Flexible ureterorenoscopy for lower pole stones: influence of the collecting system's anatomy

Clinical comparative study of single-use and reusable digital flexible ureteroscopy for the treatment of lower pole stones: a retrospective case-controlled study

OBJECTIVES

To compare the clinical efficacy and safety of single-use and reusable digital flexible ureteroscopy for the treatment of lower pole stones.

METHODS

We enrolled 135 patients underwent reusable flexible ureteroscopy (FURS) and 78 patients underwent single-use digital FURS. Demographic, clinical variables, anatomical parameters of the lower calyx and perioperative indicators were compared in the two groups.

RESULTS

Thirty-six patients in the infundibuloureter angle (IPA) < 45° subgroup had a mini-percutaneous nephrolithotomy (mini-PCNL), including 25 patients in the reusable FURS group and 11 patients in the single-use FURS group. The demographic and clinical variables in the two FURS groups were comparable. There was no statistical difference in the success rate of stone searching (P > 0.05). In terms of the success rate of lithotripsy, there was also no statistical difference in the IPA ≥ 45° subgroup (P > 0.05), whereas single-use FURS was superior in the IPA < 45° subgroup (χ2 = 6.513, P = 0.011). The length of the working fiber in the reusable FURS and single-use FURS groups was 3.20 ± 0.68 mm and 1.75 ± 0.47 mm, respectively (t = 18.297, P < 0.05). The use of a stone basket in the reusable FURS (31/135, 23.0%) was significantly higher than that in the single-use FURS (8/78, 10.3%) (χ2 = 5.336, P = 0.021). Compared with the reusable FURS group, the single-use FURS group had shorter operation times (P < 0.05) and higher stone-free rate (SFR) (χ2 = 4.230, P = 0.040). There was no statistical difference in the intraoperative transfer of mini-PCNL and postoperative complications between the two groups (P > 0.05).

CONCLUSIONS

Single-use and reusable FURS are alternative methods for removal of lower pole stones (i.e., 2 cm or less). Single-use FURS has a high success rate of lithotripsy, shorter operation time, and high stone-free rate.

Effect of infundibulopelvic angle on outcomes of ureteroscopy: a systematic review and meta-analysis

PURPOSE

The infundibulo-pelvic angle (IPA) is reportedly a predictor of successful ureteroscopy for lower pole renal stones, however there is uncertainty at which IPA success is likely. We therefore aimed to perform a meta-analysis and determine at which the angle of likely success and failure.

METHODS

We performed a systematic review and meta-analysis as per Cochrane guidelines in accordance to the PRISMA statement. The review was registered with PROSPERO prior to commencement (ID: CRD42022296732). We included studies reporting on outcomes of ureteroscopy for lower pole stones, with IPA. We excluded patients undergoing alternative treatments for lower pole stones, anatomical abnormalities and studies with < 10 patients. We assessed bias with the Newcastle-Ottawa scale. We performed meta-analysis in R, and summarised the findings as per GRADE.

RESULTS

Overall, there were 13 studies included, with 10 included for meta-analysis. These studies covered n = 1964 patients (71% stone free). Overall, the stone free patients had a significantly less acute mean IPA (52o ± 9o), compared to the non-stone free patients (39o ± 7o), on meta-analysis (REM MD = -13.0, 95% CI: -18.7 to -7.2, p < 0.001). On examination of forest plots, at IPA < 30o no patients were stone free, whilst > 50o all were stone free. Risk of bias was moderate, and certainty of evidence was 'very low'.

CONCLUSION

With a very low certainty of evidence, we demonstrate that at an IPA of < 30o no patient is stone free, whilst > 50o all patients (in this review) are stone free. More evidence is therefore needed.

Assessment of Factors Responsible for Stone-Free Status After Retrograde Intrarenal Surgery

Aim The study aimed to evaluate the predictive factors that determined stone-free rate (SFR) after retrograde intrarenal surgery (RIRS). Materials and methods This prospective study was conducted on 183 patients undergoing RIRS for renal stones. Patients were categorized into two groups, depending on stone-free status one month following the procedure. SFR was defined as the complete absence of stones or stones <4 mm. The parameters studied included patient demographics, presence of hydronephrosis, presence of preoperative double J-stent, abnormal renal anatomy, and stone characteristics (stone burden, stone number, stone density, stone location, lower pole infundibulopelvic angle, and lower pole renal infundibular length (RIL)). Univariate and multivariate analyses were performed to identify risk factors for residual stones. We assessed the predictive ability of the RIRS score and Resorlu-Unsal stone score (RUSS) for evaluating SFR utilizing receiver operating characteristic (ROC) analysis. Results 183 patients were included in the study with a median age of 51 years. 131 (71.6%) patients were declared stone-free after the procedure. The mean stone size and density were 16.9 SD±7.5 mm and 1038 SD±342 Hounsfield units (HU) respectively. Stone-free patients had lower stone size (14.3 mm vs. 23.6 mm, p<0.01) and stone density (970 HU vs. 1211 HU, p<0.01) compared to non-stone-free patients. Patients with residual stones had steeper lower pole renal infundibulopelvic angle (RIPA) (31.3° vs. 40.7°, p<0.01) and longer RIL (26.6 mm vs. 21.1 mm, p<0.01). Stone multiplicity (p<0.01), lower pole stone location (p<0.01), and renal malformations (p<0.01) were significant influencing factors for residual renal stones after RIRS. Multivariate analysis revealed stone size, stone density (HU), and stone location as independent predictors for SFR after RIRS. Among the scoring systems, the RIRS score had the highest diagnostic accuracy for SFR (area under the curve (AUC): -0.882, 95% CI-0.828-0.936). Conclusion Stone size, stone density (HU), and stone number are important predictors of SFR after RIRS. Lower pole stone location and abnormal renal anatomy play a substantial role in determining SFR after RIRS. In lower pole stones, a long RIL and acute RIPA negatively influence SFR. Additionally, the RIRS score was found to be a better predictor for SFR than the RUSS score.

Optimizing outcome reporting after robotic flexible ureteroscopy for management of renal calculi: Introducing the concept of tetrafecta

Robotic flexible ureteroscopy (RFURS) has shown encouraging results in terms of stone free rate (SFR) and better ergonomics compared to conventional FURS. However, few studies have reported its outcomes. The goal of this study was to report our initial results of RFURS, furthermore we proposed a novel metrics for composite outcome reporting named tetrafecta. A retrospective analysis of electronic records of 100 patients treated with RFURS for renal stones between 2019 till 2023 was performed. Tetrafecta criteria included, complete stone removal after a single treatment session, without auxiliary procedures, absence of high-grade complications (GIII-V) and same-day hospital discharge. Mean patient age and stone size were 40.7 ± 9.2 and 11.7 ± 5.8 mm, respectively. Median stone volume was 916 (421-12,235) mm3. Twenty-eight patients had multiple renal stones. Staghorn stones were seen in 12 patients. Preoperative DJ stent was fixed in 58 patients. Median operative time and stone treatment time were 116 min (97-148) and 37 (22-69) min. The median stone treatment efficiency (STE) was 21.6 (8.9-41.6). A strong positive correlation between stone volume and STE (R = 0.8, p < 0.0001). Overall, 73 patients were stone free after the initial treatment session while tetrafecta was achieved in 70 patients. Univariate analysis showed that the stone size (p = 0.008), acute infundibulopelvic angle (p = 0.023) and preoperative stenting (p = 0.017) had significant influence on achieving tetrafecta. Multivariate analysis identified preoperative stenting (OR 0.3, 95% CI 0.1-0.8, p = 0.019) as the only independent predictor of tetrafecta achievement. A comprehensive reporting methodology for reporting outcomes of RFURS is indicated for patient counseling and comparing different techniques. Tetrafecta was achieved in 70% of cases. Presence of significant residual stones ≥ 3mm was the leading cause of missing tetrafecta. Absence of preoperative stent was the only predictor of missing tetrafecta.

The Saudi urological association guidelines on urolithiasis

Aims

The Saudi Urolithiasis Guidelines are a set of recommendations for diagnosing, evaluating, and treating urolithiasis in the Saudi population. These guidelines are based on the latest evidence and expert consensus to improve patient outcomes and optimize care delivery. They cover the various aspects of urolithiasis, including risk factors, diagnosis, medical and surgical treatments, and prevention strategies. By following these guidelines, health-care professionals can improve care quality for individuals with urolithiasis in Saudi Arabia.

Panel

The Saudi Urolithiasis Guidelines Panel consists of urologists specialized in endourology with expertise in urolithiasis and consultation with a guideline methodologist. All panelists involved in this document have submitted statements disclosing any potential conflicts of interest.

Methods

The Saudi Guidelines on Urolithiasis were developed by relying primarily on established international guidelines to adopt or adapt the most appropriate guidance for the Saudi context. When necessary, the panel modified the phrasing of recommendations from different sources to ensure consistency within the document. To address areas less well covered in existing guidelines, the panel conducted a directed literature search for high quality evidence published in English, including meta analyses, randomized controlled trials, and prospective nonrandomized comparative studies. The panel also searched for locally relevant studies containing information unique to the Saudi Arabian population. The recommendations are formulated with a direction and strength of recommendation based on GRADE terminology and interpretation while relying on existing summaries of evidence from the existing guidelines.

