Totally tubeless, tubeless, and tubed percutaneous nephrolithotomy for treating kidney stones

BACKGROUND

Percutaneous nephrolithotomy (PNL) is the standard of care for removing large kidney stones (> 2 cm). Once the procedure is complete, different exiting strategies exist to manage the percutaneous tract opening, including placement of an external nephrostomy tube, placement of an internal ureteral stent, or no external or internal tube. The decision to place or not place a tube is handled differently among clinicians and may affect patient outcomes.

OBJECTIVES

To assess the effects of tubeless PNL (with ureteral stenting), totally tubeless PNL (without ureteral stenting or nephrostomy), and standard PNL (nephrostomy only) for the treatment of kidney stones in adults.

SEARCH METHODS

We performed a systematic literature search in multiple biomedical databases (CENTRAL, MEDLINE, Embase, Web of Science), as well as in two clinical trial registries. We also handsearched reference lists of relevant publications and conference proceedings. We applied no language restrictions. The latest search update was conducted in September 2022.

SELECTION CRITERIA

We included randomized controlled and quasi-randomized controlled trials of adult patients who received tubeless, totally tubeless, or standard PNL for treating kidney stones. We defined tubeless PNL as no nephrostomy tube, but ureteral stenting, while totally tubeless PNL meant no nephrostomy tube or ureteral stenting. Both interventions were compared to standard PNL with placement of a nephrostomy tube (only). We considered access tubes of any sizes. We only considered unilateral PNL with single-tract access. There were no exclusions on stone composition, size, or location.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the literature, extracted data, assessed risk of bias, and rated the certainty of evidence using GRADE. Primary outcomes were severe adverse events and postoperative pain, and secondary outcomes were operating time, length of hospital stay, and stone-free rate. We used the random-effects model for meta-analysis.

MAIN RESULTS

We included 10 studies in the review. Participant age varied among studies, ranging from 20 to 60 years. Detailed information on stone characteristics was rarely presented. Tubeless PNL versus standard PNL We are very uncertain whether there is a difference in severe adverse events (SAEs) between tubeless PNL and standard PNL (risk ratio (RR) 1.53, 95% confidence interval (CI) 0.14 to 16.46; I2 = 42%; 2 studies, 46 participants; very low-certainty evidence). Tubeless PNL may have little to no effect on pain on postoperative day one (mean difference (MD) 0.56 lower, 95% CI 1.34 lower to 0.21 higher; I2 = 84%; 4 studies, 186 participants; low-certainty evidence), and probably results in little to no difference in operating room time (MD 0.40 longer (in minutes), 95% CI 4.82 shorter to 5.62 longer; I2 = 0%; 3 studies, 81 participants; moderate-certainty evidence). Tubeless PNL may reduce length of hospital stay (MD 0.90 shorter, 95% CI 1.45 shorter to 0.35 shorter; I2 = 84%; 6 studies, 238 participants; low-certainty evidence). We are very uncertain of the effect of tubeless PNL on blood transfusions (RR 0.64, 95% CI 0.16 to 2.52; I2 = 0%; 4 studies, 161 participants; very low-certainty evidence), sepsis or fever (RR 0.50, 95% CI 0.05 to 4.75; I2 = not applicable; 2 studies, 82 participants; very low-certainty evidence), or readmissions (RR 1.00, 95% CI 0.07 to 14.21; I2 = not applicable, 1 study, 24 participants; very low-certainty evidence). Totally tubeless versus standard PNL Totally tubeless PNL may result in lower SAE rates (RR 0.49, 95% CI 0.19 to 1.25; I2 = 0%; 2 studies, 174 participants; low-certainty evidence) and pain on postoperative day one (MD 3.60 lower, 95% CI 4.24 lower to 2.96 lower; I2 = Not applicable; 1 study, 50 participants; low-certainty evidence). Totally tubeless PNL may result in little to no difference in operating room time (MD 6.23 shorter (in minutes), 95% CI 14.29 shorter to 1.84 longer; I2 = 72%; 2 studies, 174 participants; moderate-certainty evidence) and sepsis or fever (RR 0.33, 95% CI 0.01 to 7.97; I2 = not applicable; 1 study, 90 participants; low-certainty evidence). Totally tubeless PNL likely shortens the length of hospital stay (MD 1.55 shorter, 95% CI 1.82 shorter to 1.29 shorter; I2 = 0%; 4 studies, 274 participants; moderate-certainty evidence). We are very uncertain of the effect of totally tubeless PNL on blood transfusions (RR 0.62, 95% CI 0.26 to 1.48; I2 = 0%; 4 studies, 274 participants; very low-certainty evidence) or readmissions (RR not estimable, 95% CI not estimable; I2 = not applicable; 1 study, 50 participants; very low-certainty evidence). We found no studies comparing tubeless mini versus standard mini-PNL or totally tubeless mini versus standard mini-PNL.

