Working tools in flexible ureterorenoscopy--influence on flow and deflection: what does matter?

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.

2022 Recommendations of the AFU Lithiasis Committee: Ureteroscopy and ureterorenoscopy

Technical advances, including miniaturization, have improved the deflection and optical performance of the ureteroscopes, and the availability of dedicated disposable devices have led to their increasing use for kidney and ureteral stone management. Ureterorenoscopy brings diagnostic evidence through the endoscopic description of stones and renal papillary abnormalities. Currently, intracorporeal lithotripsy during ureterorenoscopy is based on laser sources. Routine ureteral stenting is not necessary before ureterorenoscopy, especially because preoperative stenting for>30 days is considered as an independent risk factor of infection. Ureteral access sheaths allow the easy and repeated access to the upper urinary tract and thus facilitate ureterorenoscopy. Their use improves vision, decreases intrarenal pressure, and possibly reduces the operative time, but they may cause ureteral injury. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether or not the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis [EAU 2022]) and their adaptability to the French context.

Endourologic Procedures of the Upper Urinary Tract and the Effects on Intrarenal Pressure and Temperature

Introduction: Endourologic procedures, including ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL), are associated with an elevation in intrarenal pressures (IRPs) and irrigation temperatures. Recent research has focused on methods to reduce IRP and irrigation temperatures, with the ultimate goal to limit the consequences associated with these deviations. The purpose of our study is to provide a narrative review on the effects of endourologic procedures on pressure and temperature and provide recommendations to minimize these changes. Methods: A literature review was performed using PubMed. The search was limited to English human and nonhuman studies. Abstracts were reviewed for inclusion in our narrative review. Results: Human and animal models suggest that URS and PCNL are associated with peak IRPs above a "safe" threshold. Strategies to minimize pressures focus on minimizing irrigation flow into the upper tract and maximizing flow out of the system. High IRP has been associated with postoperative pain and infectious complications. Elevated irrigation temperatures are associated with high-power lasers during URS. Strategies to minimize irrigation temperatures focus on maximizing irrigation flow during laser activation and minimizing thermal energies associated with lithotripsy. Conclusions: Rises in pressure and irrigation temperatures associated with endourologic procedures are becoming increasingly recognized in the urologic community. Human studies examining "safe" thresholds for IRP and irrigation temperatures are limited. Temperature- and pressure-sensing technologies will aid in identifying the clinical consequences of elevated IRPs and irrigation temperatures, resulting in strategies to minimize them.

Best Practice in Interventional Management of Urolithiasis: An Update from the European Association of Urology Guidelines Panel for Urolithiasis 2022

PURPOSE

The European Association of Urology (EAU) has updated its guidelines on clinical best practice in urolithiasis for 2021. We therefore aimed to present a summary of best clinical practice in surgical intervention for patients with upper tract urolithiasis.

MATERIALS AND METHODS

The panel performed a comprehensive literature review of novel data up to May 2021. The guidelines were updated and a strength rating was given for each recommendation, graded using the modified Grading of Recommendations, Assessment, Development, and Evaluations methodology.

RESULTS

The choice of surgical intervention depends on stone characteristics, patient anatomy, comorbidities, and choice. For shockwave lithotripsy (SWL), the optimal shock frequency is 1.0-1.5 Hz. For ureteroscopy (URS), a postoperative stent is not needed in uncomplicated cases. Flexible URS is an alternative if percutaneous nephrolithotomy (PCNL) or SWL is contraindicated, even for stones >2 cm. For PCNL, prone and supine approaches are equally safe. For uncomplicated PCNL cases, a nephrostomy tube after PCNL is not necessary. Radiation exposure for endourological procedures should follow the as low as reasonably achievable principles.

CONCLUSIONS

This is a summary of the EAU urolithiasis guidelines on best clinical practice in interventional management of urolithiasis. The full guideline is available at https://uroweb.org/guidelines/urolithiasis.

PATIENT SUMMARY

The European Association of Urology has produced guidelines on the best management of kidney stones, which are summarised in this paper. Kidney stone disease is a common condition; computed tomography (CT) is increasingly used to diagnose it. The guidelines aim to decrease radiation exposure to patients by minimising the use of x-rays and CT scans. We detail specific advice around the common operations for kidney stones.

Determinants of outflow rate through the ureteral access sheath during flexible ureteroscopy: an experimental in vivo study in an anesthetized porcine model

To evaluate the effect of different ureteroscope positions, saline pumping frequency, laser fiber diameter and ureteral access sheath (UAS) on outflow rate during flexible ureteroscopy (fURS). This study was performed in an anesthetized porcine model. The fURS setup included a manual pumping system, a 9.5 Fr single used-digital flexible ureteroscope and a ureteral access sheath (UAS). Outflow was collected and measured from the UAS during 1 min in all experimental settings. The evaluated variables were the position of the ureteroscope, the pumping frequency (2 s, 3 s or 5 s), the diameter of the used UAS (12/14 Fr or 14/16 Fr) and laser fiber (200 μm or a 272 μm). Ureteroscope position in the lower calyx was associated with significantly lower outflow rate (p < 0.05). The use of the 14/16 Fr UAS resulted in improved flow in the renal pelvis and upper calyx (p < 0.05) but not in the lower calyx. The use of a 200 μm laser fiber only improved flow in the upper calyx and when a 14/16 Fr UAS was being used. Pumping frequency did not show a significant correlation with outflow rate. The ureteroscope positioning and UAS size were important determinants of outflow rate through the UAS during fURS, while laser fiber diameter had a limited effect. In the lower calyx the outflow was minimal and was not improved by using a larger UAS.