Does displacement of lower pole stones during retrograde intrarenal surgery improves stone-free status? A systematic review and meta-analysis

PURPOSE

Kidney stones are one of the most common urological diseases worldwide. The size and location of the stone are the most important factors in determining the most suitable treatment options. The aim of this review was to evaluate the displacement of lower pole stones.

METHODS

Three studies assessing the efficacy of translocating kidney stones from the lower pole of the kidney to other locations during retrograde intrarenal surgery published in the last 20 years were included. A systematic search was conducted in the PubMed, Embase, Latin American and Caribbean Health Sciences Literature (LILACS), and Web of Science databases using the following search terms: "Lower pole," "Lithotripsy." Meta-analysis was performed using Review Manager version 5.4.

RESULTS

Stone-free rates were improved through displacement (odds ratio - OR = -0.15; 95% confidence interval-95%CI -0.24--0.05; p = 0.002; I2 = 21%), but at the cost of increased surgical duration (mean difference = -12.50; 95%CI -24.06--0.95; p = 0.03; I2 = 94%). Although this represents a potentially negative outcome, the improvement in clearance rates justifies the additional investment of time and effort.

CONCLUSIONS

Displacement of lower pole kidney stones for subsequent lithotripsy brings significant benefits in terms of stone-free rate, with no difference in laser energy usage. However, it results in increased surgical time. Despite these factors, the benefits to patients undergoing the procedure are substantial.

Flexible ureteroscopy for lower pole calculus: is it still a challenge?

PURPOSE

Flexible ureteroscopy (fURS) is steadily gaining popularity in the management of renal calculi, including those located in the lower pole (LP). Due to difficulty in accessing to the LP of kidney in minority of cases with fURS and reports of lower stone-free rate (SFR), it is still considered as a challenge in selected cases. The purpose of the review was to analyze the various aspects of fURS for LP stones.

METHODS

An extensive review of the recent literature was done including different factors such as anatomy, preoperative stenting, stone size, flexible scopes, types of lasers, laser fibers, suction, relocation, stone-free rates, and complications.

RESULTS

The significance of various lower pole anatomical measurements remain a subject of debate and requires standardization. Recent improvements in fURS such as single-use digital scopes with better vision and flexibility, high power laser, thulium fiber laser, smaller laser fiber, and accessories have significantly contributed to make flexible ureteroscopy  more effective and safer in the management of LP stone. The utilization of thulium fiber lasers in conjunction with various suction devices is being recognized and can significantly improve SFR.

CONCLUSIONS

With the significant advancement of various aspects of fURS, this treatment modality has shown remarkable efficacy and gaining widespread acceptance in management of LP kidney stones. These developments have made the fURS of LP stones less challenging.

Residual fragment size following retrograde intrarenal surgery: a critical evaluation of related variables

Given the limited data on the predictive factors of residual kidney stone size after flexible ureteroscopy (fURS), this study aims to investigate the variables affecting residual stone size. The medical records of 642 patients without complications being treated for kidney stones with fURS between July 2014 and May 2022 were reviewed retrospectively, and the information of the 170 patients in whom residual stones were found was recorded. In addition to patient-specific factors and stone characteristics, length of postoperative hospital stay, postoperative fever, and preoperative antiaggregant use were evaluated. Of the 170 patients ultimately included in the study. The mean age was 51.56 (± 14.70). The mean stone size was 14.01 mm (± 5.75), the mean residual stone size was 7.04 mm (± 2.51), and the mean stone density was 829 Hounsfield units (± 395.06). The mean infundibulopelvic angle (IPA) was 49.37º (± 15.37), and 41.2% of the stones were non-opaque. The mean parenchymal thickness was 22.88 mm (± 5.55). 34 patients were on antiaggregant therapy. Preoperative stone size increases in stone density and decreases in IPA were found to be correlated with increase residual stone size (p < 0.001, p < 0.001, and p < 0.001, respectively). In addition, larger residual stones were observed after the fURS procedure in patients using anticoagulants and those without hydronephrosis (p = 0.02 and p = 0.016, respectively). Use of reliable predictive factors to forecast residual stone size after fURS may help to inform those treated and enable urologists to design rational surgical strategies.

A single center comparative study of two single use digital flexible ureteroscopy in the management of renal stones less than 2 cm

PURPOSE

For renal stones < 2 cm, guidelines recommend the use of retrograde intrarenal surgery as a first line treatment option. Many available single use flexible ureteroscopy were found. We aim to compare the effectiveness of two single use flexible ureteroscopy; Pusen Uscope 3011 versus LithoVue in the management of renal stones less than 2 cm.

METHODS

Our study prospectively included 60 patients equally divided in to two groups: Pusen group and LithoVue group during the period from June 2020 to June 2021. The included patients were above 18 years old. Perioperative details as operative time, fluoroscopy time, hospital stay, and complications were recorded. Stone free rate was assessed. Base purchase cost was also compared.

RESULTS

There was no statistically significant difference between the two groups regarding age, gender, and body mass index (BMI), stones size, side, number and location. The perioperative evaluation and outcome had no statistically significant differences between the two groups regarding the operative time, hospital stay, access sheath use, and stone free rate or radiation exposure. Among all cases, we had 49 cases (81.6%) with no postoperative complications (21 cases for Pusen group and 28 cases for LithoVue group). The incidence of postoperative complications was significantly higher among Pusen group than LithoVue group (p = 0.02). Initial purchase cost for both FURS had no significant difference (P = 0.86).

CONCLUSION

RIRS can be performed effectively with Pusen 3011 and LithoVue single use flexible ureteroscopy in patients diagnosed with renal calculi < 2 cm with superior outcomes with LithoVue.

Unfavorable factors in accessing the pelvicalyceal system during retrograde flexible ureteroscopy (fURS)

Flexible ureteroscopy (fURS) is a well-established procedure for treating multiple upper-urinary tract pathologies, particularly renoureteral lithiasis. Endoscopes have undergone significant advancements, including miniaturization, improved optics, and increased maneuverability. In addition, advancements in accessory instruments, such as the performance of laser fibers, guidewires, and extraction probes, have played a significant role in improving the overall performance of flexible ureteroscopy procedures. However, despite these advancements, unique circumstances can make achieving optimum results during flexible ureteroscopy challenging. These include congenital renal anomalies (horseshoe kidneys, ectopic kidneys, rotation anomalies), as well as the unique intrarenal anatomy (infundibulopelvic angle, infundibular length) or the specifications of the endoscope in terms of maneuverability (active and passive deflection). This review explored challenging scenarios during flexible ureteroscopy procedures in the pyelocaliceal system.

Flexible ureteroscope capable of acute-angled and balanced omnidirectional bending based on soft and flexible porous tube and crossed control wiring

Flexible ureteroscopes (fURSs) have performance limitations in accessing acute-angled calyxes and omnidirectional bending. We propose and develop a fURS based on a soft and flexible porous tube and crossed control wiring to overcome these limitations. The fURS prototype comprises a flexible solid polyamide-12 tube and a stretch-retractable expanded polytetrafluoroethylene distal tube with 40% porosity connected by a unique cylindrical wire-routing hook (CWH). The series tube includes four crossed but not contacting loop-formed control wires to provide balanced omnidirectional bending and optimized distal tube bending performance. Bending performance was assessed compared with a conventional fURS, and feasibility studies were performed using a renal phantom. The prototype achieved a 275° omnidirectional maximum bend angle by combining up-down and right-left directions. The bent shape was more compact than the conventional fURS. Thus, the prototype achieved approximately a 1.6-fold larger maximal active bending angle within the restricted environment and a 5.5-fold larger passive bending angle. The crossed control wiring design reduced CWH offset distance by about 75% compared with conventional straight wire routing. The prototype exhibited considerably improved steering performance, exemplified by its ability to access an acutely angled calyx. Our design could improve treatment outcomes and shorten operation times associated with calyceal stone removal.

The study of double-J stent free mode of flexible ureteroscopy and laser lithotripsy: a single centre experience

OBJECTIVE

To evaluate the effectiveness and safety of flexible ureteroscopy in the treatment of kidney and upper ureteral calculi under double-J stent free mode.

METHODS

Data from patients who underwent flexible ureteroscopy and laser lithotripsy between February 2018 and September 2021 were retrospectively and analysed. Cases were grouped according to pre- or postoperative use of the double-J stent (6 Fr): Post-F group (preoperative double-J stent but no postoperative double-J stent); Pre-F group (no preoperative stenting but with postoperative double-J stent); and Routine group (preoperative and postoperative double-J stenting).

RESULTS

A total of 554 patients (390 male and 164 female) were included. The mean operation time was similar between the three groups, with no statistically significant difference. Incidence of grade 0-1 ureteral injury was significantly higher in the Pre-F group versus other groups, but there were no significant between-group differences in other operation-related complications. During follow-up, stent-associated complications were observed in the Pre-F and Routine groups, but not in the Post-F group. Stone clearance rates were similar between all groups at 1, 3 and 6 months following surgery.

CONCLUSIONS

Flexible ureteroscopy using double-J stent free mode was found to be safe, feasible and effective in treating renal and upper ureteral calculi.