AUTHORS' CONCLUSIONS

When comparing tubeless to standard PNL with regard to the predefined primary outcomes of this review, there may be little difference in early postoperative pain, while we are very uncertain of the effect on SAEs. People treated with tubeless PNL may benefit from a reduced length of stay compared to standard PNL. When comparing totally tubeless to standard PNL, early postoperative pain and severe adverse events may be reduced with totally tubeless PNL. The certainty of evidence by outcome was mostly very low (range: moderate to very low) for the comparison of tubeless to standard PNL and low (range: moderate to very low) for the comparison of totally tubeless to standard PNL. The most common reasons for downgrading the certainty of the evidence were study limitations, inconsistency, and imprecision. We did not find randomized trial evidence for other comparisons. Overall, further and higher-quality studies are needed to inform clinical practice.

In vivo Temperature Assessment during Holmium Laser Enucleation of the Prostate

INTRODUCTION

Holmium laser enucleation of the prostate (HoLEP) has become popular worldwide for the surgical treatment of benign prostate hyperplasia. Holmium laser is considered an ideal transurethral thermomechanical device for enucleating the prostate. Although there is evidence on Ho:YAG laser-related heat generation, the studies mainly investigated ex vivo temperature generation during holmium laser lithotripsy. In this in vivo study, we aimed to assess for the first time the real-time heat generated during HoLEP.

METHODS

Fifteen HoLEP procedures were included. The study was conducted over a time period of 16 months. To investigate the temperature generation, a preoperatively inserted rectal temperature probe and a temperature sensor within a suprapubic bladder catheter were used to record the temperature change during enucleation and coagulation.

RESULTS

The mean values of the temperature change during the laser enucleation and coagulation were -0.35 ± 0.203 K (IQR: 0.23) and +0.14 ± 0.259 K (IQR: 0.3), respectively, in rectal measurements. Temperature differences during laser use and coagulation were <+1 K and <+5 K, respectively, in bladder measurements. We measured no temperature >37.1°C during the procedures and no temperature values considered harmful to the human body.

CONCLUSION

Sufficient irrigation flow rates and irrigation monitoring during HoLEP are obligatory. To prevent a high and uncontrolled temperature rise, the surgeon or operating room staff should pay attention to the irrigation's continuity.

Temperature assessment study of ex vivo holmium laser enucleation of the prostate model

Purpose

There isscarce evidence to date on how temperature develops during holmium laser enucleation of the prostate (HoLEP). We aimed to determine the potential heat generation during HoLEP under ex vivo conditions.

Methods

We developed two experimental setups. Firstly, we simulated HoLEP ex vivo using narrow-neck laboratory bottles mimicking enucleation cavities and a prostate resection trainer. Seven temperature probes were placed at different locations in the experimental setup, and the heat generation was measured separately during laser application. Secondly, we simulated high-frequency current-based coagulation of the vessels using a roller probe.

Results

We observed that the larger the enucleated cavity, the higher the temperature rises, regardless of the irrigation flow rate. The highest temperature difference with an irrigation flow was approximately + 4.5 K for a cavity measuring 100ccm and a 300 ml/min irrigation flow rate. The higher flow rate generates faster removal of the generated heat, thus cooling down the artificial cavity. Furthermore, the temperature differences at different irrigation flow rates (except at 0 ml/min) were consistently below 5 K. Within the resection trainer, the temperature increase with and without irrigation flow was approximately 0.5 K and 3.0 K, respectively. The mean depth of necrosis (1084 ± 176 µm) achieved by the roller probe was significantly greater when using 144 W energy.

Conclusion

Carefully adjusted irrigation and monitoring during HoLEP are crucial when evacuating the thermal energy generated during the procedure. We believe this study of ours provides evidence with the potential to facilitate clinical studies on patient safety.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-022-04041-z.

Thermal effects of thulium: YAG laser treatment of the prostate-an in vitro study

PURPOSE

To objectively determine whether there is potential thermal tissue damage during Tm:YAG laser-based LUTS treatment.

METHODS

Our experimental model was comprised of a prostatic resection trainer placed in a 37 °C water bath. In a hollowed-out central area simulating the urethral lumen, we placed a RigiFib 800 fibre, irrigation inflow regulated with a digital pump, and a type K thermocouple. A second thermocouple was inserted 0.5/1 cm adjacently and protected with an aluminum barrier to prevent it from urethral fluid. We investigated continuous and intermittent 120 W and 80 W laser application with various irrigation rates in eight measurement sessions lasting up to 14 min. Thermal measurements were recorded continuously and in real-time using MatLab. All experiments were repeated five times to balance out variations.