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.

Ureterorenoscopic lithotripsy for pediatric kidney stones using Holmium: YAG laser devices: 15 W versus 30 W

Introduction We aimed to compare the effectiveness of 15Watt (W) and 30 W Holmium: yttrium-aluminum-garnet (Ho: YAG) laser devices used in the treatment of pediatric kidney stones. Methods: Eighty-six consecutive pediatric patients who underwent retrograde intrarenal surgery between February 2010 and August 2020 were enrolled in the study. After exclusion criteria, the data of 79 children were evaluated retrospectively. Patients were divided into two groups according to the laser device power 15W (Group 15: N=30) and 30W (Group 30: N=49). The groups were compared according to demographic, stone feature, and clinical efficacy. Results The age, gender, height, weight, stone characteristics were similar between the groups. The mean operation time was shorter in Group 30. The stone-free rate after the first RIRS session (SF1) was 66.7% in Group 15 and 83.3% in Group 30. SF1 rate after the first RIRS procedure for 20 mm or larger kidney stones was found 0% in Group 15 and 62.5% in Group 30. However, there was no statistically significant difference between the two groups in terms of stone-free rate. Conclusion: In pediatric kidney stone treatment, 30 W Ho:YAG laser devices should be preferred as they shorten the operation time compared to 15 W devices and provide final stone-free with fewer procedures, especially in large kidney stones.

Comparison of irrigation flows between different irrigation methods for flexible ureteroscopy: An in vitro study

OBJECTIVE

To compare the irrigation flows between different irrigation methods for f-URS.

METHODS

We compared the automatic irrigation system Endoflow II to gravity-based irrigation, and gravity-based irrigation with pressure cuff. Irrigation pressures were set at 40 and 100cmH₂O. A LithoVue f-URS with a 3.6Fr working channel was used for the experiments. The f-URS was placed in straight alignment without active deflection on the operating table. For each irrigation pressure level, we evaluated the influence of the occupation of the working channel of the f-URS with an empty working channel, a 272μm laser fiber, a 1.9Fr nitinol basket. The outflow from f-URS was measured by the volume of irrigation fluid collected using a graduated glass at 1min, 2min, 3min and 5min.

RESULTS

Irrigations flows remained constant over the time for the Endoflow II and the gravity-based irrigation methods regardless of the irrigation pressure and setting. For the pressure cuff method, the irrigation flow remained constant only when the working channel was occupied either by the nitinol basket or the laser fiber. Irrigation flow with the Endoflow II were constantly higher than gravity-based irrigation methods. Irrigation flow significantly increased with increased irrigation pressure. In the presence of any instruments at any irrigation pressure, the flow decreased as the size of the instrument in the working channel increased.

CONCLUSIONS

Automatic irrigation system Endoflow II provided higher irrigation flows than gravity-based irrigation methods. The irrigation flow decreased as the size of the instrument in the working channel increased. Further studies conducted in vivo are needed to investigate if the differences found between irrigation methods result in higher intrarenal pressure during procedures.

LEVEL OF PROOF

4.

How to evaluate a flexible ureterorenoscope? Systematic mapping of existing evaluation methods

Objectives

The objective of this study was to identify, map and review scope‐related and user‐related parameters used to evaluate the quality of flexible ureterorenoscopes. Thereby identifying key items and variability in grading systems.

Methods

A literature search of four databases (MEDLINE [Ovid], EMBASE [Ovid], Web of Science, Google scholar and the Cochrane Library) was performed according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines encompassing articles published up to August 2020. A total of 2386 articles were screened.

Results

A total of 48 articles were included in this systematic scoping review. All studies had a prospective design. Five key items in the assessment of flexible ureterorenoscopy were distinguished: ‘Manoeuvrability’ (87.5%), ‘Optics’ (64.6%), ‘Irrigation’ (56.3%), ‘Handling’ (39.6%) and ‘Durability’ (35.4%). After regrouping, every key item could be divided into specific subcategories. However, the quality assessment showed a wide variation in denomination, method of measurement, circumstances of measurement, tools used during measurements, number of measurements performed, number of observers, and units of outcomes.

Conclusion

The research field regarding quality assessment of ureterorenoscopes is heterogeneous. In this systematic scoping review we identified five key parameters: Manoeuvrability, Optics, Irrigation, Handling and Durability, used to grade flexible ureterorenoscopes. However, within these categories we found a wide variety in terms of method of measurements. A standardised, uniform grading tool is required to assess and compare the quality of flexible ureterorenoscopes in the future.