Pelvicalyceal anatomy on the accessibility of reusable flexible ureteroscopy to lower pole calyx during retrograde intrarenal surgery

OBJECTIVE

This study aimed to evaluate the pelvicalyceal anatomy on accessibility of reusable flexible ureteroscopy (fURS) to the lower pole calyx during retrograde intrarenal surgery (RIRS).

METHODS

Here, 854 patients with ureteral or kidney stones with access to a renal collecting system using reusable fURS were classified into either the accessible group, in whom the deepest lower pole calyces could be touched; and the inaccessible group, in whom the deepest lower calyces could not be touched. We measured the infundibulopelvic angle (IPA), infundibular width (IW), infundibular length (IL), and calyceal pelvic height (CPH) using retrograde pyelograms and performed intergroup comparisons.

RESULTS

The median IPA, IW, IL, and CPH in the accessible and inaccessible group were 60.5° and 45.6° (p < 0.001), 10.8 and 9.4 mm (p < 0.001), 33.2 and 36.4 mm (p < 0.001), and 25.9 and 30.9 mm (p < 0.001), respectively. IPA (OR 0.963, 95% CI 0.952-0.974, p < 0.001) and IW (OR 0.519, 95% CI 0.331-0.816, p = 0.004) were significant risk factors of renal pelvicalyceal anatomy related to the accessibility of the lower pole calyces. The cut-off value for IPA and IW was 45.8°(p < 0.001) and 7.8 mm (p < 0.001), respectively.

CONCLUSIONS

IPA < 45.8° and IW <7.8 mm were negative predictors to access the lower pole calyces when using reusable fURS during RIRS.

Does Relocation of Lower Pole Stone During Retrograde Intrarenal Surgery Improve Stone-Free Rate? A Prospective Randomized Study

Purpose: The aim of this study was to compare the stone-free rate (SFR) of in situ treatment vs relocation and lithotripsy for lower pole stones of less than 2 cm following retrograde intrarenal surgery (RIRS). Methods: This prospective randomized study was undertaken from June 2019 to May 2020 in patients undergoing RIRS for lower pole renal stones less than 2 cm in diameter. Patients were randomized into two groups: in situ lithotripsy group and relocation lithotripsy group. The in situ lithotripsy group underwent laser lithotripsy for lower pole stones without relocation of the calculus, and the relocation lithotripsy group had their stones relocated to a favorable location using a tipless Nitinol basket, followed by laser lithotripsy. Laser lithotripsy was achieved using the holmium:YAG (Ho:YAG) laser (120 W) with a 200-μm laser fiber. A Double-J stent was placed in all patients at the end of the procedure. Patient demographics, stone characteristics, operative outcomes, and complications were evaluated. The SFR was determined at 1 month postoperatively with a kidney, ureter, and bladder radiograph (KUB) and ultrasound KUB. Results: Sixty-eight patients were included in the study: in situ group (n = 35) and relocation group (n = 33). The mean stone size and stone density were similar between the groups. The total operative duration, lasing duration, and total energy used were similar between the groups. At the 1-month follow-up, the complete SFR was 85.7% and 91% in the in situ lithotripsy and relocation lithotripsy groups, respectively (p = 0.506). Conclusions: Relocation followed by subsequent laser lithotripsy was associated with similar SFRs as with in situ laser lithotripsy for lower pole renal calculi less than 2 cm in diameter following RIRS using the Ho:YAG laser.

Single-Session Impact of High-Power Laser with Moses Technology for Lower Pole Stones in Retrograde Intrarenal Surgery: Retrospective Study

Background: This study aimed to evaluate the efficacy of a high-power holmium laser with Moses technology (MT) for the treatment of lower pole stones during retrograde intrarenal surgery (RIRS). Methods: Herein, 305 patients with lower pole stones who underwent RIRS using a high-power holmium laser with MT were retrospectively classified into the stone-free (SF) and non-SF groups. We measured the stone burden, stone volume, stone hardness, pre- or post-operative stent placement, infundibulopelvic angle (IPA), infundibular width (IW), infundibular length (IL), and calyceal pelvic height in terms of pelvicalyceal anatomy using retrograde pyelograms and evaluated the predictive factors of postoperative SF. Results: A total of 173 (56.7%) and 229 (75.1%) patients achieved a SF status on postoperative day one and at one month, respectively. Operation time in the SF group was shorter than that in the non-SF group (51.0 vs. 74.5 min). There were no significant differences in postoperative complications between the SF and non-SF groups. Significantly predictive risk factors in postoperative SF included total stone volume (odds ratio (OR), 1.056; 95% CI, 1.015-1.099; p = 0.007), IPA (OR, 0.970; 95% CI, 0.956-0.993; p = 0.009), and IW (OR, 0.295; 95% CI, 0.121-0.718; p = 0.007). The cut-off values of stone volume, IPA, and IW were 515.2 mm³, 46.8°, and 7.75 mm, respectively. Conclusions: A high-power holmium laser with MT in lower pole stones is a valuable option for positive outcomes and patient's safety. Larger stone volume, acute IPA, and narrow IW were negative predictors related to postoperative SF status.

Development of a novel predictive model for a successful stone removal after flexible ureteroscopic lithotripsy based on ipsilateral renal function: a single-centre, retrospective cohort study in China

OBJECTIVES

The aims of this study were to investigate the effect of preoperative ipsilateral renal function on the success of kidney stone removal with flexible ureteroscopic lithotripsy and to develop a predictive model based on the results.

DESIGN

Retrospective cohort study.

SETTING

Data from the 2001-2012 period were collected from the electronic records of West China Hospital, Sichuan University.

PARTICIPANTS

576 patients who underwent flexible ureteroscopic lithotripsy were included in the study.

PRIMARY OUTCOME

Stone-free rate (SFR) after the procedures.

RESULTS

In patients with suspected impaired kidney function, the overall SFR was 70.1%. Stone volume (OR 1.46; 95% CI 1.18 to 1.80), lower calyx stones (OR 1.80; 95% CI 1.22 to 2.65), age (OR 1.02; 95% CI 1.00 to 1.04), body mass index (OR 1.10; 95% CI 1.04 to 1.17) and estimated glomerular filtration rate of the affected kidney (OR 0.95; 95% CI 0.94 to 0.97) were identified as independent predictors of SFR. Lasso regression selected the same five predictors as those identified by univariate and multivariate logistic regression analyses, thus verifying our model. The mean area under the curve, based on 1000 iterations and 10-fold validation, was 0.715 (95% CI 0.714 to 0.716). The Hodges-Lehmann test and calibration curve analysis revealed no significant mismatch between the prediction model and the retrospective cohort.

CONCLUSION

Ipsilateral renal function may be a novel independent risk factor for kidney stone removal with flexible ureteroscopic lithotripsy. A novel nomogram for predicting SFR that uses stone volume, lower calyx stones, age, body mass index and estimated glomerular filtration rate was developed, but remains to be externally validated.

Retrograde intrarenal surgery in lateral position for lower pole stone: an initial experience from Single Academic Hospital

Retrograde intrarenal surgery (RIRS) was generally challenging in management of lower pole stone (LPS) since the unfavorable anatomy. Theoretically, LPS was prone to fall out and down to renal pelvis when patients turned to lateral position, thus to facilitate lithotripsy. The aim of the present study was to report our initial experience of RIRS in lateral position for LPS. From January 2020 to February 2021, 21 patients with LPS received RIRS in lateral position. The intraoperative finding, operation time, complications and stone-free rate (SFR) were recorded and analyzed. The mean stone size was 16.7 ± 2.4 mm, multiple stones in lower pole were noted in 38.1% (8/21) cases. The mean infundibular-pelvic angle (IPA) was 35.2 ± 6.9°, IPA less than 30° was noted in six cases (28.6%, 6/21). Mean operation time was 43.5 ± 6.3 min. Obvious stone fragments dropping from the lower calyx to renal pelvis during the lithotripsy were noted in 17 cases (81.0%). Only one case (4.8%) suffered postoperative fever (Clavien I), no severe complication (> Clavien II) was noted. Hospital stay was 1.1 ± 0.3 days, the SFR in postoperative 1 month was 85.7%. LPS was prone to fall out and down to renal pelvis when patients in lateral position, thus to facilitate the lithotripsy. RIRS in lateral position was feasible for the management of LPS; however, RCT with large sample was required to certify our initial finding.

Comparison of two techniques for the management of 2-3 cm lower pole renal calculi in obese patients

OBJECTIVE

To compare the outcomes of mini percutaneous nephrolithotomy (mPNL) and retrograde intrarenal surgery (RIRS) for the management of 2-3 cm lower pole renal calculi (LPC) in obese patients.

PATIENTS AND METHODS

120 obese patients with 2-3 cm LPC were randomly divided into mPNL group and RIRS group. Demography, clinical characteristics, perioperative complications, and stone free rate (SFR) were recorded. Stone-free status means no stone on computed tomography 3 months after surgery, or residual fragments were less than 3 mm.

