurring in 1 in 400-1600 births. Approximately 40 percent of patients develop kidney stones due to anomalies. In our case, we aimed to perform combined laparoscopic pyelolithotomy with retrograde intrarenal surgery (RIRS) instead of percutaneous nephrolithotomy (PNL) in a patient with a horseshoe anomaly. This procedure enabled us to detect the location of the mobile stone with RIRS and then successfully extract it with laparoscopic pyelolithotomy. Laparoscopic pyelolithotomy combined with RIRS is a reasonable additional treatment option for complicated stone surgery due to horseshoe kidney anomalies.

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INTRODUCTION: Although retrograde intrarenal surgery (RIRS) is being performed with increasing frequency, there are only a limited number of studies about the learning curve (LC). This study aimed to analyze the LC of RIRS for five surgeons who underwent the same training. MATERIALS AND METHODS: The data of the 410 patients who underwent RIRS between April 2017 and 2022 in a single institution, which were performed consecutively by five surgeons, were analyzed. All 50 cases performed by each surgeon were included and numbered consecutively and separately, according to the date of the operation. The combined stone-free rate (SFR) was calculated for each surgeon's cases in the same row, and the LCs were created using moving average and cumulative sum (CUSUM) analyses. Separate multivariable analyses identified each period's (LC vs. beyond) characteristics. RESULTS: The LCs from the combined SFRs reached a plateau after approximately 50 cases for both the CUSUM and the moving average. The effect of stone burden on SFR was more evident in the first 50 cases compared to subsequent cases in the multivariable analyses (p = 0.001 and p = 0.047, respectively). Case order and stone density were independent factors in the first 50 cases (OR: 1.02 [95% CI 1.00-1.04], p = 0.04 and OR: 0.99 [95% CI 0.99-1.00], p = 0.04) but not significant in subsequent cases (OR: 0.97 [95% CI 0.94-1.00], p = 0.1 and OR: 1.00 [95% CI 0.99-1.00], p = 0.7, respectively). Compared to single locations except the lower calyx, the unfavorable effect of the multiple-stone localization on SFR grew in strength after the 50th case (OR: 0.42 [95% CI 0.23-0.78], p = 0.01 and OR: 0.20 [95% CI 0.09-0.46], p < 0.001, respectively). CONCLUSIONS: This is the first study reporting on the RIRS LCs of urology residents. While stone burden, density, and multiple-stone localization were the factors determining SFR in the learning period, after completing the LC, the effect of stone burden weakened and multiple-stone localization became stronger.

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Urethral fibroepithelial polyps are uncommon benign tumors. The clinical presentation comprises of acute urinary retention, obstructive bladder symptoms such as frequent urination and urination difficulties, and hematuria. Usually, the diagnosis is made through the use of ultrasonography, voiding cystourethrography, and urethrocystoscopy. This study presents a case report of a four-year-old patient with urinary retention and frequent urination symptoms who was diagnosed with a urethral fibroepithelial polyp in the light of the literature.

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Objectives: To complement our previous findings regarding effect of ureteral access sheath (UAS) use, we checked RIRSearch database for patients who operated without using UAS. The aim of the study was to understand these new data better by comparing outcomes of retrograde intrarenal surgery (RIRS) that continued sheathless after a failed UAS insertion vs those planned and completed sheathless. Materials and Methods: Data of 195 patients who underwent sheathless RIRS for kidney and/or ureteral stones between 2011 and 2021 were retrieved from the database. Patients divided into two groups: cases who were planned and completed sheathless (n = 110, Group 1) and those who proceeded without UAS after insertion failure (n = 85, Group 2). After propensity score matching (PSM), each group consisted of 76 patients. Results: After PSM, stone-free rate for Group 1 (90.8%) was significantly higher than stone-free rate of Group 2 (76.3%) in sheathless RIRS (p = 0.02). Also postoperative complication rate was significantly lower in Group 1 (10.5%) than in Group 2 (27.6%) (p = 0.007). In Group 2, median operating time was longer (60 minutes, interquartile range [IQR]: 40-80) and more unplanned auxilliary procedure (22.4%) was needed than Group 1 (45 minutes, IQR: 40-50 and 3.9%) (both p = 0.001). Stone burden (odds ratio [OR]: 1.002, p = 0.019) and stone density (OR: 1.002, p = 0.003) were associated with high risk of residual stones after RIRS. Higher hydronephrosis grades were associated with increased stone-free rates (OR: 0.588 for residual stone risk, p = 0.024). Cases who completed sheathless by dusting all available stones, as planned preoperatively, were more likely to have stone-free status after RIRS than those who proceeded sheathless after UAS insertion failure (OR: 2.645, p = 0.024). Conclusions: Operation course after UAS insertion failure may be more challenging. In cases who performed without using UAS, surgeons who proceed with procedure sheathless after UAS insertion failure may more frequently run into complications and may fail achieving stone-free status compared with sheathless-planned cases.