Evaluation of a Novel Female Gender Flexible Ureteroscope: Comparison of Flow and Deflection to a Standard Flexible Ureteroscope

Introduction: The advent of single-use disposable flexible ureteroscopes allows for rapid prototyping of novel endoscopes. In this regard, we sought to develop a female-specific ureteroscope, with a shorter working length, to account for the female anatomy. We hypothesized that the shorter, female-specific single-use flexible ureteroscope would engender higher irrigation flow at a given pressure than that of the standard-length ureteroscope. Methods: An in vitro analysis of a standard 65 cm Dornier Axis™ ureteroscope and a shorter, 45 cm female-specific Dornier Axis ureteroscope was performed. All other aspects of the endoscopes were identical. Each ureteroscope was oriented vertically and connected to a Thermedx^® irrigation system to provide uniform pressurized flow. The average flow rate was computed over five, 2-minute periods at pressure settings of 50, 100, 150, and 200 mm Hg. Data were collected with the working channel unoccupied, after placement of a 200 μm (0.6F) holmium laser fiber and after passage of a 1.7F stone basket. The procedure was then repeated with the endoscopes at maximum deflection. Results: The female gender ureteroscope had significantly higher irrigation flow rates than the standard-length ureteroscope under all conditions by an average of 11% (p < 0.02). The highest average percent increase, 17% (p < 0.001), was seen with the 1.7F NGage^® basket in the working channel with the endoscope straight. The maximum angle of deflection was not significantly different between the female gender and standard ureteroscopes with an open working channel (314° vs 315°, p = 0.86), with the 1.7F NGage basket in place (314° vs 315°, p = 0.15), and with the 200 μm holmium laser in place (316° vs 309°, p = 0.09). Conclusions: A 45 cm female gender ureteroscope allows for a higher irrigation flow rate than the standard-length ureteroscope under all test conditions. There is no added benefit with regard to deflection capabilities.

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.

Change in irrigation flow through a flexible ureteroscope with various devices in the working channel: Comparison between an automatic irrigation pump and gravity-based irrigation

OBJECTIVES

To evaluate the change in the irrigation flow with various instruments in the working channel of a flexible ureteroscope by two automatic irrigation pumps and gravity-based irrigation in an ex vivo setting.

METHODS

We used two automatic irrigation pumps: the Endoflow II and the UROMAT Endoscopic Automatic System for Irrigation and gravity-based irrigation. A flexible ureteroscope was connected to an irrigation tube with a working channel. The other side of the irrigation tube was attached to each automatic irrigation pump, which was connected with a 2-L saline bag or to a 2-L saline bag directly in case of gravity pressure. The flow volume from the working channel was measured three times for 30 s at various irrigation pressure settings, both when the working channel was unoccupied and occupied with various instruments.

RESULTS

The irrigation flow steadily increased as the irrigation pressure in the automatic irrigation pumps increased and the saline position in gravity became higher (P < 0.05). However, the flow decreased as the size of the instrument in the working channel increased (P < 0.05). The efficiency of irrigation flow in gravity-based irrigation under the same pressure is significantly lower than one of two automatic irrigation pumps (P < 0.05). However, there was no significant difference in the efficiency of the irrigation flow between the Endoflow II and UROMAT Endoscopic Automatic System for Irrigation. The irrigation pressure setting needed to change to maintain adequate irrigation flow when using various working tools.

CONCLUSIONS

The efficiency of irrigation flow in gravity-based irrigation is significantly lower than one of two automatic irrigation pumps. The irrigation flow decreases as the size of the instrument in the working channel increases.

The Fluid Mechanics of Ureteroscope Irrigation

Purpose: To develop a physical understanding of ureterorenoscopy irrigation, we derive mathematical models from basic physical principles and compare these predictions with the results of benchtop experiments. Mathematical modeling can be used to understand the role of inlet pressure, tip deflection, the presence of working tools, geometric properties of the instruments used, and material properties of the irrigation fluid on resulting flow rate.

Materials and Methods: We develop theoretical models to describe irrigation flow in an idealized setup and compare with benchtop experiments for flow through a straight scope, a scope with a deflected tip, and a scope with a working tool inserted. The benchtop experiments were performed using Boston Scientific LithoVue ureteroscope and a variety of Boston Scientific working tools. Standard ureteroscope working channels have circular cross sections, but using theoretical models we investigate whether modifications to the cross-sectional geometry can enhance flow rates.

Results: The theoretical flow predictions are confirmed by experimental results. Tip deflection is shown to have a negligible effect on flow rate, but the presence of working tools decreases flow significantly (for a fixed driving pressure). Flow rate is predicted to improve when tools are placed at the edge of the channel, rather than the center, and modifying the cross-sectional shape from a circle to an ellipse can further increase flow rate.

Conclusions: A mathematical framework is formulated and shown to accurately predict the properties of ureteroscope irrigation flow. The theoretical approach has significant potential in quantifying irrigation flow and improving ureteroscope design.