RESULTS

Baseline characteristics were similar between the two groups. The mean stone burden was 585.39 ± 131.06 mm² in the mPNL group and 548.64 ± 123.55 mm² in the RIRS group (P = 0.125). The SFR of mPNL group was significantly better than that of RIRS group (86.2% vs 61.4%, P = 0.002). Besides, the overall complication rate was 22.4% in the mPNL group and 7% in the RIRS group (P = 0.02). Patients performed with mPNL required longer length of hospital stay than those with RIRS (P = 0.001). There were no significant differences in operative time and stone composition between the two groups.

CONCLUSION

In our study, both mPNL and RIRS are safe and effective techniques for the treatment of 2-3 cm LPC in obese patients. Compared to RIRS, mPNL has better SFR at the expense of the higher incidence of complications and prolonged length of hospital stay.

Comparison of the Efficacy and Safety of Extracorporeal Shock Wave Lithotripsy and Flexible Ureteroscopy for Treatment of Urolithiasis in Horseshoe Kidney Patients: A Systematic Review and Meta-Analysis

Background: Urolithiasis is the most common complication of horseshoe kidney (HK), which can be treated by extracorporeal shock wave lithotripsy (ESWL), flexible ureteroscopy (FURS), and percutaneous nephrolithotomy (PCNL). When comparing treatments of ESWL and FURS, it is unclear which is more efficient and safe. The objective of this study was to compare the efficacy and safety of FURS and SWL for the treatment of urolithiasis in HK patients. Methods: A systematic search of the Web of Science, PubMed, and EMBASE was performed in February 2021. Newcastle-Ottawa Scale (NOS) was used to assess the risk of bias in each study. Results: Five studies published between 2008 and 2018 were synthesized in the present meta-analysis. The study revealed that FURS compared with SWL had greater initial and overall stone-free rates (SFRs). Risk ratios (RRs) were 2.46 (P < 0.00001) in initial SFRs, 1.36 (P = 0.02) in overall SFRs. No differences were found in the retreatment ratio, RRs were 0.49 (P = 0.43). In addition, no major complications were encountered, and all the complications were mild to moderate. Conclusion: The study demonstrated that FURS and SWL are effective and safe treatments for patients with HK with stones (<20 mm). Moreover, FURS has greater clearance rates and lower complication rates than SWL.

Efficiency of retrograde intrarenal surgery in lower pole stones: disposable flexible ureterorenoscope or reusable flexible ureterorenoscope?

PURPOSE

The primary aim of this study to comparison of reusable and disposable flexible ureterorenoscope (fURS) efficiency in lower pole renal stone disease management. In addition, the secondary goal of this study was to evaluate the factors affecting stone-free rates (SFR) in lower pole stones.

MATERIALS AND METHODS

A prospective case-control study utilizing data from 122 consecutive ureteroscopic cases. The patients were divided into two groups according to the ureterorenoscope employed in the surgical intervention as disposable fURS (Group1, n:52) and reusable fURS (Group 2, n:70). Demographic characteristics, stone size, infundibulopelvic angle (IPA), SFR, hospitalization time, intraoperative complication rate (CR), operative time, preoperative or postoperative JJ stenting, and postoperative CR were analyzed.

RESULTS

There was no statistical difference between the demographic and renal stone-related data between the groups. Likewise, no difference is observed in term of intraoperative and postoperative outcomes such as fluoroscopy time, CR, and hospitalization time between the groups. Although SFR was higher in the disposable fURS group, there was no difference statistically. However, the operative time was longer in reusable fURS Group (47.02 ± 9.91 min in Group 1, and it was 57.97 ± 14.28 in Group 2) (p: 0.001). The multivariate regression analysis result to evaluate the factors of effect to operative time; the use of disposable fURS was associated with a 10.95-min decrease in procedure duration (p < 0.001).

CONCLUSIONS

Disposable fURS and reusable fURS have similar clinical efficiency and complication rates in the treatment of lower calyceal stones with RIRS. Nevertheless, disposable fURS is a useful treatment option for increased stone volume due to the advantages such as shorter operative time.

Single-use digital flexible ureteroscopes as a safe and effective choice for the treatment of lower pole renal stones: secondary analysis of a randomized controlled trial

OBJECTIVE

To compare the efficacy and safety of a single-use digital flexible ureteroscope (FURS) and a reusable FURS for the treatment of lower pole stones (LPS) smaller than 20 mm.

PATIENTS AND METHODS

We analyzed the data of 49 patients with LPS from our previous multicenter, randomized, open-label clinical trial in four hospitals in China. All patients underwent FURS for LPS with a single-use FURS ZebraScope™ (trial group) or a reusable FURS URF-V (control group). The efficacy endpoints assessed were the 1-month postsurgical stone-free rate (SFR), operative time, length of postoperative hospital stay, and mean reduction in hemoglobin level. The safety outcomes assessed were the presence of adverse events (AEs), severe AEs (SAEs), and postoperative complications.

RESULTS

The demographic and preoperative parameters were comparable between the 2 groups. The 1-month SFR was 84.00% for the ZebraScope™ group and 58.33% for the URF-V group (P<0.05). There was no difference between the two groups in the operative time (P=0.665), the length of hospital stay (P=0.308), the presence of postoperative complications (P=0.307), the presence of AEs (P=0.483), and the presence of SAEs (P = 0.141).

CONCLUSIONS

This study demonstrates that single-use digital FURS is a safe and effective option and can offer higher SFR than the reusable FURS in the treatment of LPS smaller than 20 mm. We recommend single-use digital FURS as an alternative to reusable FURS for the treatment of LPS.

Is Retrograde Intrarenal Surgery as Safe for Children as It Is for Adults?

INTRODUCTION

The primary aim of this study is to compare the efficacy and safety of retrograde intrarenal surgery (RIRS) among the children and adults with similar stone burdens and locations. Also, the secondary aim of this study is to identify the factors affecting the stone-free rates (SFRs) of RIRS.

METHODS

We retrospectively compared perioperative results, SFRs, and complication rates (CRs) between pediatric (group 1, n: 55) and adult (group 2, n: 220) age groups diagnosed with kidney stones and treated by flexible ureterorenoscopy using the same instruments. Furthermore, multivariate analysis was performed to determine the factors affecting the SFR.

RESULTS

A total of 275 patients (pediatric group: 55; adult group: 220) were included in this study. The mean age of pediatric and adult groups was 7.2 ± 5.3 and 43.9 ± 15.1, respectively. The mean stone size was 13.9 ± 6.6 mm in the pediatric group compared to 14.8 ± 6.7 mm in the adult group (p = 0.35). Stone localizations and number were similar. JJ stenting for passive dilatation and use of UAS were higher in the pediatric group (p = 0.002; p = 0.017). However, postoperative double pigtail stenting rate was higher in the adult group (p < 0.001). Total CR was 13.8% and mostly Clavien I-II, and no difference was observed between the 2 groups (p = 0.541). The SFRs between the groups were similar (pediatric group: 81.8%; adult group: 78.2%; p = 0.554). On multivariate analysis, stone size (p < 0.001) and lower calyx stone (p < 0.001) were the negative predictive factors for SFR.

CONCLUSION

There are small technical differences between pediatric patients and adult patients in our study, but RIRS in children is as safe and efficient as it is in adults.

Comparison of scoring systems for predicting stone-free status and complications after retrograde ıntrarenal surgery

PURPOSE

To compare the effectiveness of scoring systems in predicting stone-free rates (SFR) and complications following retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

We retrospectively analyzed 280 patients who underwent RIRS for kidney stones between 2016 and 2019. The Resorlu-Unsal Stone score (RUSS), Modified Seoul National University Renal Stone Complexity (S-ReSC) score, and R.I.R.S. scoring system score were calculated for each patient who was enrolled in the study. Subsequently, stone scoring systems were compared as to their predictive capability for SFR using receiver-operating characteristic curves. Furthermore, multivariate analysis was done to determine whether the scoring systems associated with SFR and complications.

RESULTS

The median patient age was 44 (35--56). The median RUSS, S-ReSC, and R.I.R.S scores were 0 (0-1), 1(1-2), and 6 (5-7), respectively. The overall SFR was 76.7%. The R.I.R.S. scoring system was found to have a higher predictive value in predicting postoperative SFR than the other two scoring systems (p < 0.001, AUC = 0,816). RUSS, R.I.R.S. score, and stone size were found to be independent predictive factors for SFR (p = 0.049, p = 0.024, p = 0.033, respectively). Complications were observed in 3.2%(9/280) of patients. Stone scoring systems were not statistically associated with complications. Operation duration was the only independent risk factor for complications (p = 0.010).

CONCLUSIONS

The R.I.R.S. scoring system was found to have a higher predictive value than RUSS and S-ReSC to predict SFR following RIRS in our study. However, none of the stone scoring systems was directly proportional to complications of RIRS.

The impact of the pelvicalyceal anatomy characteristics on the prediction of flexible ureteroscopy outcomes

Background

The anatomical architecture is a prominent factor in the outcomes of flexible ureteroscopy (FURS).

Aims and Objectives

The aim to regard the success of procedures based on Pelvicalyceal body that called Sampaio classification system.

Materials and Methods

A total of 125 FURS procedures were reviewed between December 2012 and December 2016 in our department. Seven patients were excluded from the study due to the horseshoe kidney in two cases and recurrent cystine stone configuration in five patients. The patient's renal collecting system anatomy characteristics are regarded, and they are classified into four main groups based on the mid-renal-zone anatomy assessed according to Sampaio Classification.

