Digital ureteroscopes: technology update

Recent advances in the treatment of renal stones using flexible ureteroscopys

Upper urinary tract stones are a common urological disease that can be treated by flexible ureteroscopy (FURS) through the natural urinary tract, in addition to extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy. The advantages of FURS are less trauma, faster recovery, and fewer complications, while its disadvantages include poor results of lithotripsy and stone extraction when dealing with larger stones, and prolonged operation time. Over the last two decades, the emergence of new technologies such as FURS combined with negative pressure suction, robot-assisted FURS, and artificially intelligent FURS, coupled with improvements in laser technology (the use of thulium fiber lasers and the invention of single-use flexible ureteroscopes (su-fURS) suitable for primary level application, have significantly increased the global adoption of FURS. This surge in usage holds a promising future in clinical application, benefiting a growing number of patients with renal calculi. Accompanied by changes in technical concepts and therapeutic modalities, the scope of indications for FURS is broadening, positioning it as a potential primary choice for urolithiasis treatment in the future. This review outlines the progress in employing FURS for the treatment of renal calculi in order to generate insights for further research.

Being all-seeing gymnast within kidney cavity: analysis of the optical and flexibility characteristics trends of 61 flexible ureteroscopes over four decades

The purpose of this review is to analyze the trend in optical features and flexibility changes of flexible ureteroscopes over the past decades, and determine the correlation of individual parameters with release period as well as with dimensional parameters. Flexible ureteroscopes mentioned in the literature or those commercially available were searched. To minimize the search bias, the instruments were grouped by release date time-periods of < 2000 year, 2000-2009, 2010-2019, and 2020 onwards. The final review included only those instrument models for which data on minimum and maximum depth of field, field of view, direction of view, and deflection degree had been determined. The correlation among features investigated as well as with release period was also determined. 61 models of flexible ureteroscopes (27 fibreoptic and 34 digital scopes) were included. Among the different features investigated among fiberoptic endoscopes, minimum depth of field positively and negatively correlated with channel size and field of view, respectively, whereas maximum depth of view and field of view positively correlated with overall shaft and deflection degree, respectively. Up and down deflection strongly correlated with each other and both were negatively proportional to the distal tip size. For the digital endoscopes, minimum depth of field negatively and positively correlated with distal tip size and working length, respectively. Maximum depth of field positively correlated with field of view, whereas the latter was negatively proportional to the overall shaft. As for the fiberoptic counterparts, up and down deflection strongly correlated with each other. Field of view, up and down deflection of fiberoptic flexible ureteroscopes, were significantly increased among fiberoptic and digital endoscopes over decades. As flexible ureteroscopy technology has evolved, there has been a trend towards increasing field of view with up and down deflection. Given the importance of scope ergonomics, one aspect of this popularity is the improvement of optical characteristics and deflection degree, which significantly correlates with the release period.

Single use flexible ureteroscopes: Current status and future directions

Introduction

Single use ureteroscopes are a technological innovation that have become available in the past decade and gained increased popularity. To this end, there are now an increasing number of both benchside and clinical studies reporting outcomes associated with their use. Our aim was to deliver a narrative review in order to provide an overview of this new technology.

Methods

A narrative review was performed to gain overview of the history of the technology's development, equipment specifications and to highlight potential advantages and disadvantages.

Results

Findings from preclinical studies highlight potenial advantages in terms of the design of single use ureteroscopes such as the lower weight and more recent modifications such as pressure control. However, concerns regarding plastic waste and environmental impact still remain unanswered. Clinical studies reveal them to have a non inferior status for outcomes such as stone free rate. However, the volume of evidence, especially in terms of randomised trials remains limited. From a cost perspective, study conclusions are still conflicting and centres are recommended to perform their own micro cost analyses.

Conclusions

Most clinical outcomes for single use ureteroscopes currently match those achieved by reusable ureteroscopes but the data pool is still limited. Areas of continued debate include their environmental impact and cost efficiency.

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.