Miniature ureteroscope distal tip designs for potential use in thulium fiber laser lithotripsy

Thulium fiber laser lithotripsy using smaller optical fibers may enable development of miniature ureteroscopes. Two ureteroscope distal tip prototypes were built and characterized. The first design was 4.5-French (Fr) [1.5-mm outer diameter (OD)], five channel tip, housing 200-μm inner diameter (ID) dedicated central channel for insertion of 100-μm core fibers and four surrounding channels, each with 1.5 Fr (510-μm ID) for instrumentation, irrigation, imaging, and illumination, respectively. The second design was 6.0-Fr (2.0-mm OD), three-dimensional printed tip with larger, hemispherical common working channel and separate detection port integrated with ring lighting. Standard instruments, including optical fibers, guidewires, and stone baskets, were inserted through working channels to demonstrate feasibility. Gravitational and manual pump-assisted saline irrigation rates were measured. Luminous intensity distribution curves (LIDCs) were modeled for both ring and conventional lighting designs. Imaging was conducted using 3000, 6000, and 10,000 pixel, miniature, flexible endoscopes with 0.4-, 0.6-, and 0.9-mm OD, to differentiate between urinary stones and ureter wall, for potential clinical application. The multichannel ureteroscope tip with 1.5-Fr working channel yielded a gravitational saline flow rate of 3.9  ±  0.2  mL  /  min compared to 31.3  ±  0.6  mL  /  min for standard (3.6 Fr) ureteroscope channel. Manual, pump-assisted irrigation increased flow rate to 32.5  ±  3.0  mL  /  min. The 6000 pixel, 0.6-mm OD, flexible endoscope provided a balance of clear differentiation between stones and ureter wall and sufficiently small OD. A ring lighting configuration provided more uniform illumination than conventional cross-lighting geometry as demonstrated by LIDCs. With further development, these miniature ureteroscope tip designs may be integrated into a fully functional ureteroscope to permit ureteral access with minimal trauma and improved patient safety and comfort.

Flexible ureteroscopy: technique, tips and tricks

During the last decades, the surgical management of kidney stones benefited of many technological advances and one of them is the development of flexible ureteroscopy (fURS). This tool, ancillary equipment such as graspers and baskets, and lithotripsy technique with Holmium:YAG laser underwent many improvements leading to a widening of its indications with diagnostic and therapeutic management of upper urinary tract pathologies such as urolithiasis and urothelial tumors. The objective of this review is to describe the surgical technique for fURS as well as tips and tricks for the treatment of renal stones.

In Vitro Comparison of Maximum Pressure Developed by Irrigation Systems in a Kidney Model

Purpose: To evaluate in vitro the maximum pressure generated in an artificial kidney model when people of different levels of strengths used various irrigation systems. Materials and Methods: Fifteen people were enrolled and divided into three groups based on their strengths. Individual strength was evaluated according to the maximum pressure each participant was able to achieve using an Encore™ Inflator. The irrigation systems evaluated were as follows: T-Flow™ Dual Port, Hiline™, continuous flow single action pumping system (SAPS™) with the system close and open, Irri-flo II™, a simple 60-mL syringe, and Peditrol™. Each irrigation system was connected to URF-V2 ureteroscope, which was inserted into an artificial kidney model. Each participant was asked to produce the maximum pressure possible with every irrigation device. Pressure was measured with the working channel (WC) empty, with a laser fiber, and a basket inside. Results: The highest pressure was achieved with the 60 mL-syringe system and the lowest with SAPS continuous version system (with continuous irrigation open), compared to the other irrigation devices (p < 0.0001). Irrespective of the irrigation system, there was a significant difference in the pressure between the WC empty and when occupied with the laser fiber or the basket inside it (p < 0.0001). The stratification between the groups showed that the most powerful group could produce the highest pressure in the kidney model with all the irrigation devices in almost any situation. The exception to this was the T-Flow system, which was the only device where no statistical differences were detected among these groups. Conclusion: The use of irrigation systems can often generate excessive pressure in an artificial kidney model, especially with an unoccupied WC of the ureteroscope. Depending on the strength of force applied, very high pressure can be generated by most irrigation devices irrespective of whether the scope is occupied or not.

Cost Analysis of Flexible Ureteroscope Repairs: Evaluation of 655 Procedures in a Community-Based Practice

INTRODUCTION

The frequency of flexible ureteroscopy has increased with the introduction of improved instrumentation. Ureteroscopes allow increased endoscopic access to the ureter and kidney. However, maintenance and repair of scopes may increase the total procedure expense.

METHODS

In 3 years (8/2011-7/2014), 655 flexible ureteroscopies were performed at a single-specialty, urology, ambulatory surgery center. Procedures were performed by 26 board-certified urologists using four Olympus URF P5 flexible ureteroscopes. The instruments were handled by a single team and sterilized through the STERIS System E1. Repairs were performed by the manufacturer on an as needed basis. Patient records were reviewed to determine the preoperative diagnosis, operative time, location and size of the stone, and use of laser or ureteral sheath. The occurrence, nature of flexible ureteroscope damage, and cost of repairs were evaluated.