Results

Total stone-free rate (SFR) during the postoperative 1^st-month evaluation was noncontrast computerized tomography 75 (63.6%). The evaluation of the SFR in all subgroup of cases based on Sampaio classification noticed easily, SFR was significantly lower in subgroup A2 (30.4%) (P = 0.00), significantly higher in subgroup B2 (P = 0.008). The comparative analysis of the operative duration defined that it was the shortest (75.3 ± 18.1 min) in Type B1 subgroup cases, and the longest (84.7 ± 25.7 min) in the Type A2 subgroup cases. Even though this duration was found to be relatively higher in Type A2 subgroup cases than the others, this difference was not statistically significant (P = 0.271). Fluoroscopy time was noted to be the shortest (11.9 ± 13.4 s) in B1 subgroup and the longest in A2 subgroup with a statistically significant different (median: 21.3 ± 30.4) (P = 0.04). While 6 (5.1%) cases had Clavien 2 and 3 (2.5%) cases, demonstrated Clavien 3a complications.

Conclusion

The calyceal structure of the kidney affects the SFR; therefore, a detailed classification of pelvicalyceal could improve the outcomes, decrease the rate of auxiliary procedures and prevent the complications.

Consultation on kidney stones, Copenhagen 2019: aspects of intracorporeal lithotripsy in flexible ureterorenoscopy

Purpose

To summarize current knowledge on intracorporeal laser lithotripsy in flexible ureterorenoscopy (fURS), regarding basics of laser lithotripsy, technical aspects, stone clearance, lithotripsy strategies, laser technologies, endoscopes, and safety.

Methods

A scoping review approach was applied to search literature in PubMed, EMBASE, and Web of Science. Consensus was reached through discussions at the Consultation on Kidney Stones held in September 2019 in Copenhagen, Denmark.

Results and conclusions

Lasers are widely used for lithotripsy during fURS. The Holmium laser is still the predominant technology, and specific settings for dusting and fragmenting have evolved, which has expanded the role of fURS in stone management. Pulse modulation can increase stone ablation efficacy, possibly by minimizing stone retropulsion. Thulium fibre laser was recently introduced, and this technology may improve laser lithotripsy efficiency. Small fibres give better irrigation, accessibility, and efficiency. To achieve optimal results, laser settings should be adjusted for the individual stone. There is no consensus whether the fragmentation and basketing strategy is preferable to the dusting strategy for increasing stone-free rate. On the contrary, different stone scenarios call for different lithotripsy approaches. Furthermore, for large stone burdens, all laser settings and lithotripsy strategies must be applied to achieve optimal results. Technology for removing dust from the kidney should be in focus in future research and development. Safety concerns about fURS laser lithotripsy include high intrarenal pressures and temperatures, and measures to reduce both those aspects must be taken to avoid complications. Technology to control these parameters should be targeted in further studies.

A Novel Clinical-Radiomics Model Pre-operatively Predicted the Stone-Free Rate of Flexible Ureteroscopy Strategy in Kidney Stone Patients

Purpose: The purpose of the study is to develop and validate a novel clinical-radiomics nomogram model for pre-operatively predicting the stone-free rate of flexible ureteroscopy (fURS) in kidney stone patients. Patients and Methods: Altogether, 2,129 fURS cases with kidney stones were retrospectively analyzed, and 264 patients with a solitary kidney stone were included in a further study. For lower calyx calculi, a radiomics model was generated in a primary cohort of 99 patients who underwent non-contrast-enhanced computed tomography (NCCT). Radiomics feature selection and signature building were conducted by using the least absolute shrinkage and selection operator (LASSO) method. Multivariate logistic regression analysis was employed to build a model incorporating radiomics and potential clinical factors. Model performance was evaluated by its discrimination, calibration, and clinical utility. The model was internally validated in 43 patients. Results: The overall success rate of fURS was 72%, while the stone-free rate (SFR) for lower calyx calculi and non-lower calyx calculi was 56.3 and 90.16%, respectively. On multivariate logistic regression analysis of the primary cohort, independent predictors for SFR were radiomics signature, stone volume, operator experience, and hydronephrosis level, which were all selected into the nomogram. The area under the curve (AUC) of clinical-radiomics model was 0.949 and 0.947 in the primary and validation cohorts, respectively. Moreover, the calibration curve showed a satisfactory predictive accuracy, and the decision curve analysis indicated that the nomogram has superior clinical application value. Conclusion: In this novel clinical-radiomics model, the radiomics scores, stone volume, hydronephrosis level, and operator experience were crucial for the flexible ureteroscopy strategy.

Evaluation and comparison of scoring systems for predicting stone-free status after flexible ureteroscopy for renal and ureteral stones

OBJECTIVE

To evaluate four predictive scores for stone-free rate (SFR) after flexible ureterorenoscopy (f-URS) with holmium-YAG laser fragmentation of renal and ureteral lithiasis.

METHODS

We carried out a retrospective analysis of 800 f-URS procedures performed in our institution between January 2009 and December 2016. For each procedure, a single surgeon calculated the following scores: S.T.O.N.E score; Resorlu Unsal Stone Score (RUSS); modified Seoul National University Renal Complexity (S-ReSC) score; and Ito's score.

RESULTS

Overall SFR was 74.1%. Univariate analysis demonstrated that stone size (p<0.0001), stone volume (p<0.0001), stone number (p = 0.004), narrow lower pole infundibulopelvic angle (IPA) (p = 0.003) and lower pole location + IPA <45° (p = 0.011) were significantly associated with SFR. All scores differed between the stone-free and non-stone-free groups. Area under the curve of the receiving operator characteristics curve was calculated for each score: 0.617 [95%CI: 0.575-0.660] for the S.T.O.N.E score; 0.644 [95%CI: 0.609-0.680] for the RUSS; 0.651 [95%CI: 0.606-0.697] for the S-ReSC score; and 0.735 [95%CI: 0.692-0.777] for Ito's nomogram.

CONCLUSION

All four scores were predictive of SFR after f-URS. Ito's score was the most sensitive. However, the performance of all scores in this analysis was lower than in developmental studies.

Does the renal parenchymal thickness affect the efficacy of the retrograde intrarenal surgery? A prospective cohort study

Retrograde intrarenal surgery (RIRS) is one of the minimally invasive main treatment modalities in renal stone disease. There are many factors which affect stone-free rate (SFR). Our study was based on the hypothesis that higher renal parenchymal thickness (RPT) which may include higher average number of nephrons provides better diuresis. We investigated the efficacy of RPT on success of RIRS. This study is a single-centered prospective surgical cohort study. A total of 383 patients were analyzed. Regularly followed 304 patients with unilateral kidney stone at single pole or renal pelvis and who underwent single-session RIRS were included in the final analysis, and the patients' preoperative and postoperative 1st and 3rd months' data were evaluated. RPT was measured on the non-contrast computed tomography (CT) images. ROC analysis was performed to estimate the cutoff value of RPT for SFR. Univariate and multivariate logistic regression analyses were used to model the relationship between RPT and SFR after RIRS. ROC analysis revealed the best cutoff value of the RPT for predicting residual stone as 19 mm for both the 1st and 3rd month visits with Youden indexes of 0.397 and 0.406, respectively. To the best of our knowledge, this is the first study which evaluated the effect of RPT on the efficacy of RIRS. RPT measurement is a cost-effective method that can be easily performed on routinely applied non-contrast CT and may have predictive value for the surgical success in patients with nephrolithiasis.

What is the exact definition of stone dust? An in vitro evaluation

PURPOSE

To propose a size-related definition of stone dust produced by lithotripsy of urinary stones.

METHODS

Stone dust was defined as particles small enough to adhere to the following criteria: (1) spontaneous floating under 40 cm H₂O irrigation pressure; (2) mean sedimentation time of > 2 s through 10 cm saline solution; (3) fully suitable for aspiration through a 3.6 F working channel. Irrigation, sedimentation, and aspiration tests were set up to evaluate each criterion. Primary outcome was particle size limit agreeing with all three criteria. Stone particles with a given size limit (≤ 2 mm, ≤ 1 mm, ≤ 500 µm, ≤ 250 µm, ≤ 125 µm and ≤ 63 µm) were obtained from laser lithotripsy, including samples from prevailing stone types: calcium oxalate monohydrate, calcium oxalate dihydrate, uric acid, carbapatite, struvite, brushite, and cystine.

RESULTS

All particles ≤ 250 µm from all stone types were in agreement with all three criteria defining stone dust, except for struvite where size limit for a positive irrigation and sedimentation test was ≤ 125 µm.

CONCLUSION

A size limit of ≤ 250 µm seems to generally adhere to our definition of stone dust, which is based on floating and sedimentation proprieties of stone particles, as well as on the ability to be fully aspirated through the working channel of a flexible ureteroscope.