RESULTS

Continuous laser application at 120 W and 125 ml/min caused a urethral ∆T of ~ 15 K and a parenchymal temperature increase of up to 7 K. With 50 ml/min irrigation, a urethral and parenchymal ∆T of 30 K and 15 K were reached, respectively. Subsequently and in absence of laser application, prostatic parenchyma needed over 16 min to reach baseline body temperature. At 80 W lower temperature increases were reached compared to similar irrigation but higher power.

CONCLUSIONS

We showed that potentially harming temperatures can be reached, especially during high laser power and low irrigation. The heat generation can also be conveyed to the prostate parenchyma and deeper structures, potentially affecting the neurovascular bundles. Further clinical studies with intracorporal temperature measurement are necessary to further investigate this potentially harming surgical adverse effect.

Soft Urinary Bladder Phantom for Endoscopic Training

Bladder cancer (BC) is the main disease in the urinary tract with a high recurrence rate and it is diagnosed by cystoscopy (CY). To train the CY procedures, a realistic bladder phantom with correct anatomy and physiological properties is highly required. Here, we report a soft bladder phantom (FlexBlad) that mimics many important features of a human bladder. Under filling, it shows a large volume expansion of more than 300% with a tunable compliance in the range of 12.2 ± 2.8 - 32.7 ± 5.4 mL cmH2O-1 by engineering the thickness of the bladder wall. By 3D printing and multi-step molding, detailed anatomical structures are represented on the inner bladder wall, including sub-millimeter blood vessels and reconfigurable bladder tumors. Endoscopic inspection and tumor biopsy were successfully performed. A multi-center study was carried out, where two groups of urologists with different experience levels executed consecutive CYs in the phantom and filled in questionnaires. The learning curves reveal that the FlexBlad has a positive effect in the endourological training across different skill levels. The statistical results validate the usability of the phantom as a valuable educational tool, and the dynamic feature expands its use as a versatile endoscopic training platform.

Management and endovascular therapy of ureteroarterial fistulas: experience from a single center and review of the literature

Background

Ureteroarterial fistula (UAF) is a rare but potentially life threatening disease. The aim of this study was to evaluate the outcome of endovascular therapy for UAF treatment.

Methods

This retrospective case series evaluates a single center experience of percutaneous stent graft (SG) angioplasty and/or coil embolization for UAF. Patient follow-up included technical and early clinical success, complications and revisional procedures. We also conducted a systematic review of the literature reporting on endovascular UAF management.

Results

We identified 17 UAF in 16 patients (12 male, 4 female, mean age 69.8 ± 11.3 years) who underwent endovascular UAF therapy at our tertiary hospital. All patients presented with hematuria. 5/17 (29.4%) presented with flank pain, in 7 (41.2%) cases patients were in hypovolemic shock. Risk factors of UAF included chronic indwelling ureteral stents in all fistulas, major pelvic surgery in 13 cases (76.5%). In 6 cases (35.3%) SG were placed from the common iliac artery (CIA) to the external iliac artery (EIA) following coil embolization of the proximal internal iliac artery (IIA). SG placement without previous coil embolization was performed in 10 fistulas (58.8%). In one case only coil embolization of the IIA was performed. Mean follow-up was 654 (range: 1–3269) days. All procedures were technically successful and no procedure related deaths occurred during follow-up. During the initial hospital stay hematuria disappeared in 14/17 cases (82.4%). Overall, four patients suffered recurrent hematuria, which in three cases resolved after a secondary intervention. One recurrent UAF related death occurred during follow-up 229 days after initial treatment.

A total of 152 UAF cases were additionally analyzed from our systematic literature review: SG placement with or without embolization was performed in 140 cases (92.1%) while embolization alone was done in 12 cases (7.9%). Complications included UAF recurrence (18/152, 11.8%), SG thrombosis (7/140, 5%), and SG infections (5/140, 3.6%) with an overall complications rate of 13.8%. Five patients died due to UAF (3.3%).

Conclusion

Endovascular therapy offers high technical success rates and rapid bleeding control of UAF. Severe complications like SG occlusions or SG infections are rare but significant. Antibiotic treatment and single anti-platelet therapy improve SG durability as well as close and long follow-up to timely perform repeated endovascular or surgical treatment if necessary.

Evidence-based medicine

Level 4, case series.