RESULTS

Of the ureteroscopies performed, 78% was for the treatment of calculi (50.1% in the kidney). Mean stone size was 8.5 ± 0.2 mm, with larger stones (11 mm) located in the kidney. The flexible ureteroscope was advanced over a guidewire (88% of cases); a laser fiber was introduced in 70%, and a ureteral sheath was used in 13.4%. Mean procedure time was 40 minutes. The most common reasons for ureteroscope repair were cloudy lens (16 repairs) and broken optic fibers (9 repairs). There were 31 repairs during the study period (average 21 cases per repair). Flexible ureteroscopes were out of service for an average of 11 days per repair (range 3-20). The total cost of repairs was $233,150 or ∼$7521 per repair. The average repair cost per flexible ureteroscopy performed was $355.

CONCLUSIONS

Expenses associated with instrument repair can significantly impact a procedure's net revenue, thus efforts should be made to minimize instrument breakage. The expense of repairing a flexible ureteroscope per procedure can be significant and needs to be considered when pricing this procedure.

The truth about laser fiber diameters

OBJECTIVE

To measure the various diameters of laser fibers from various manufacturers and compare them with the advertised diameter.

METHODS

Fourteen different unused laser fibers from 6 leading manufacturers with advertised diameters of 200, 270, 272, 273, 365, and 400 μm were measured by light microscopy. The outer diameter (including the fiber coating, cladding, and core), cladding diameter (including the cladding and the fiber core), and core diameter were measured. Industry representatives of the manufacturers were interviewed about the diameter of their fibers.

RESULTS

For all fibers, the outer and cladding diameters differed significantly from the advertised diameter (P <.00001). The outer diameter, which is of most practical relevance for urologists, exhibited a median increase of 87.3% (range, 50.7%-116.7%). The outer, cladding, and core diameters of fibers with equivalent advertised diameters differed by up to 180, 100, and 78 μm, respectively. Some 200-μm fibers had larger outer diameters than the 270- to 273-μm fibers. All packaging material and all laser fibers lacked clear and precise fiber diameter information labels. Of 12 representatives interviewed, 8, 3, and 1 considered the advertised diameter to be the outer, the cladding, and the core diameter, respectively. Representatives within the same company frequently gave different answers.

CONCLUSION

This study suggests that, at present, there is a lack of uniformity between laser fiber manufacturers, and most of the information conveyed to urologists regarding laser fiber diameter may be incorrect. Because fibers larger than the advertised laser fibers are known to influence key interventional parameters, this misinformation can have surgical repercussions.

Thulium fiber laser lithotripsy in an in vitro ureter model

Using a validated in vitro ureter model for laser lithotripsy, the performance of an experimental thulium fiber laser (TFL) was studied and compared to the clinical gold standard holmium:YAG laser. The holmium laser (λ = 2120 nm) was operated with standard parameters of 600 mJ, 350 μs, 6 Hz, and 270-μm-core optical fiber. The TFL (λ=1908 nm) was operated with 35 mJ, 500 μs, 150 to 500 Hz, and a 100-μm-core fiber. Urinary stones (60% calcium oxalate monohydrate/40% calcium phosphate) of uniform mass and diameter (4 to 5 mm) were laser ablated with fibers through a flexible video-ureteroscope under saline irrigation with flow rates of 22.7 and 13.7 ml/ min for the TFL and holmium laser, respectively. The temperature 3 mm from the tube's center and 1 mm above the mesh sieve was measured by a thermocouple and recorded throughout each experiment for both lasers. Total laser and operation times were recorded once all stone fragments passed through a 1.5-mm sieve. The holmium laser time measured 167±41 s (n=12). TFL times measured 111±49, 39±11, and 23±4 s, for pulse rates of 150, 300, and 500 Hz, respectively (n=12 each). Mean peak saline irrigation temperatures reached 24±1°C for holmium, and 33±3°C, 33±7°C, and 39±6°C, for TFL at pulse rates of 150, 300, and 500 Hz, respectively. To avoid thermal buildup and provide a sufficient safety margin, TFL lithotripsy should be performed with pulse rates below 500 Hz and/or increased saline irrigation rates. The TFL rapidly fragmented kidney stones due in part to its high pulse rate, high power density, high average power, and observation of reduced stone retropulsion and may provide a clinical alternative to the conventional holmium laser for lithotripsy.

Update on lasers in urology 2014: current assessment on holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripter settings and laser fibers

PURPOSE

The purpose of the study was to review the existing literature on holmium:yttrium-aluminum-garnet laser lithotripsy regarding lithotripter settings and laser fibers.

METHODS

An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here.

RESULTS

We examine how the choice of lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the lithotripter settings' influence on tip degradation.

CONCLUSIONS

Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.