Influence of Lower Pole Infundibulopelvic Angle on Success of Retrograde Flexible Ureteroscopy and Laser Lithotripsy for the Treatment of Renal Stones

Objectives: Influence of renal anatomy on success rates for shockwave lithotripsy has been reported in the literature with emphasis on lower pole anatomy. Influence of renal anatomy has not been evaluated in the setting of ureteroscopy and laser lithotripsy for stone treatment. This study analyzed the influence of infundibulopelvic angle (IPA) of the lower pole on the outcomes of ureteroscopy and laser lithotripsy with respect to stone-free rate and surgical recurrence. Materials and Methods: We retrospectively analyzed 735 renal units undergoing retrograde flexible ureteroscopy (fURS) with laser lithotripsy between January 2009 and December 2016. All cases were performed at a single institution. No exclusion criterion was applied with regard to preoperative stone location. Success was defined as no evidence of residual stone fragments on kidney, ureter, and bladder radiograph within 2 months of surgery. Failure was defined as any stone present on imaging. Lower pole IPA was measured on intraoperative retrograde pyelogram as described by Elbahanasy et al. Univariate and multivariate analyses of factors contributing to stone-free rate were performed. Secondary outcomes included surgical recurrence-free survival. Results: Of the 735 cases evaluated, 243 cases had a retrograde pyelogram stored in our Picture Archiving and Communication System (PACS) sufficient for IPA interpretation. Of these patients, 122 (50%) were women. In total, 127 patients (52.3%) were stone free on follow-up imaging, whereas 116 (47.7%) had residual stone burden. In total, 144 (59%) patients had ≤3 mm stone burden on follow-up imaging. In multivariate analysis, residual stone fragments were significantly associated with acute IPA <90° (<0.001), lower pole stones preoperatively (<0.001), and larger stone size (0.001). IPA <90° and larger stone size were both found to be statistically significantly associated with need for repeat surgery. Conclusions: Our data show that more acute IPA and larger preoperative stone size negatively affect stone-free rate and need for repeat surgery after retrograde fURS with laser lithotripsy for treatment of renal stones.

Evaluation of flexible ureteroscope with an omni-directional bending tip, using a JOYSTICK unit (URF-Y0016): an ex-vivo study

PURPOSE

To compare the range of reach of our newly designed omni-directional ureteroscope (URF-Y0016), compared to the commonly used URF-P6, FlexX2s, and LithoVue™ scopes, in the upper, middle, and lower calyces in an ex-vivo pyelocaliceal model.

METHODS

We fabricated a three-dimensional pyelocaliceal model of the upper, middle, and lower pole calyces using urethane and acrylic resin. The inner surface of the dome of each calyx was engraved with reference lines along eight directions, set at 10° of latitude from the top to the base of the dome, and at angles of 0-90°, to precisely determine the range of reach of each scope. The main feature of the URF-Y0016 scope is the omni-directional bending of the tip of the flexible ureteroscope, with the control of these four directions integrated into a handgun-type control unit with a joystick. The range of reach within each calyx was measured by four expert surgeons.

RESULTS

The URF-Y0016 scope provided a greater range of reach along all directions in the lower pole calyx compared to URF-P6, FlexX2s, and LithoVue™ scopes (p < 0.001), particularly along the anterior-posterior direction in the lower lobe calyx. However, the URF-Y0016 scope did not influence the improvement of reach range in the upper and middle pole calyx compared to URF-P6, FlexX2s, and LithoVue™ scopes (p = 0.08, p = 0.296).

CONCLUSION

The novel design of the URF-Y0016 could improve treatment outcomes for calyceal stones in the lower pole in practice.

Laser fibre, rather than the stone, may harm the scope: retrospective monocentric analysis of 26 pre- and intraoperative factors of flexible ureteroscope (fURS) damage

PURPOSE

The increasing number of flexible ureteroscopy procedures, the fragility of devices and their repair costs are a burden for urological departments worldwide. The objective was to investigate the impact of 26 pre- and intraoperative factors on reusable flexible ureteroscope (fURS) damage.

METHODS

All procedures were conducted with reusable fURS: Karl Storz Flex-X2 or Olympus URF-V. Statistical analysis was performed in RStudio (1.0.136) with Chi-square test and Mann-Whitney U tests (MWU).

RESULTS

In total, 416 flexible ureteroscopies, performed between September 2013 and June 2017, were analysed. 283 (68.03%) of these were for kidney stone surgery, and 133 (31.97%) for diagnostic purposes. In total, 39 (9.38%) devices were postoperatively deemed defective. The application of reusable laser fibre through fURS was more common in cases with documented defects [17/39 (43.59%) vs. 102/377 (27.06%), p = 0.047]. Other factors such as application of nitinol basket, biopsy via fURS, insertion of access sheath (UAS), as well as stone burden [median kidney stone maximal diameter: 6 mm (min 2.0; max 30.0) vs. 6 mm (min 1.0 vs. max 30.0)] showed no influence on fURS damage rate (p > 0.05). The infundibulopelvic angle (IPA) was steeper in cases with fURS damage as compared to cases without damage [median 44.0° (min 20.0; max 81.0) vs. 55.0 (min 7.0; max 122.0), p < 0.001].

CONCLUSIONS

Application of laser fibre via fURS can be considered as a risk factor of fURS damage. Stone burden, as well as the usage of not-sharp ended devices as nitinol baskets or forceps, is primarily not responsible for fURS damage.

A comprehensive literature-based equation to compare cost-effectiveness of a flexible ureteroscopy program with single-use versus reusable devices

PURPOSE

To critically review all literature concerning the cost-effectiveness of flexible ureteroscopy comparing single-use with reusable scopes.

MATERIALS AND METHODS

A systematic online literature review was performed in PubMed, Embase and Google Scholar databases. All factors potentially affecting surgical costs or clinical outcomes were considered. Prospective assessments, case control and case series studies were included.

RESULTS

741 studies were found. Of those, 18 were duplicated and 77 were not related to urology procedures. Of the remaining 646 studies, 59 were considered of relevance and selected for further analysis. Stone free and complication rates were similar between single-use and reusable scopes. Operative time was in average 20% shorter with digital scopes, single-use or not. Reusable digital scopes seem to last longer than optic ones, though scope longevity is very variable worldwide. New scopes usually last four times more than refurbished ones and single-use ureterorenoscopes have good resilience throughout long cases. Longer scope longevity is achieved with Cidex and if a dedicated nurse takes care of the sterilization process. The main surgical factors that negatively impact device longevity are lower pole pathologies, large stone burden and non-use of a ureteral access sheath. We have built a comprehensive fi nancial costeffective decision model to fl exible ureteroscope acquisition.

CONCLUSIONS

The cost-effectiveness of a fl exible ureteroscopy program is dependent of several aspects. We have developed a equation to allow a literature-based and adaptable decision model to every interested stakeholder. Disposable devices are already a reality and will progressively become the standard as manufacturing price falls.

Endoscopic treatment of lower pole stones: is a disposable ureteroscope preferable? Results of a prospective case-control study

Introduction

The best option for lower pole stone management is still under debate. With the recent incorporation of disposable ureteroscopes, discussion on this topic has been renewed. The aim of the present study was to compare the results obtained with flexible disposable ureteroscopes with those obtained using reusable ureteroscopes in the treatment of inferior calyx stones.

Material and methods

A case-control study was carried out using data registered prospectively in a database at our center. The clinical results obtained in two groups of patients were analyzed. In the first group of patients, a reusable flexible fiber-optic ureteroscope (Cobra^®, Richard Wolf) was used, and in the second group, a disposable flexible ureteroscope was used (Uscope 3022^®, Pusen Medical). The variables analyzed included: operative time, fluoroscopy time, need for postprocedure ureteral catheter, stone-free rate (fragments <1 millimeter) and complications. The results were evaluated using a Student's t test, a Mann-Whitney test and a Fisher's test.

Results

There were 31 cases with disposable ureteroscopes and 30 cases with a reusable ureteroscope. Both groups were comparable in their demographic and clinical variables. The characteristics regarding length, width and angle of the infundibulum (measured by retrograde ureteropyelography) were also comparable. There were no differences in the clinical findings with respect to the stone-free rate, need for a ureteral catheter, complications or hospital stay. Significant differences were found in the average surgery time (56.1 vs. 77 minutes; P = 0.01) and in the fluoroscopy time (66.1 vs. 83.4 seconds; P = 0.02), both favoring the use of single use ureteroscopes.

Conclusions

In this study, disposable flexible ureteroscopes have been validated as an option that is in the least equivalent to reusable ureteroscopes based on clinical results. The shorter surgical and fluoroscopy durations are possible advantages considering the high costs associated with time spent in the operating room and the need to reduce ionizing radiation.

[Application of machine learning models in predicting early stone-free rate after flexible ureteroscopic lithotripsy for renal stones]

OBJECTIVE

To establish predictive models based on random forest and XGBoost machine learning algorithm and to investigate their value in predicting early stone-free rate (SFR) after flexible ureteroscopic lithotripsy (fURL) in patients with renal stones.