Endourological Training Using 3D-Printed Bladder Phantoms: Development and Prospective Evaluation

Background: To create and evaluate a realistic, anatomically accurate, and user-friendly bladder phantom for reproducible endourological training purposes and endoscope mastery. Materials and Methods: The anatomy of full bladders was mapped from human computed tomography datasets. After a 3D model development process, content evidence and response process evidence (RPE) of the phantom were evaluated using the system usability scale (SUS), 5-point Likert scale questionnaires, and task execution of experienced urologists (U) and endoscopy-naive medical students (MS) in two training sessions (first vs second). Required validation cohort sizes (1:10) of the evaluating urologists (n = 12) and students (n = 115) were precalculated. Time measurements were recorded. Students were additionally evaluated by a validated global psychomotor assessment score (GPSS). Group comparisons were calculated by the Mann-Whitney U test. All tests were two sided with p < 0.05 considered statistically significant. Results: Content evidence was assessed by urologists with an "excellent" SUS score of 89.4 ± 5.9 and an average "agreement" of ≥4 pts in the Likert scale questionnaires. RPE was assessed by intra- and intergroup time comparison for the execution of endoscopic tasks (cystoscopy [CY], guidewire insertion, and tumor biopsy). For CY, U: first 17.6 ± 4.4 seconds vs second 12.4 ± 2.0 seconds, p = 0.002; MS: first 56.6 ± 28.2 seconds vs second 28.6 ± 14.7 seconds, p < 0.001; U vs MS: first U 17.6 ± 4.4 seconds vs first MS 56.6 ± 28.2 seconds, p < 0.001, second U 12.4 ± 2.0 seconds vs second MS 28.6 ± 14.7 seconds, p < 0.001. Significant time differences were documented for all tasks and sessions (p < 0.001). Additionally, significant GPSS differences were recorded between the sessions (GPSS: first 20.4 ± 5.1 pts vs second 24.7 ± 4.0 pts, p < 0.001). Conclusions: Our low-fidelity 3D-printed bladder, called BladCap, is an easy-to-assemble, inexpensive, and robust phantom. We present data, which establish construct validity to support use as a clinical training device.

Feasibility of an Updated Randomised Controlled Trial on Surgical Urolithiasis Treatments: The Pilot Trial for the German Endoscopic versus Shock Wave Therapy Study (GESS)

Data comparing treatments for urolithiasis are often outdated, with inconsistent results or poor methodological and reporting quality. We report a pilot study in preparation for a larger multicentre randomised controlled trial (RCT) comparing shockwave therapy and ureteroscopy in patients with a single urinary stone of ≤20 mm in the upper urinary tract. Primary objectives included screening completeness, patients' willingness to participate, their remaining in the study, the suitability of the eligibility criteria, and the acceptability of the outcome measures. Screened individuals not invited to participate were those with no indication for active treatment among referred patients (n = 166), those who staff failed to screen (n = 99), and patients not meeting the inclusion criterion of a single stone (n = 422). Of the 176 patients invited, 116 refused to participate. Ultimately, we were able to recruit 60 patients within 34 mo. All patients underwent their allocated treatments. This pilot trial provides an in-depth analysis of the feasibility of an RCT on surgical treatments for upper urinary tract urolithiasis in a highly regulated health care system. The study procedures and outcome measures proved acceptable and feasible. On the basis of these data, we propose a pragmatic, multicentre RCT to deliver updated, high-level evidence on the efficacy of currently available treatments for urolithiasis. PATIENT SUMMARY: We performed a small pilot trial comparing current treatments in urolithiasis. We were able to prove the feasibility of a larger multi-institutional trial with regard to the time needed to recruit an adequate number of patients and the acceptability of the treatments and outcome measures.

Mixed reality for teaching catheter placement to medical students: a randomized single-blinded, prospective trial

BACKGROUND

Cost-effective methods to facilitate practical medical education are in high demand and the "mixed-reality" (MR) technology seems suitable to provide students with instructions when learning a new practical task. To evaluate a step-by-step mixed reality (MR) guidance system for instructing a practical medical procedure, we conducted a randomized, single-blinded prospective trial on medical students learning bladder catheter placement.

METHODS

We enrolled 164 medical students. Students were randomized into 2 groups and received instructions on how to perform bladder catheter placement on a male catheterization training model. One group (107 students) were given their instructions by an instructor, while the other group (57 students) were instructed via an MR guidance system using a Microsoft HoloLens. Both groups did hands on training. A standardized questionnaire covering previous knowledge, interest in modern technologies and a self-evaluation was filled out. In addition, students were asked to evaluate the system's usability. We assessed both groups's learning outcome via a standardized OSCE (objective structured clinical examination).