Minimally invasive surgical instruments with an accessory channel capable of integrating fibre-optic cable for optical biopsy: A review of the state of the art

This review article provides a comprehensive overview and classification of minimally invasive surgical instruments with an accessory channel incorporating fibreoptics or another auxiliary device for various purposes. More specifically, this review was performed with the focus on the newly emerging field of optical biopsy, its objective being to discuss primarily the instruments capable of carrying out the optical biopsy and subsequent tissue resection. Instruments housing the fibreoptics for other uses, as well as instruments with an accessory channel capable of housing the fibreoptics instead of their original auxiliary device after relevant design modifications, supplement the review. The entire Espacenet and Scopus databases were searched, yielding numerous patents and articles on conceptual and existing instruments satisfying the criteria. The instruments were categorised based on the function the fibreoptics or the auxiliary device serves. On the basis of their geometrical placement with respect to the tissue resector or manipulator, the subcategories were further defined. This subdivision was used to identify the feasibility of performing the optical biopsy and the tissue resection in an accurate and successive fashion. In general, the existing concepts or instruments are regarded as limited with regard to such a functionality, either due to the placement of their accessory channel with or without the fibreoptics or due to the operational restrictions of their tissue manipulators. A novel opto-mechanical biopsy harvester, currently under development at Delft University of Technology, is suggested as a promising alternative, ensuring a fast and accurate succession of the optical and the mechanical biopsies of a flat superficial tissue.

Pushing the boundaries of ureteroscopy: current status and future perspectives

Substantial advances in ureteroscopy have resulted in the incorporation of this procedure into routine urological practice in many centres worldwide. Subsequently, an abundance of clinical data and technological progression have enabled the development of novel solutions that have increased the efficacy of ureteroscopy, and reduced associated morbidity and costs. In addition the indications for this retrograde approach have been expanded, and pyelocalyceal diverticulum, infundibular stenosis, urolithiasis in pregnant women or in patients with urinary diversions, as well as upper urinary tract tumours can now be managed using this methodology. New endoscopes are continuously developed, with different manufacturers choosing various technical solutions to further increase the efficacy and safety-and sometimes decrease costs-of ureteroscopy, including miniaturization, inclusion of digital optical systems and dual working channels, and the introduction of disposable apparatus. The holmium laser, currently the most-versatile energy source available, enables tissue incision, tumour ablation, and intracorporeal lithotripsy. Modern ancillary instruments are diverse, flexible, and durable, and novel devices used in daily clinical practice can minimize ascendant migration of stone fragments and, therefore, decrease the failure rate of the retrograde ureteroscopic approach. However, the peak of ureteroscopy evolution seems to remain distant, with further improvement of endoscopes and ancillary instruments, and robot-assisted ureteroscopy representing only some of the areas in which future developments are possible.

[Ureteroscopy: is it the best?]

Over the last 40 years the treatment of urolithiasis passed from open surgical therapies to minimally invasive approaches. From the introduction of the first ureteroscopes in '80s many technological improvements allowed to reduce endourological instruments' size, ensuring in the meanwhile an increasingly high success rate in the resolution of the urolithiasis. The purpose of the study is to review the current role of the ureteroscopy(URS) in the treatment of urinary stones. A non-systematic review was performed considering the most recent Guidelines and results from Literature. The results confirm that, considering ureteral calculi, the stone-free rate (SFR) for URS is significantly higher than for ESWL in the treatment of distal ureteral stones <10 mm and >10 mm. Endoscopy has a first-line role also in the treatment of proximal ureteral stones >10 mm, together with ESWL. Retreatment rate and ancillary procedures are also lower in patients treated with URS, despite it is more invasive if compared with ESWL. Recent data are available in Literature about the treatment of nephrolithiasis with Retrograde Intra-Renal Surgery (RIRS). RIRS is the first-line treatment, together with ESWL, for stones <20 mm, and second choice for stones >20 mm. However, for large renal stones the role of RIRS is still being discussed. In conclusion, the majority of urinary stones can be treated by rigid or flexible URS. Further studies are required to clarify the role of endoscopy in the treatment of large stones, especially if compared to percutaneous approaches.

Managing caliceal stones

The natural course of untreated asymptomatic caliceal calculi has not been clearly defined, especially in terms of disease progression, and the indications for and outcomes of surgical intervention are not precise. Caliceal stones may remain asymptomatic but, in case of migration, ureteral calculi can cause acute ureteric colic with severe complications. The decision for an active treatment of caliceal calculi is based on stone composition, stone size and symptoms. Extracorporal shock-wave lithotripsy (ESWL) has a low complication rate and is recommended by the current guidelines of the European Association of Urology as a first-line therapy for the treatment of caliceal stones <2 cm in diameter. However, immediate stone removal is not achieved with ESWL. The primary stone-free rates (SFR) after ESWL depend on stone site and composition and, especially for lower pole calculi, the SFR differ widely from other caliceal stones. Minimally-invasive procedures including percutaneous nephrolithotomy and ureteroscopy are alternatives for the treatment of caliceal stones, associated with low morbidity and high primary SFR when performed in centers of excellence.