METHODS

The clinical data of 201 patients with renal stones who underwent fURL were retrospectively investigated. According to the stone-free standard, the patients were divided into stone-free group (SF group) and stone-residual group (SR group). We compared a number of factors including patient age, body mass index (BMI), stone number, stone volume, stone density and hydronephrosis between the two groups. For low calyceal calculi, renal anatomic parameters including infundibular angle (IPA), infundibular width (IW), infundibular length (IL) and pelvic calyceal height (PCH), would be measured. We brought above potential predictive factors into random forest and XGBoost machine learning algorithm respectively to develop two predictive models. The receiver operating characteristic curve (ROC curve) was established in order to test the predictive ability of the model. Clinical data of 71 patients were collected prospectively to validate the predictive models externally.

RESULTS

In this study, 201 fURL operations were successfully completed. The one-phase early SFR was 61.2%. We built two predictive models based on random forest and XGBoost machine learning algorithm. The predictive variables' importance scores were obtained. The area under the ROC curve (AUROC) of the two predictive models for early stone clearance status prediction was 0.77. In the study, 71 test samples were used for external validation. The results showed that the total predictive accuracy, predictive specificity and predictive sensitivity of the random forest and XGBoost models were 75.7%, 82.6%, 60.0%, and 81.4%, 87.0%, 68.0%, respectively. The first four predictive variables in importance were stone volume, mean stone density, maximal stone density and BMI in both random forest and XGBoost predictive models.

CONCLUSION

The predictive models based on random forest and XGBoost machine learning algorithm can predict postoperative early stone status after fURL for renal stones accurately, which will facilitate preoperative evaluation and clinical decision-making. Stone volume, mean stone density, maximal stone density and BMI may be the important predictive factors affecting early SFR after fURL for renal stones.

Role of pelvicalyceal anatomy in the outcomes of retrograde intrarenal surgery (RIRS) for lower pole stones: outcomes with a systematic review of literature

Controversies exist on the influence of lower pole anatomy (infundibular pelvic angle, IPA; infundibular length, IL; and infundibular width, IW) for success and outcomes related to the treatment of stones in the lower pole. We wanted to look at the role of lower pole anatomy to study clinical outcomes in patients treated for isolated lower pole stones (LPS) using retrograde intra renal surgery (RIRS), and also perform a review to look at the published literature on the influence of pelvicalyceal anatomy on success with RIRS. Data were prospectively collected (June 2013-June 2016) for all patients who underwent RIRS for LPS, and the imaging was then retrospectively reviewed to calculate the IPA, IL and IW using the Elbahnasy method. A systematic review was also conducted for all English language articles between January 2000 and April 2018, reporting on the impact of pelvicaliceal anatomy on RIRS. A total of 108 patients with LPS were included with a male to female ratio of 2:3 and a mean age of 54.7 years. The mean lower pole stone size was 9.3 mm (range 3-29 mm) and 102/108 (94.4%) patients were stone free (SF) at the end of their procedure. While steep IPA (< 30°), operative time duration and larger stone size were significant predictors of failure, the placement of ureteric access sheath, IW and IL did not influence treatment outcomes. Six studies (460 patients) met the inclusion criteria for our review. The IPA, IW, IL for failure ranged from 26° to 38°, 5.5-7 mm and 24-34 mm, respectively. The SFR ranged from 78 to 88% with a metaanalysis showing IPA as the most important predictor of treatment outcomes for LPS. Infundibular pelvic angle seems to be the most important predictor for the treatment of LPS using RIRS. Pelvicalyceal anatomy in conjunction with stone size and hardness seem to dictate the success, and decisions on the type of surgical interventions should reflect this.

Size is Not Everything That Matters: Preoperative CT Predictors of Stone Free After RIRS

OBJECTIVE

To define computed tomography (CT) predictors of residual fragments after retrograde intrarenal surgery (RIRS) for kidney stones up to 20 mm in patients never submitted to surgical procedures for stone removal.

METHODS

From August 2016 to August 2017, symptomatic adult patients with kidney stones less than 20 mm treated by RIRS had their pre- and postoperative CT prospectively evaluated in search for predictors of residual stone fragments. Stone size, stone volume, number of stones, stone density, and location were evaluated in preoperative CT and analyzed as predictors for residual stone fragments on 90 POD CT. Stone location was represented by the infundibulopelvic angle (IPA) measured for each stone on preoperative noncontrast CT using multiplanar reconstruction.

RESULTS

Ninety-two patients were successfully submitted to RIRS. Bilateral procedures were performed in 23 patients (25%) resulting in 115 renal units operated. Operative time was 54.5 ± 26.7 minutes (mean ± SD) and 96.7% (89/92) of the patients were discharged up to 12 hours after the procedure. Postoperative CT demonstrated stone-free in 86 of 115 (74.8%), 0-2 mm in 10 of 115 (8.7%), and > 2 mm residual fragments in 19 of 115 (16.5%) procedures. Logistic regression analysis revealed steep IPA was a predictor for any residual stone fragment after RIRS for kidney stones < 20 mm (P= .012). ROC curve showed that IPA < 41° was associated with a higher chance of residual fragments after RIRS.

CONCLUSION

IPA < 41° is associated with a higher chance of residual fragments after RIRS for kidney stones up to 20 mm.

The anatomy of the renal pyelocaliceal system studied by CTU

INTRODUCTION AND OBJECTIVES

Knowledge of the pyelocaliceal system anatomy is essential for the safe and successful performance of endourologic procedures. The purpose of this study was to provide a better understanding of the full three-dimensional pyelocaliceal system anatomy.

METHODS

Morphometric parameters of the three-dimensional reconstructions of computed tomography intravenous urography scans (n = 25 scans) were analyzed. Both kidneys were divided into three equal-sized segments (US: upper segment, MS: mid segment, LS: lower segment). Infundibular length (IL), infundibular width (IW), the number of calyces, and the transverse orientation in hours of a clock of each calyx as well as the dimension of the pyelum were determined.

RESULTS

The mean upper IL (n = 92) was longer than the middle (n = 154) and lower IL (n = 112) (30.6 ± 7.9 mm vs. 16.4 ± 7.7 mm vs. 16.0 ± 6.0 mm, respectively; P = < 0.0001). IW was significantly smaller in the MS [3.7 ± 1.9 mm], followed by the US [4.6 ± 1.9 mm], and the LS [4.9 ± 2.2] in the increasing order. No correlation was found between IL and IW (Pearson correlation coefficient = 0.1). The US calyces were predominantly orientated lateral (8-10 o'clock: 44.5%) and medial (2-4 o'clock: 30.5%), in the MS lateral (8-10 o'clock: 87.6%) and anterolateral in the LS (9-12 o'clock: 67.9%). 74% of the kidneys consisted of 6-8 calyces (mean 7.2 ± 1.4, range 4-10), with the majority of the calyces in the MS (3.1 ± 0.8) followed by the LS (2.24 ± 0.8), and US (1.8 ± 0.7). There were no statistical differences between the right and left kidneys in terms of IL (P = 0.112) and number of calyces (P = 0.685).

CONCLUSION

Anatomic differences between the three segments of the pyelocaliceal system in terms of IL, IW, calyces number, and orientation are seen and should be considered when performing an endourologic procedure.

Retrograde intrarenal surgery: An expanding role in treatment of urolithiasis

During the past 3 decades, the surgical management of kidney stones has undergone many technological advances and one is the development of the flexible ureteroscopy. The development of this instrument as well as ancillary equipment such as baskets, graspers, and others, and improvements in lithotripsy with Holmium: YAG laser have led to expand its indications with diagnostic and therapeutic management of medical issues of the upper urinary tract such as urolithiasis and urothelial tumors. The objective of this review is to describe its indications and results in the different scenarios for the treatment of urinary stones.

Steep Infundibulopelvic Angle as a New Risk Factor for Flexible Ureteroscope Damage and Complicated Postoperative Course

OBJECTIVE

The increasing number of flexible ureterorenoscopy (fURS) procedures, the fragility of devices, and their growing repair costs represent a substantial burden for urological departments worldwide. No risk factors of flexible ureteroscope damage have been identified so far. The objective of this study was to investigate the impact of infundibulopelvic angle (IPA) on device damage and on other intraoperative and postoperative factors such as length of hospital stay, surgical complications, stone-free rate (SFR), operation, and fluoroscopy time.

MATERIALS AND METHODS

In a retrospective monocentric study, IPA was measured based on intraoperative retrograde pyelography images taken during fURS. All procedures were conducted with modern reusable flexible ureteroscopes: Karl Storz Flex-X2 or Olympus URF-V. Statistical analysis was performed in RStudio (version 1.0.136) with the unpaired t-test and Mann-Whitney U test. Pearson correlation coefficient (Pearson's r) was measured whenever applicable.

RESULTS

In total, 381 fURS performed between September 2013 and March 2017 were analyzed: 260 (68.24%) for kidney stone operation and 121 (31.76%) for diagnostic purposes; of these, 38 (9.97%) devices were postoperatively deemed defective. IPA values were significantly steeper in cases with flexible ureteroscope damage compared to cases without damage (median 42.5 degrees vs 56.0, p < 0.001). Steeper IPA was significantly associated with the occurrence of Clavien-Dindo ≥2 complications (median 51.0 degrees vs 55.0, p = 0.005) as well as prolonged hospital stay (median 51.0 degrees vs 55.0, p = 0.014). No influence on SFR was observed (p > 0.05). IPA did not correlate with operation or fluoroscopy time.