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Introduction: Several scoring systems and nomograms have been developed to predict the success of retrograde intrarenal surgery. But no meta-analysis for the performance of scoring systems has yet been performed. The aim of this study was to compare predictive ability of recent scoring systems for stone-free rate of retrograde intrarenal surgery. Material and methods: PubMed and Web of Science databases were searched systematically between April and May 2021. The scoring systems which were validated externally or studied at least by two different researcher groups were selected for further analysis. Of 59 records, 14 studies met the inclusion criteria (n = 4137). Area under curve (AUC) values of selected scoring systems were pooled in random or fixed effects. The I2 test was used to quantify heterogeneity. Results: Eight, 5, 8, 4 and 3 studies included in meta-analyses for the modified Seoul National University Renal Stone Complexity Score (S-ReSC), R.I.R.S., Resorlu-Unsal Score (RUS), S.T.O.N.E., and Ito's Nomogram, respectively. We found pooled AUC values 0.709 (95% CI 0.670-0.748), 0.704 (95% CI 0.668-0.739), 0.669 (95% CI 0.646 to 0.692), and 0.771 (95% CI 0.724 to 0.818), for first four of them, respectively. Heterogeneity was very high to pool AUC values for Ito's nomogram. Conclusions: Although S.T.O.N.E. score showed higer pooled AUC value, this systematic review and meta-analysis has not revealed superiority of any scoring system. High heterogeneity between studies and dependencies between scoring systems make it difficult to design a comparative statistical model to generalize the findings. Also, limitations aside, neither scoring system has demonstrated good predictive/discriminative performance.

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Objective: The aim of the study was to assess whether severely obese patients have an increased risk of complications during and after retrograde intrarenal surgery (RIRS). Materials and Methods: The data of 639 consecutive patients undergoing RIRS for the treatment of upper tract urinary stones were analyzed retrospectively. The patients were divided into two groups according to their body mass index numbers (Group 1, <35; Group 2, ≥35). The patients' demographics, stone characteristics, operative outcomes, and complication rates were compared between the groups. The primary objective was to examine whether the intraoperative and postoperative complication rates were higher in patients with a body mass index of ≥35 kg/m2. Results: After matching of confounding factors, Group 1 comprised 135 patients, and Group 2 comprised 47 patients. The baseline characteristics were similar between the groups. There were no significant differences between groups for intraoperative complication rates (11.8% and 12.8%, respectively; p = 0.97). There was statistically significant difference in favor of Group 2 for postoperative complication rates (12.6% and 29.7%; respectively, p < 0.01), overall complication rates (22.9% and 38.2%; respectively, p = 0.02), mean operation time (56.15 vs 66.45 minutes; respectively, p = 0.01), and length of stay (1.4 vs 2.1 days; p = 0.03). Stone-free rates (75.5% vs 85.1%; respectively, p = 0.17) did not differ between groups. Conclusions: RIRS is an efficient and feasible treatment option for upper urinary tract stones in severely obese patients. However, higher possibility of postoperative, especially infectious, complication rates should be considered in these patients.