RESULTS

Our evaluation of the learning outcome revealed an average point value of 19.96 ± 2,42 for the control group and 21.49 ± 2.27 for the MR group - the MR group's result was significantly better (p = 0.00). The self-evaluations revealed no difference between groups, however, the control group gave higher ratings when evaluating the quality of instructions. The MR system's assessment showed less usability, with a cumulative SUS (system usability scale) score of 56.6 (lower half) as well as a cumulative score of 24.2 ± 7.3 (n = 52) out of 100 in the NASA task load index.

CONCLUSIONS

MR is a promising tool for instructing practical skills, and has the potential to enable superior learning outcomes. Advances in MR technology are necessary to improve the usability of current systems.

TRIAL REGISTRATION

German Clinical Trial Register ID: DRKS00013186.

Therapy-Refractory Matrix Staghorn in a Kidney Transplant Recipient: Endoscopic Percutaneous Morcellation as a Novel Treatment Option

Background: Urolithiasis of transplant kidneys usually encompasses a challenging clinical situation due to specific anatomical conditions and the patients' immunological status. In this case report, we describe the treatment of a rare Proteus mirabilis matrix staghorn stone applying percutaneous nephrolithotomy in combination with matrix stone extraction by morcellation while utilizing endo-urological equipment designed for transurethral prostate surgery. Case Presentation: We present the case of a 44-year-old Caucasian woman who had undergone a post-mortal kidney transplant at age 37. After recurrent urinary tract infections, symptomatic obstructions of the transplant ureter, and multiple surgical interventions (73 Double-J stent and nephrostomy placements and three ureter re-implantations), permanent percutaneous nephrostomy drainage was established 6 years after her kidney transplantation. The patient was referred to our department due to recurrent dysfunction of the nephrostomy tube caused by blockage due to stone-matrix material and a staghorn calculus in the transplant kidney's collecting system. Microbiological examination of the stone material retrieved from the nephrostomy tube revealed massive P. mirabilis contamination. In this work, we present a novel percutaneous technique of matrix stone removal by relying on endoscopic equipment usually employed during prostate surgery by urologists. Conclusion: Percutaneous matrix stone morcellation is a technically challenging but feasible method that might be considered as a salvage treatment strategy in situations described earlier and in highly selective cases. However, for this extremely rare stone entity and individual clinical presentations, matrix stone morcellation seems to be a reasonable alternative before considering more radical interventions such as open nephrolithotomy. Selection criteria are a very soft stone, large-caliber percutaneous access to the collecting system, and enough space in the collecting system to execute morcellation.

Application of artificial neural networks for automated analysis of cystoscopic images: a review of the current status and future prospects

BACKGROUND

Optimal detection and surveillance of bladder cancer (BCa) rely primarily on the cystoscopic visualization of bladder lesions. AI-assisted cystoscopy may improve image recognition and accelerate data acquisition.

OBJECTIVE

To provide a comprehensive review of machine learning (ML), deep learning (DL) and convolutional neural network (CNN) applications in cystoscopic image recognition.

EVIDENCE ACQUISITION

A detailed search of original articles was performed using the PubMed-MEDLINE database to identify recent English literature relevant to ML, DL and CNN applications in cystoscopic image recognition.

EVIDENCE SYNTHESIS

In total, two articles and one conference abstract were identified addressing the application of AI methods in cystoscopic image recognition. These investigations showed accuracies exceeding 90% for tumor detection; however, future work is necessary to incorporate these methods into AI-aided cystoscopy and compared to other tumor visualization tools. Furthermore, we present results from the RaVeNNA-4pi consortium initiative which has extracted 4200 frames from 62 videos, analyzed them with the U-Net network and achieved an average dice score of 0.67. Improvements in its precision can be achieved by augmenting the video/frame database.

CONCLUSION

AI-aided cystoscopy has the potential to outperform urologists at recognizing and classifying bladder lesions. To ensure their real-life implementation, however, these algorithms require external validation to generalize their results across other data sets.