Single-use versus conventional reusable flexible ureteroscopes - an evaluation of the functional parameters

The purpose of single-use flexible ureteroscopes (su-fURS) was to overcome the limitations of conventional reusable ureteroscopes in terms of maneuverability and maintenance. We aimed to perform a systematic literature review on available su-fURS performance versus conventional reusable fURS focusing on clinical data. A systematic research using Pubmed was performed evaluating single-use fURS and reusable fURS in urinary tract stone disease, including prospective assessments and case series. This review aimed to provide an overview of single-use and disposable flexible ureteroscopes and to examine and compare their capabilities (deflection, irrigation, optical properties). We included 11 studies, where the single-use fURS were compared to the reusable fURS. The studies with single-use ureteroscopes included data on LithoVue (Boston Scientific), The Uscope UE3022 (Pusen, Zhuhai, China), NeoFlex-Flexible, (Neoscope Inc San Jose, CA), 23 YC-FR-A (Shaogang). For reusable ureteroscopes, data were included on three models, two digital (Karl Storz Flex-XC and Olympus URF-Vo) and one fiber optic (Wolf-Cobra). There were no significant differences in stone-free rate, procedure duration, or functional capabilities between single-use fURS and reusable fURS. The systematic literature review analyzed operative time, functional capabilities, stone-free rates, and postoperative complications of the ureteroscopes, and a special chapter about renal abnormalities to emphasize that they are a good choice having a high proportion of stone-free rates and few risks, particularly in treating difficult-to-access calculi. Single-use fURS demonstrate a comparable efficacy with reusable fURS in resolving renal lithiasis. Further studies on clinical efficacy are needed to determine whether single-use fURS will reliably replace its reusable counterpart.

Innovations in Kidney Stone Removal

Urolithiasis is a common clinical condition, and surgical treatment is performed with different minimally invasive procedures, such as ureteroscopy, shockwave lithotripsy and percutaneous nephrolithotomy. Although the transition from open surgery to endourological procedures to treat this condition has been a paradigm shift, ongoing technological advancements have permitted further improvement of clinical outcomes with the development of modern equipment. Such innovations in kidney stone removal are new lasers, modern ureteroscopes, development of applications and training systems utilizing three-dimensional models, artificial intelligence and virtual reality, implementation of robotic systems, sheaths connected to vacuum devices and new types of lithotripters. Innovations in kidney stone removal have led to an exciting new era of endourological options for patients and clinicians alike.

The role of endoscopic management and adjuvant topical therapy for upper tract urothelial cancer

Upper tract urothelial carcinoma (UTUC) has traditionally been managed with radical nephroureterectomy, and while this approach remains the gold standard for high-risk disease, endoscopic, kidney-sparing management has increasingly been adopted for low-risk disease as it preserves kidney function without compromising oncologic outcomes. Ureteroscopy and percutaneous renal access not only provide diagnoses by tumor visualization and biopsy, but also enable treatment with electrocautery or laser ablation. Several modalities exist for laser ablative treatments including thulium:YAG, neodymium:YAG, holmium:YAG, and combinations of the preceding. Furthermore, due to high recurrence rates after endoscopic management, adjuvant intracavitary instillation of various agents such as mitomycin C and bacillus Calmette-Guerin have been used given benefits seen in non-muscle invasive urothelial bladder cancer. Other formulations also being studied include gemcitabine, anthracyclines, and immunotherapies. More recently, Jelmyto, a mitomycin reverse thermal gel, has been developed to allow for adequate drug delivery time and potency since urine flow could otherwise dilute and washout topical therapy. In this article, the authors review techniques, indications, best practices, and areas of current investigation in endoscopic management and adjuvant topical therapy for UTUC.

Hybrid flexible ureteroscopy strategy in the management of renal stones - a narrative review

The introduction of single-use flexible ureteroscopes (suFURSs) in daily practice tends to overcome the main limitations of reusable ureteroscopes (reFURSs), in terms of high acquisition costs, maintenance, breakages and repairing costs, reprocessing and sterilization, as retrograde intrarenal surgery (RIRS) is promoted as first-line treatment of renal stones in most cases. A hybrid strategy implies having both instruments in the armamentarium of endourology and choosing the best strategy for cost-efficiency and protecting expensive reusable instruments in selected high-risk for breakage cases such as large stones of the inferior calyx, a steep infundibulopelvic angle or narrow infundibulum, or abnormal anatomy as in horseshoe and ectopic kidney. In terms of safety and efficiency, data present suFURSs as a safe alternative considering operating time, stone-free, and complication rates. An important aspect is highlighted by several authors about reusable instrument disinfection as various pathogens are still detected after proper sterilization. This comprehensive narrative review aims to analyze available data comparing suFURSs and reFURSs, considering economic, technical, and operative aspects of the two types of instruments, as well as the strategy of adopting a hybrid approach to selecting the most appropriate flexible ureteroscope in each case.

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.