Superiority of the EF-120-00-3F biopsy forceps in the histopathological evaluation of upper urinary tract specimens

PURPOSE

The purpose of this study was to analyze the efficacy of two different biopsy forceps with respect to their functionality and quality for histological assessment of upper urinary tract biopsies.

METHODS

We compared flow rates, active deflection angle and histological quality of specimens taken from upper urinary tract biopsies of 40 consecutively treated patients between October 2011 and October 2012. Two different biopsy forceps [group A = 20 patients: "Piranha (®) " (Boston Scientific, Natick, USA) versus group B = 20 patients: "EF-120-00-3F" (Euromedical GmbH, Siegsdorf, GER)] were assessed.

RESULTS

The specimens obtained with the "EF-120-00-3F" were superior in terms of tissue preservation such as intact urothelium/tissue fragmentation and the prevention of artifacts due to tissue compression (existence of artifacts/nucleus evaluation). Furthermore, due to superiority of tissue preservation, tissues obtained with the "EF-120-00-3F" showed better tissue orientation in the sense of anatomic evaluation of invasion and deep layer involvement. Irrigation flow rates did not differ significantly while deflection angle was more impaired with the "Piranha" biopsy forceps. No difference was observed with the handling of both biopsy forceps.

CONCLUSIONS

We conclude that the "EF-120-00-3F" biopsy forceps represent a valuable modification of antegradely insertable instruments that qualifies for improved and correct staging as well as diagnosis of upper urinary specimens in comparison with standard biopsy forcipes.

A new era: performance and limitations of the latest models of flexible ureteroscopes

OBJECTIVE

To comparatively study 3 of the latest models of flexible ureteroscopes using both subjective and objective parameters.

MATERIALS AND METHODS

Three models of flexible ureteroscopes (Karl Storz Flex-Xc, Olympus URF-Vo, and Wolf Cobra) were evaluated during 90 procedures. For each model, 20 procedures were therapeutic for pyelocaliceal lithiasis and 10 were diagnostic. The maneuverability and visibility were scored and compared, and the irrigation flow and maximal deflection were measured in an ex vivo setting, with an empty working channel and with accessory instruments in place. Instrument durability was also reviewed.

RESULTS

All models demonstrated good maneuverability, with a slight advantage for the Flex-Xc. During the diagnostic procedures, failure to access the entire pyelocaliceal system occurred in 2 cases with the URF-Vo, both because of a thin caliceal infundibulum, and in 1 case with the Cobra, because of complex caliceal architecture. Regarding visibility, although the performance of the digital models was relatively similar, the fiberoptic Cobra achieved a lower score. Loss of deflection and irrigation when using the various ancillary instruments was similar for all 3 endoscopes, but the Cobra offered supplementary flow through a secondary channel. The mean deflection loss was 5% for the URF-Vo, 9% for the Flex-Xc, and 10% for the Cobra. The visual quality of the 2 digital models remained unchanged during the study; however, in the fiberoptic ureteroscope, 58 optic fibers were broken.

CONCLUSION

The latest models of flexible ureteroscopes have proved to be effective instruments for upper urinary tract endoscopic interventions. There is still room for improvement, already made possible by the technological advances.

A dual-channel flexible ureteroscope: evaluation of deflection, flow, illumination, and optics

BACKGROUND AND PURPOSE

Despite the evolution and progressive improvements of ureteroscopes, problems related to visibility and maneuverability can still hinder the goals of surgical intervention. We evaluate the attributes of a dual-channel flexible ureteroscope compared with a single-channel device and discuss the implications for expanded techniques afforded by this new technology.

MATERIALS AND METHODS

In vitro measurements of active deflection, irrigant flow through the working channel, luminescence, and optical resolution were performed between the single-channel Wolf Viper and the dual-channel Wolf Cobra ureteroscopes. Characteristics were obtained with the working channels both empty and with combinations of a 200 μ holmium aser fiber, 3.0F biopsy forceps, and 1.5F, 2.4F, and 2.8F nitinol basket. Luminescence from each scope was measured using a commercial luminometer. Three blinded physicians rated the optical resolution captured electronically using a standard test image.

RESULTS

The single-channel scope has improved upward deflection both empty and with all but the largest single tools, with an improved range of 4 to 15 degrees. The dual-channel scope has superior downward deflection across all comparisons (average increase of 24.5 degrees) and superior upward deflection with large or multiple instruments in the working channel. Baseline flows through each individual-channel of the dual-channel scope were slower than the larger single-channel ureteroscope. Because flow can be provided through a dedicated port in the dual-channel configuration, however, overall flow, depending on instrumentation, can be up to 37 times faster than the single-channel (range 1.5-37×). Optical resolution and luminescence are comparable between the two scopes.

CONCLUSION

The dual-channel flexible ureteroscope provides similar deflection characteristics to the current single-channel scope. Deflection and flow characteristics are superior, however, when larger or multiple simultaneous instruments are used in the working channel. These benefits may facilitate the development and implementation of novel endoscopic procedures.