Current Disposable Ureteroscopes: Performance and Limitations in a Standardized Kidney Model

Objectives: Due to the increasing fragility of the instruments and rising concerns about the sterility of reprocessable scopes, several single-use devices for flexible ureteroscopy have been introduced. In this study, we compare currently available disposable digital and fiberoptic flexible ureteroscopes with a contemporary reusable fiberoptic device. Materials and Methods: LithoVue™, Pusen Uscope^® (UE3011, UE3022), Flexor^®Vue™, and a reusable fiber optic flexible ureteroscope (BOA vision^®) were tested in kidney models. The setup included (1) visualization of all calices (correct assignment of colored pearls) and (2) the extraction of human calculi with a standard disposable extraction device (NGage^®). We documented the effective visualization, stone extraction, and times to completion. In addition, the surgeons' workload and performance were determined using the National Aeronautics and Space Administration-Task Load Index. Results: In visualizing and identifying calices, the LithoVue and both generations of the Uscope performed similarly, but time to completion was significantly longer for all single-use devices in comparison with the Boa Vision. LithoVue retracted stones almost as well as the reusable scope (97% vs 95%/82%/96% stone clearance), while accessibility was impeded using Uscope UE3011, as reflected by the retrieval time per stone (73 vs 102 seconds/stone). This disadvantage has, however, been overcome with the new Uscope Generation UE3022, showing a retrieval time of only 65 seconds per stone, excelling over the reusable scope in this category. The Uscope UE3022 image quality was also rated best, but showed no significant difference. Conclusions: In comparison with disposable ureteroscopes available, LithoVue offers performance and characteristics similar to a reusable device, while the FlexorVu's performance does not yet yield satisfactory results for clinical use. The first generation of Uscope exhibits potential, but requires further technical improvements to match the performance of a reusable device. With the new-generation UE3022, Pusen has made significant improvement and offers a quality comparable with the LithoVue's.

Preclinical and Clinical Evaluation of a Novel, Variable-View, Rigid Endoscope for Female Cystoscopy

OBJECTIVE

To evaluate the preclinical and clinical performance of the pivoting lens rigid Endocameleon (ECAM) endoscope in white light cystoscopy (WLC).

MATERIALS AND METHODS

Preclinical evaluation was performed ex vivo in CT-based, anatomically accurate and validated bladder phantoms. Six defined tasks with objective endpoints were compared between ECAM-WLC and rigid WLC (30° view angle, rWLC) in 30 interventions. Subsequently, the comparison was transferred to in vivo n = 21 interventions. A validated usability score (System Usability Scale, SUS) as well as physician and patient-related outcomes were assessed using Likert-scale-based questionnaires. Intra- and postinterventional complications were recorded according to the Clavien-Dindo classification.

RESULTS

The ex vivo evaluation showed a significant superiority of ECAM-WLC in 4 of 6 endoscopic tasks. Noteworthy is the lower pressure on the bladder neck due to the endoscopesalteration of the endoscope (4/60 vs 17/60, P <.0001) and a more precise imaging of all bladder regions (22/30 vs 30/30, P = .046), including the anterior wall (0/30 vs 28/30, P <.0001). In vivo, surgeons rated the ECAM-WLC with an "excellent" SUS of 86.79%, also expressing that ECAM-WLC would enhance bladder surface visualization (4.52/5.0 ± 0.51), with a preferred use for ECAM-WLC during their next cystoscopy (4.62 ± 0.50). Patients reported ECAM-WLC to be less painful (4.5/5.0 ± 0.84) compared to rWLC. No intervention-related complications were observed.

CONCLUSION

ECAM-WLC is a safe and accessible procedure that could improve conventional diagnostic WLC by combination of the advantages of fWLC and rWLC.

Use of Artificial Intelligence for Medical Literature Search: Randomized Controlled Trial Using the Hackathon Format

Background

Mapping out the research landscape around a project is often time consuming and difficult.

Objective

This study evaluates a commercial artificial intelligence (AI) search engine (IRIS.AI) for its applicability in an automated literature search on a specific medical topic.

Methods

To evaluate the AI search engine in a standardized manner, the concept of a science hackathon was applied. Three groups of researchers were tasked with performing a literature search on a clearly defined scientific project. All participants had a high level of expertise for this specific field of research. Two groups were given access to the AI search engine IRIS.AI. All groups were given the same amount of time for their search and were instructed to document their results. Search results were summarized and ranked according to a predetermined scoring system.

Results

The final scoring awarded 49 and 39 points out of 60 to AI groups 1 and 2, respectively, and the control group received 46 points. A total of 20 scientific studies with high relevance were identified, and 5 highly relevant studies (“spot on”) were reported by each group.

Conclusions

AI technology is a promising approach to facilitate literature searches and the management of medical libraries. In this study, however, the application of AI technology lead to a more focused literature search without a significant improvement in the number of results.

Current Standards in the Endoscopic Management of Bladder Cancer: A Survey Evaluation among Urologists in German-Speaking Countries

INTRODUCTION

To assess the current diagnostic, treatment, and documentation strategies for bladder cancer (BC) in German-speaking countries.

MATERIALS AND METHODS

A 14-item web-based survey was distributed among members of the German, Austrian, and Swiss Associations of Urology, addressing physicians who perform cystoscopies and transurethral resection of bladder tumors (TURB).