Comparative investigation of reusable and single-use flexible endoscopes for urological interventions

In order to evaluate the technical adaptability of a type of disposable endoscope compared to reusable flexible endoscopes, in vitro and in vivo studies were conducted. A disposable digital ureteroscope ("chip on tip") and two reusable endoscopes were investigated with respect to spatial resolution, geometric distortion in air and water the maximum. Additionally, the clinical performance of the disposable device was tested during clinical procedures (n = 20). The disposable endoscope showed an optical resolution of 6.72 lines/mm at 10 mm distance, similar to the other devices. In comparison, the disposable endoscope showed a barrel-shaped image distortion in air of -24.2%, which is in the middle range, but was best under water (-8.6%). The bendability of 297° (275 µm fiber) and 316° (empty channel, 1.5 F basket) and the maximum irrigation (1 m: 58.1 ml/min, 2 m: 91.9 ml/min) were convincing. Clinically the maneuverability was very good in (13/20), good or satisfactory in (7/20). Visibility was evaluated as very good in (11/20), just in (1/20) either satisfactory or sufficient. The consistency of visibility was not affected in (19/20). In all cases there were no adverse events. The technical examination and clinical application of the disposable endoscope are of equal quality compared to reusable devices. Disposable endoscopes can be an alternative to reusable devices, but economic aspects such as reduction of repair costs, sterilization effort and additional waste must be taken into account.

Update on Surgical Management of Pediatric Urolithiasis

Urolithiasis has always been a fascinating disease, even more so in children. There are many intriguing facets to this pathology. This article is a nonsystematic review to provide an update on the surgical management of pediatric urolithiasis. It highlights the pros and cons of various minimally invasive surgical options such as extracorporeal shockwave lithotripsy (ESWL), retrograde intrarenal surgery (RIRS), percutaneous nephrolithotomy (PCNL), laparoscopy, and robotics. This article also describes the various intracorporeal disintegration technologies available to fragment the stone, including the newer advancements in laser technology. It also emphasizes the cost considerations especially with reference to the emerging economies. Thus, this manuscript guides how to select the least-invasive option for an individual patient, considering age and gender; stone size, location, and composition; and facilities and expertise available.

Thulium fiber laser ablation of kidney stones using an automated, vibrating fiber

Our preliminary study investigates an automated, vibrating fiber optic tip for dusting of kidney stones during thulium fiber laser (TFL) lithotripsy. A (0.75-mm diameter and 5-mm length) magnetic bead was attached to the fiber jacket, centered 2 cm from distal fiber tip. A solenoid was placed parallel to the fiber with a 0.5-mm gap between solenoid and magnetic bead on fiber. The solenoid was used to create a magnetic force on the bead, inducing fiber vibration. Calibration tests for fiber motion in both air and water were performed. The ablation crater characteristics (surface area, volume, depth, and major/minor axis) of uric acid stones were measured using optical coherence tomography, after delivery of 1500 TFL pulses at 1908 nm, 33 mJ, 500  μs, and up to 300 Hz, through 50-, 100-, and 150-μm-core fibers. The resonant frequency was dependent on fiber diameter and rigidity, with a cutoff pivot point for optimum vibration amplitude at 4 cm. Maximum fiber displacement is about 1 mm in water and 4 mm in air. For 50-, 100-, and 150-μm-core fibers, ablated surface area averaged 1.7, 1.7, and 2.8 times greater with vibrating fiber than fixed fiber, respectively. For these fibers, ablation volume averaged 1.1, 1.5, and 1.1 times greater with vibrating fiber than fixed fiber, given a fixed energy per pulse, respectively. Our preliminary study demonstrates the functionality of an automated, vibrating fiber system for stone "dusting," with significantly larger surface area but similar ablation volumes as a fixed fiber. Future studies will focus on optimization of fiber parameters (especially displacement) and miniaturization of system components to facilitate integration into ureteroscopes.

Interventional radiology-operated endoscopy using the LithoVue disposable endoscope: Approach, technical success, clinical outcomes, and complications

Purpose:

To report the approach, technical success, clinical outcomes, and complications of interventional radiology-operated endoscopy using the LithoVue disposable endoscope.

Materials and Methods:

12 patients, 6 (50%) males and 6 (50%) females, underwent interventional radiology-operated endoscopy using the LithoVue disposable endoscope between April 2016 and August 2017. Presenting complaint, reason for endoscopic evaluation, technical success, clinical success, procedure time, fluoroscopy time, hospital length of stay, and complications were recorded.