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Background: The aim of the study was to evaluate the impact of stone density on operative complication rates in retrograde intrarenal surgery (RIRS). Materials and Methods: A total of 473 consecutive patients undergoing RIRS for the treatment of upper tract urinary stones were included. To adjust for baseline confounders, one-to-one propensity score matching was performed. After matching, the patients were divided into two groups according to stone density (low density [LD] group, ≤970 Hounsfield unit [HU]; high density [HD] group, >970 HU). The patients' demographics, stone-related features, stone-free rates, and intraoperative and postoperative complication rates were compared between the groups. The primary objective was to evaluate whether the intraoperative and postoperative complication rates were higher in patients whose stone density was greater than 970 HU. Results: After propensity score matching, 170 of 210 LD and 170 of 263 HD patients undergoing RIRS were included. The baseline characteristics did not differ significantly between the groups. There were no significant differences between LD and HD patients with respect to intraoperative (5.9% and 8.8%, respectively; P = .29), postoperative (10.6% and 15.3%, respectively; P = .14), and overall complication rates (15.2% and 21.1%, respectively; P = .16). Stone-free status was achieved in 143 patients (84.1%) in the LD group and 148 patients (87%) in the HD group; the difference was not statistically significant (P = .27). Conclusion: Our results show that RIRS is a safe and effective minimally invasive procedure for the treatment of upper urinary tract stones, even in HD stones.

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Purpose: Retrograde intrarenal surgery (RIRS) is a safe and effective treatment option for upper urinary tract stones smaller than 2 cm. Although several studies have documented perioperative and postoperative complications related to RIRS, there exists limited data regarding the readmission and rehospitalization of patients after RIRS. The aims of the study were to document the rates of readmission and rehospitalization after RIRS and to determine the predictive factors for readmission and rehospitalization. Materials and Methods: In this study, we retrospectively analyzed patients who underwent RIRS for the treatment of renal stone disease and were unexpectedly readmitted to the hospital within 30 days after discharge. The hospital admission systems were used to determine readmissions and rehospitalizations. Readmission and rehospitalization rates, causes, and treatment procedures were evaluated. Univariate and multivariate analyses of clinicodemographic properties were performed to evaluate possible predictive factors for readmission and rehospitalization after RIRS. Results: A total of 1036 patients were included in the study. Of these patients, 103 (9.9%) were readmitted to the hospital. Among these readmissions, 35 patients (33.9%) were rehospitalized and 14 (13.6%) underwent surgical intervention. The most common reasons for readmission were renal colic and fever. The presence of preoperative pyuria (odds ratio [OR] 1.86), stone volume (OR 1.54), postoperative complications (OR 3.66), and stone-free status (OR 0.46) were predictive factors for readmission, whereas hospitalization time (OR 1.32), postoperative complications (OR 9.70), and stone-free status (OR 0.06) were predictive factors for rehospitalization after RIRS. Conclusion: Nearly 10% of patients who underwent RIRS were readmitted to the hospital within the first month after discharge, and some were rehospitalized. Preoperative pyuria, high stone volume, presence of postoperative complications, and low stone-free status predicted this readmission and rehospitalization. Clinicians must recognize these predictive factors and inform their patients about this possibility.