RESULTS

The survey was responded to by 308 of 5,564 urologists with a mean age of 49.5 years (response rate: 5.5%). The majority of participants (57.3%) practice in an outpatient setting. White light cystoscopy only is used by 60.2%, with additional photodynamic diagnosis and narrow band imaging by 36.8 and 12.5%, respectively. Endoscopic findings are documented in written form by 93.5%, followed by image capture (33.7%) and a central data archive (20.8%). Inpatient hospital urologists document cystoscopic findings by freehand drawing (21.4 vs. 11.4%, p = 0.017), and with a fixed bladder scheme (31.3 vs. 7.4%, <0.05) significantly more frequently. Cystoscopic findings are mainly conveyed to other health professionals in written form (77.4%), and significantly more often by inpatient urologists (p < 0.05).

CONCLUSIONS

Significant differences exist in the approach to documenting and communicating cystoscopic BC findings. Accurate graphic documentation of lesions, visualization of the mucosa's totality, and meticulous consultation of previous surgical reports require improvements to reduce recurrence and progression rates.

Analysis of Interfacial Effects in All-Solid-State Batteries with Thiophosphate Solid Electrolytes

All-solid-state batteries (ASSBs) present a promising route toward safe and high-power battery systems in order to meet the future demands in the consumer and automotive market. Composite cathodes are one way to boost the energy density of ASSBs compared to thin-film configurations. In this manuscript, we investigate composites consisting of β-Li₃PS₄ (β-LPS) solid electrolyte and high-energy Li(Ni_0.6Mn_0.2Co_0.2)O₂ (NMC622). The fabricated cells show a good cycle life with a satisfactory capacity retention. Still, the cathode utilization is below the values reported in the literature for systems with liquid electrolytes. The common understanding is that interface processes between the active material and solid electrolyte are responsible for the reduced performance. In order to throw some light on this topic, we perform 3D microstructure-resolved simulations on virtual samples obtained via X-ray tomography. Through this approach, we are able to correlate the composite microstructure with electrode performance and impedance. We identify the low electronic conductivity in the fully lithiated NMC622 as material inherent restriction preventing high cathode utilization. Moreover, we find that geometrical properties and morphological changes of the microstructure interact with the internal and external interfaces, significantly affecting the capacity retention at higher currents.

Current and future applications of machine and deep learning in urology: a review of the literature on urolithiasis, renal cell carcinoma, and bladder and prostate cancer

PURPOSE

The purpose of the study was to provide a comprehensive review of recent machine learning (ML) and deep learning (DL) applications in urological practice. Numerous studies have reported their use in the medical care of various urological disorders; however, no critical analysis has been made to date.

METHODS

A detailed search of original articles was performed using the PubMed MEDLINE database to identify recent English literature relevant to ML and DL applications in the fields of urolithiasis, renal cell carcinoma (RCC), bladder cancer (BCa), and prostate cancer (PCa).

RESULTS

In total, 43 articles were included addressing these four subfields. The most common ML and DL application in urolithiasis is in the prediction of endourologic surgical outcomes. The main area of research involving ML and DL in RCC concerns the differentiation between benign and malignant small renal masses, Fuhrman nuclear grade prediction, and gene expression-based molecular signatures. BCa studies employ radiomics and texture feature analysis for the distinction between low- and high-grade tumors, address accurate image-based cytology, and use algorithms to predict treatment response, tumor recurrence, and patient survival. PCa studies aim at developing algorithms for Gleason score prediction, MRI computer-aided diagnosis, and surgical outcomes and biochemical recurrence prediction. Studies consistently found the superiority of these methods over traditional statistical methods.

CONCLUSIONS

The continuous incorporation of clinical data, further ML and DL algorithm retraining, and generalizability of models will augment the prediction accuracy and enhance individualized medicine.

Stone-Free Rate after Treating Kidney Stones Exceeding 10 mm via Flexible Ureteroscopy: Can Endoscopic Assessment Replace Low-Dose Computed Tomography Control?

INTRODUCTION

It is unclear whether endoscopic assessment of the stone-free rate after flexible ureteroscopy (fURS) is as effective as assessment with low-dose computed tomography (CT) scan.

METHODS

Prospective documentation of patients with kidney stones > 10 mm diameter from 2 different centers (Freiburg, Regensburg), who underwent fURS and were declared to be endoscopically completely stone-free. Low-dose CT control performed 4-8 weeks postoperatively.