Endoscopic management of upper tract transitional cell carcinoma

Upper urinary tract transitional cell carcinoma (TCC) accounts for up to 10% of cases of neoplasm of the upper urinary tract. The “gold standard” management of upper tract TCC is nephroureterectomy. Technological innovations, miniaturisations and increased availability of energy sources such as Holmium laser fibers have improved the armamentarium of endoscopic management of upper tract TCC. Endoscopic management of upper tract TCC includes the percutaneous (antegrade) and retrograde approaches. Modern flexible ureterorenoscopy allows retrograde approach to small (<1.5cm), low grade and noninvasive tumors, which is inaccessible to standard rigid ureteroscopes without breaching the urothelial barrier. In patients with large tumors or in whom retrograde access is difficult, the percutaneous approach to the renal pelvis, although more invasive, provides an alternative access and control. Both retrograde and percutaneous approaches allow instillation of various chemotherapeutic agents. Careful selection of patients is the key point in the successful endoscopic management of upper tract TCC. Patient selection is based on tumor size, grade and multifocality and other patient factors such as comorbidities, single kidney, post kidney transplant and patient choice. Both motivation and compliance of patients are needed for long-term successes. However, until large randomized trials with long term follow-up are available, endoscopic management of upper tract TCC should be reserved for only selected group of patients. This review summarizes the current techniques, indications, contraindications and outcomes of endoscopic management of UTTCC and the key published data.

Effectiveness of single flexible ureteroscopy for multiple renal calculi

PURPOSE

To assess effectiveness of flexible ureteroscopy (fURS) in patients not with simple but with multiple unilateral renal stones.

PATIENTS AND METHODS

A database analysis was performed to identify patients with multiple unilateral intrarenal stones. Patients were treated using an 8.8F flexible ureteroscope. Patients were considered stone free if no residual stones were seen endoscopically and radiographically after the procedure. The efficiency and the safety of the procedures were analyzed.

RESULTS

Between 2006 and 2008, 1054 ureteroscopic procedures were performed in our department; 125 patients met the inclusion criteria. Holmium:yttrium-aluminum-garnet laser lithotripsy was necessary in 41 (32.8%) patients. The mean stone size was 11.93 ± 8.2 mm, with a mean stone burden of 83.7 ± 67.66 mm(2). The mean number of stones was 3.59 ± 3.57. Twenty-six (20.8%) patients had a stone burden ≥ 100 mm(2), and 99 (79.2%) a stone burden <100 mm(2). The overall stone-free rate after a single procedure of fURS was 74.4%. In the remaining 32 patients with residual stones, the mean stone burden dropped from 123.24 ± 84.36 mm(2) to 56.28 ± 52.53 mm(2). The stone-free rate in patients with a stone burden ≥ 100 mm(2) was 65.4% and 79.5% in patients with a stone burden < 100 mm(2), respectively. Complications have been recorded in seven (5.6%) patients, including urinary tract infection in four, ureteral perforation in one, and hematuria in two patients. No major complications occurred. All patients were treated conservatively.

CONCLUSIONS

fURS is an effective treatment option in patients with multiple unilateral renal stones. Single procedure stone-free rates are high with a low rate of only minor complications.

Instrumentation in endourology

Success with endourological procedures requires expertise and instrumentation. This review focuses on the instrumentation required for ureteroscopy and percutaneous nephrolithotomy, and provides a critical assessment of in vitro and clinical studies that have evaluated the comparative effectiveness of these medical devices.

Small-diameter nitinol stone baskets: radial dilation force and dynamics of opening

PURPOSE

To evaluate the radial dilation force and basket opening dynamics of three small (<1.5F) stone baskets.

MATERIALS AND METHODS

Boston Scientific OptiFlex (1.3F), Cook N-Circle Nitinol Tipless Stone Extractor (1.5F), and Sacred Heart Medical Halo (1.5F) baskets were tested for radial dilation force in 10 repetitions using a floating block atop a stationary block secured to a digital scale. The floating block, attached to a plastic frame and base, pressed down on the scale to measure the radial dilation of the open basket while being passed through the cylindrical opening between the blocks. These same baskets were tested in triplicate for basket width in 0.5- to 2-mm length increments using a mechanical caliper under optical light microscope visualization to evaluate the linearity of basket opening and length at which target basket width (5 mm) was reached.

RESULTS

The Sacred Heart Medical Halo had the best radial dilation (2.97 ± 0.22 g), followed by the Cook N-Circle (1.29 ± 0.04 g), and finally Boston Scientific OptiFlex (1.19 ± 0.12 g). The N-Circle was the only basket to exhibit linear opening, while the Halo exhibited an exponential curve. The OptiFlex exhibited a polynomial curve, with linear opening across the midrange of the basket length. From these curve equations, the target basket width (5 mm) was calculated. The N-Circle and the OptiFlex reached the target basket width at a basket length of 9.4 mm and 9.6 mm, respectively. The Halo reached the target basket width at a basket length of 11.5 mm.

CONCLUSIONS

The radial dilation force differs significantly among commercial baskets and may affect ureteral stone extraction. Linear basket opening may provide the physician more control in stone retrieval.