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BACKGROUND: Lithium is widely used in the treatment of bipolar disorders and may lead to nephrogenic diabetes insipidus (NDI), following long-term treatment. Metformin is considered the preferred initial therapy for patients with type 2 diabetes mellitus (T2D). OBJECTIVES: To investigate the protective effect of metformin on the kidney damage caused by lithium administration. MATERIAL AND METHODS: Using an animal model of chronic lithium-induced NDI, rats were divided into 4 groups: sham, metformin, lithium, and lithium + metformin. The effects of these treatments were examined using serum electrolytes, blood and tissue total antioxidant status, total oxidant status, the oxidative stress index, urine and blood osmolality, and tissue aquaporin-2 (AQP2) levels. Additionally, histopathological changes, including congestion, hydropic swelling, tubular necrosis, tubular atrophy, and Bowman's capsule dilatation, were evaluated. The total histopathological score was obtained by summing the scores for each pathological finding. RESULTS: In the lithium group, biochemical variables indicating NDI, including sodium, chloride and blood osmolality, increased, and urine osmolality decreased, compared to the sham group. With metformin treatment, the blood osmolality decreased from 328.17 mOsm/kg to 306.33 mOsm/kg, and urine osmolality increased from 349.67 mOsm/kg to 754.50 mOsm/kg (p = 0.004 and p = 0.001, respectively). Tissue AQP2 levels decreased with lithium administration but stabilized with metformin treatment. Additionally, in comparison to the lithium group, the total histopathological score in the metformin group declined from 8.0 to 2.0 (p = 0.002). CONCLUSIONS: Metformin may help protect the kidneys from lithium-induced NDI through the AQP2 regulating effect and a reduction in oxidative stress.

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AIM: The guidelines propose optical dilatation before retrograde intrarenal surgery (RIRS), but there are currently no evidence-based studies concerning the impact of optical dilatation with semirigid ureteroscopy (sURS). The aim of this study was to evaluate the effect of optical dilatation through sURS prior to the RIRS procedure on the success and complications of RIRS. METHODS: A total of 422 patients were included in the retrospective multicentre study. The patients were divided into two groups according to whether sURS was to be performed. Patients' demographics, stone parameters and operative outcomes were compared. Surgical success was defined as no or up to 3-mm residual stone fragments without the need for additional procedures. The independent predictors for surgical success were determined with a multivariable logistic regression model. RESULTS: Of the 422 patients, 133 (31.5%) were in the sURS group and 289 (68.5%) were in the non-sURS group. Stone characteristics and patients' demographics were similar between the groups. Operation time in the sURS group was significantly longer (compared with the non-sURS group, P < .0001). A ureteral access sheath (UAS) could not be placed in four (3.0%) patients in the sURS group, nor in 25 (8.7%) patients in the non-sURS group (P = .03). Compared with the non-sURS group, the intraoperative complication rate was lower in the sURS group (14 [4.8%] vs 1 [0.8%], P = .04). The surgical success rate was higher in the sURS group (P = .002). Nevertheless, sURS had no independent effect on surgical success. We found two independent predictors for surgical success rate: stone number (P < .0001, OR:2.28) and failed UAS placement (P = .035, OR:3.49). CONCLUSIONS: Optical dilatation with sURS before RIRS increases surgical success by raising the rate of UAS placement and reducing the rate of intraoperative complications. We suggest that this method can be routinely applied to patients who have not been passively dilated with a JJ stent.

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AIMS: To evaluate the effect of pre-RIRS ESWL on the efficiency and safety of RIRS in the treatment of proximal ureter stones. METHODS: The patients in the study population were divided into two groups. Group-1 was composed of patients who had undergone ESWL for proximal ureter stones before RIRS and Group-2 was composed of patients who directly underwent RIRS without any prior ESWL. The clinical and demographic properties of the patients were analysed in the RIRSearch database. The operative outcomes, peroperative complications, postoperative complications, hospitalisation time and stone-free rates were compared between the groups. RESULTS: There were 56 patients in Group 1 and 95 patients in Group 2. The demographic and clinical properties were similar between the groups. The stone-free rates, peroperative complications and postoperative complications were also similar between the groups; however, the fluoroscopy time was significantly higher in Group 1 (P = .043). The cut-off duration of 10 weeks between ESWL and RIRS had reasonable/favourable discriminating ability, with a 51% sensitivity and 88% specificity rate for stone-free status. CONCLUSION: Performing ESWL on the proximal ureter stones before RIRS did not change the efficacy and safety of RIRS. The time between the patient's last ESWL session and RIRS had a predictive value for stone-free status, but did not have any effect on complications.

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