CONCLUSIONS

Steep IPA can be considered the first risk factor predicting both flexible ureteroscope damage and an unfavorable postoperative course. A better understanding of damage mechanisms is the key for the proper indications to use costly single-use devices.

The R.I.R.S. scoring system: An innovative scoring system for predicting stone-free rate following retrograde intrarenal surgery

Background

To establish and internally validate an innovative R.I.R.S. scoring system that allows urologists to preoperatively estimate the stone-free rate (SFR) after retrograde intrarenal surgery (RIRS).

Methods

This study included 382 eligible samples from a total 573 patients who underwent RIRS from January 2014 to December 2016. Four reproducible factors in the R.I.R.S. scoring system, including renal stone density, inferior pole stone, renal infundibular length and stone burden, were measured based on preoperative computed tomography of urography to evaluate the possibility of stone clearance after RIRS.

Results

The median cumulative diameter of the stones was 14 mm, and the interquartile range was 10 to 21. The SFR on postoperative day 1 in the present cohort was 61.5% (235 of 382), and the final SFR after 1 month was 73.6% (281 of 382). We established an innovative scoring system to evaluate SFR after RIRS using four preoperative characteristics. The range of the R.I.R.S. scoring system was 4 to 10. The overall score showed a great significance of stone-free status (p < 0.001). The area under the receiver operating characteristic curve of the R.I.R.S. scoring system was 0.904.

Conclusions

The R.I.R.S. scoring system is associated with SFR after RIRS. This innovative scoring system can preoperatively assess treatment success after intrarenal surgery and can be used for preoperative surgical arrangement and comparisons of outcomes among different centers and within a center over time.

A prospective randomized comparison among SWL, PCNL and RIRS for lower calyceal stones less than 2 cm: a multicenter experience : A better understanding on the treatment options for lower pole stones

PURPOSE

To prospectively evaluate the efficacy and safety of RIRS, SWL and PCNL for lower calyceal stones sized 1-2 cm.

MATERIALS AND METHODS

Patients with a single lower calyceal stone with an evidence of a CT diameter between 1 and 2 cm were enrolled in this multicenter, randomized, unblinded, clinical trial study. Patients were randomized into three groups: group A: SWL (194 pts); group B: RIRS (207 pts); group C: PCNL (181 pts). Patients were evaluated with KUB radiography (US for uric acid stones) at day 10 and a CT scan after 3 months. The CONSORT 2010 statement was adhered to where possible. The collected data were analyzed.

RESULTS

The mean stone size was 13.78 mm in group A, 14.82 mm in group B and 15.23 mm in group C (p = 0.34). Group C compared to group B showed longer operative time [72.3 vs. 55.8 min (p = 0.082)], fluoroscopic time [175.6 vs. 31.8 min (p = 0.004)] and hospital stay [3.7 vs. 1.3 days (p = 0.039)]. The overall stone-free rate (SFR) was 61.8% for group A, 82.1% for group B and 87.3% for group C. The re-treatment rate was significantly higher in group A compared to the other two groups, 61.3% (p < 0.05). The auxiliary procedure rate was comparable for groups A and B and lower for group C (p < 0.05). The complication rate was 6.7, 14.5 and 19.3% for groups A, B and C, respectively.

CONCLUSIONS

RIRS and PCNL were more effective than SWL to obtain a better SFR and less auxiliary and re-treatment rate in single lower calyceal stone with a CT diameter between 1 and 2 cm. RIRS compared to PCNL offers the best outcome in terms of procedure length, radiation exposure and hospital stay. ISRCTN 55546280.

Retrograde intrarenal surgery for renal stones - Part 2

Retrograde intrarenal surgery (RIRS) has become an effective and safe treatment modality in the management of urinary system stone disease. Recent developments and innovations in the flexible ureterorenoscope and auxiliary equipment have made this procedure easier and more effective with increased success rates. RIRS can be used as a primary treatment in patients with renal stones smaller than 2 cm, prior unsuccessful shock wave lithotripsy, infundibular stenosis, renoureteral malformation, skeletal-muscular deformity, bleeding diathesis and obese patients. In the second part of this detailed review for RIRS, effect of stone composition on success rate, preoperative assessment of stone-free rate, the cost of this modality, education for RIRS, fluoroscopy use, the current role of RIRS in the treatment of various urolithiasis types and special conditions, and combined treatment methods are discussed with up-to-date literature.

Retrospective Analysis of Ultrasound-guided Flexible Ureteroscopy in the Management of Calyceal Diverticular Calculi

Background:

Percutaneous nephrolithotomy (PCNL) is the most widely recommended treatment for calyceal diverticular calculi, providing excellent stone-free results. However, its invasiveness is not negligible considering its major complication rates. Flexible ureteroscopy (FURS) is currently used to treat calyceal diverticula. However, the greatest drawback of FURS is locating the diverticulum since its neck is narrow and concealed. In such a case, the FURS procedure must be converted to PCNL. The aim of this study was to evaluate ultrasound-guided flexible ureteroscopy (UFURS) identifying diverticulum and the management of calyceal diverticular calculi.

Methods:

A retrospective analysis was conducted on 24 patients who had calyceal diverticular calculi. In all 12 patients in the UFURS group, direct FURS failed to find evidence of calyceal diverticula but were confirmed with imaging. The other 12 patients in the PCNL group received PCNL plus fulguration of the diverticular walls.

Results:

Puncture of calyceal diverticulum was successful in all 12 UFURS patients. Two patients in this group had postoperative residual calculi and two patients developed fever. In the PCNL group, percutaneous renal access and lithotomy were successful in all 12 patients. One patient in this group had residual calculi, one had perirenal hematoma, and two patients developed fever. No significant difference was found in the operating time (UFURS vs. PCNL, 91.8 ± 24.2 vs. 86.3 ± 18.7 min), stone-free rate (UFURS vs. PCNL, 9/12 vs. 10/12), and rate of successful lithotripsy (UFURS vs. PCNL, 10/12 vs. 11/12) between the two groups (all P > 0.05). Postoperative pain scores in the FURS group were significantly lower than that in the PCNL group (2.7 ± 1.2 vs. 6.2 ± 1.5, P < 0.05). Hospital stay in the UFURS group was significantly shorter than that in the PCNL group (3.4 ± 0.8 vs. 5.4 ± 1.0 days, P < 0.05). All patients were symptom-free following surgery (UFURS vs. PCNL, 10/10 vs. 12/12).

Conclusion:

Ultrasound-guided puncture facilitates identification of calyceal diverticula during FURS and improves the success rate of FURS surgery.

Flexible ureteroscopy for renal stone without preoperative ureteral stenting shows good prognosis

Purpose

To clarify the outcome of flexible ureteroscopy (fURS) for management of renal calculi without preoperative stenting.

Methods

A total of 171 patients who received 176 fURS procedures for unilateral renal stones were reviewed. All procedures were divided into two groups depending on whether they received ureteral stenting preoperatively. Baseline characteristics of patients, stone burden, operation time, stone-free rates, and complications were compared between both groups.

Results

Successful primary access to the renal pelvis was achieved in 104 of 114 (91.2%) patients without preoperative stenting, while all procedures with preoperative stenting (n = 62) were successfully performed. A total of 156 procedures were included for further data analysis (56 procedures in stenting group and 100 in non-stenting group). No significant differences was found regardless of a preoperative stent placement in terms of stone-free rate (73.2% with stenting vs. 71.0% without, P = 0.854), operative time (70.4 ± 32.8 with stenting vs. 70.2 ± 32.1 without, P = 0.969).

Conclusions

fURS for management of renal stone without preoperative ureteral stenting are associated with well outcome in short term follow-up. Our study may help patients and doctors to decide if an optional stent is placed or not.

Flexible Ureteroscopic Management of Horseshoe Kidney Renal Calculi

PURPOSE

To evaluate the clinical efficacy of flexible ureteroscope (F-URS) combined with holmium laser lithotripter in treating renal calculi in horseshoe kidney.

MATERIALS AND METHODS

From November 2010 to December 2013, the medical history and charts of sixteen patients (mean age 42.9 ± 11.6 years, range 26-66 years), including 13 males and 3 females were analyzed retrospectively. Mean stone burden was 29 ± 8 mm (range 17-42 mm2). Mean stone digitized surface area (DSA) was 321 ± 94 mm2 (range 180-538 mm2). Under spinal anesthesia in a modified lithotomy position with the head down, rigid ureteroscope was placed firstly into the ureter to reach the level of the pelvis, a zebra guide wire was inserted and following the removal of the rigid ureteroscope, an ureteral access sheath was positioned along the guide wire, then passed the URF P-5 flexible ureteroscope into the renal cavities over the guidewire. After locating the stones, holmium laser lithotripsy was performed.

RESULTS

The average operative time was 92 ± 16 minutes (range 74-127 min.). No major complications were encountered. Ten patients obtained stone-free status with one session, four obtained stone-free status after two sessions. Single session stone-free rate was 62.5%, overall stone-free rate was 87.5%. Two patients have small residual stones in the lower pole.

CONCLUSIONS

F-URS combined with holmium laser lithotripter and nitinol basket, is safe and effective in dealing with moderate stone diameter (<30 mm) in HSKs with high clearance rates and low complication rates.