Results:

Interventional radiology-operated endoscopy using the LithoVue disposable endoscope was used in 8 (67%) biliary, 2 (16.5%) urologic, and 2 (16.5%) gastrointestinal procedures. Five (42%) patients required endoscopy to locate an ostium that could not be cannulated under fluoroscopy. Five (42%) patients had a biliary-enteric anastomosis with postoperative anatomy of the bowel which precluded endoscopic retrograde cholangiopancreatography and underwent endoscopy for removal of calculi. One (8%) patient underwent treatment of a stricture and one (8%) underwent biopsy. Technical success was 92% (11/12). Clinical success was 83% (10/12). Two complications, a perinephric hematoma and sepsis, occurred.

Conclusion:

Disposable endoscopes, including the LithoVue, may be used in a variety of procedures to improve patient care and limit fluoroscopy.

Single-use versus reusable ureterorenoscopes for retrograde intrarenal surgery (RIRS): systematic comparative analysis of physical and optical properties in three different devices

INTRODUCTION

Retrograde intrarenal surgery (RIRS) represents a standard option for kidney stone removal. However, RIRS is considered a cost-intensive procedure. Single-use flexible ureterorenoscopes have been introduced to improve budget predictability in RIRS. We assessed differences in physical and optical properties of single-use devices compared to standard reusable endoscopes.

METHODS

In two single-use (LithoVue™, Boston Scientific; Pusen Uscope UE3011™), and one reusable ureterorenoscope (Flex-Xc™, Karl Storz), we investigated flow rates, deflection, illuminance, and intrapelvic pressure in a porcine kidney model. Subjective image quality was assessed using a standardized questionnaire. Common insertable devices were applied to investigate additional influence on physical properties.

RESULTS

Significant variability in maximum flow rates was observed (Flex-Xc™: 25.8 ml/min, LithoVue™: 30.3 ml/min, Pusen™: 33.4 ml/min, p < 0.05). Insertion of a guide wire resulted in the highest reduction of flow rates in all endoscopes. Flection led to a reduction of absolute flow rates up to 9.4% (Flex-Xc™). Light intensity at 20/50 mm distance was 9090 lx/1857 lx (Flex-Xc™) and 5733 lx/1032 lx (LithoVue™) and 2160 lx/428 lx (Pusen™), respectively (p < 0.05). Subjective image quality score was highest using the Flex-Xc™ endoscope. During manipulation, maximum intrarenal pressure up to 66 mmHg (Pusen™) was measured.

CONCLUSIONS

Significant differences in physical and optical properties of single-use or reusable flexible ureterorenoscopes are present, with putative influence on surgical efficacy and complications. Further comparative evaluation of single-use and reusable endoscopes in a clinical scenario is useful. Moreover, utilization of ureteral access sheaths may be considered to avoid renal damage.

First clinical evaluation of the new single-use flexible and semirigid Pusen ureteroscopes

Introduction

The purpose of the present study was to clinically evaluate two new single-use Pusen ureteroscopes, one semirigid with a flexible tip (srURS) and one flexible (fURS).

Materials and methods

During ten consecutive procedures (five srURS and five fURS), we subjectively evaluated on a scale from 0 (poor) to 10 (excellent), the scope's deflection, image quality, and maneuverability prior to, during and after the surgery. Patient demographics, complications with the devices, and troubleshooting were recorded.

Results

There were a total of ten patients, five of which were female while the other five were male. Mean age was 58.9 years. Seven patients had a single kidney stone with mean size of 9.6 mm (1.6-20 mm). Half of the patients were pre-stented. For the fURS, the preoperative image quality rating was 8.4 (8-10), compared with 6.8 (4-9) during surgery. The preoperative deflection rating was 9.6+ 0.9 (8-10), while during surgery this decreased to 8.0 (6-10) and to 6.0 (4-8) when using a laser fiber. The srURS had a preoperative image quality rating of 9.2 (8-10), which decreased to 7.6 (6-9) while using the scope. The deflection rating decreased from 9.4 (7-10) preoperatively to 7.0 (1-10) postoperatively, and a similar reduction was observed in the maneuverability rating, from 9.6 (8-10) to 7.4 (1-10). Ureteroscopy was considered as a standard in four of the fURS and three of the srURS procedures. The mean overall satisfaction rating was 6.

Conclusions

The two new single-use ureteroscopes, one flexible and one semirigid, were considered to have allowed standard ureteroscopy in four and three out of the five procedures for each scope, respectively. The image quality, deflection, and maneuverability ratings decreased during the procedure for both scopes.