RESULTS/CONCLUSION

Thirty-eight patients were treated between October 2015 and August 2016 (12 F, 26 M). Average age was 55.9 years (range 19-82, SD 17.24), and body mass index was 29.7 kg/m2 (range 23.5-42.5, SD 4.37). There were 2.0 (range 1-7, SD 1.55) stones with a mean diameter of 15 mm (range 10-40, SD 6.78) per kidney. Mean surgery time was 74 min (range 38-124, SD 24.28), and lithotripsy was necessary in 33 cases. CT was performed 5.4 weeks afterwards (range 4-8, SD 1.43). One patient had a 2 mm residual which was extracted by URS. Strictly speaking, endoluminal stone removal control failed in only that patient, yielding a negative predictive value of 97%. A routine postoperative CT scan would thus appear unnecessary in the case of negative endoscopic control for residual fragments and should be avoided to reduce radiation exposure. Further investigations with larger patient populations are necessary.

[Current trends in flexible ureteroscopy: an update]

Flexible ureteroscopy (fURS) has become a success story in urology. Since its implementation into the treatment of urolithiasis, fURS has demonstrated excellent clinical performance and safety. In recent years, the spread of disposable ureteroscopes has shaped the field of endoscopic stone treatment. However, the primary advantage of these devices is that they improve the workflow in urology theatres (no sterilisation, no repair costs) and possibly minimise bacteria transfer in working channels rather than being a real technological "game changer". Novel disruptive improvements such as automatic laser lithotripsy or intrarenal pressure and temperature control in real time are still waiting to enter the clinical routine. These innovations might take fURS to the next level and disruptively change endoscopic stone treatment.

Micro-fluorescence lifetime and spectral imaging of ytterbium doped laser materials

We present the application of a confocal fluorescence microscope to the analysis of Yb-doped solid-state laser materials, with examples of Yb-doped crystals, photonic crystal fibers and fiber preforms made with different manufacturing processes. Beside the fluorescence lifetime image itself, a microscopic spectral fluorescence emission analysis is presented and spatially resolved emission cross sections are obtained. Doping concentration and its distributions and other laser optical parameters are measured, which help to analyze manufacturing steps. Further properties like photodarkening and saturation are addressed.

Image-based 3D surface approximation of the bladder using structure-from-motion for enhanced cystoscopy based on phantom data

Bladder cancer is likely to recur after resection. For this reason, bladder cancer survivors often undergo follow-up cystoscopy for years after treatment to look for bladder cancer recurrence. 3D modeling of the bladder could provide more reliable cystoscopic documentation by giving an overall picture of the organ and tumor positions. However, 3D reconstruction of the urinary bladder based on endoscopic images is challenging. This is due to the small field of view of the endoscope, considerable image distortion, and occlusion by urea, blood or particles. In this paper, we will demonstrate a method for the conversion of uncalibrated, monocular, endoscopic videos of the bladder into a 3D model using structure-from-motion (SfM). First of all, frames are extracted from video sequences. Distortions are then corrected in a calibration procedure. Finally, the 3D reconstruction algorithm generates a sparse surface approximation of the bladder lining based on the corrected frames. This method was tested using an endoscopic video of a phantom that mimics the rich structure of the bladder. The reconstructed 3D model covered a large part of the object, with an average reprojection error of 1.15 pixels and a relative accuracy of 99.4%.

Thermal effects of Ho: YAG laser lithotripsy: real-time evaluation in an in vitro model

PURPOSE

To evaluate the thermal effect of Ho:YAG laser lithotripsy in a standardized in vitro model via real-time temperature measurement.

METHODS

Our model comprised a 20 ml test tube simulating the renal pelvis that was immersed in a 37 °C water bath. Two different laser fibers [FlexiFib (15-45 W), RigiFib 1000 (45-100 W), LISA laser products OHG, Katlenburg-Lindau, Germany] were placed in the test tube. An Ho:YAG 100 W laser was used in all experiments (LISA). Each experiment involved 120 s of continuous laser application, and was repeated five times. Different laser settings (high vs. low frequency, high vs. low energy, and long vs. short pulse duration), irrigation rates (0 up to 100 ml/min, realized by several pumps), and human calcium oxalate stone samples were analyzed. Temperature data were acquired by a real-time data logger with thermocouples (PICO Technology, Cambridgeshire, UK). Real-time measurements were assessed using MatLab^®.

RESULTS

Laser application with no irrigation results in a rapid increase in temperature up to ∆28 K, rising to 68 °C at 100 W. Low irrigation rates yield significantly higher temperature outcomes. Higher irrigation rates result immediately in a lower temperature rise. High irrigation rates of 100 ml/min result in a temperature rise of 5 K at the highest laser power setting (100 W).

CONCLUSIONS

Ho:YAG laser lithotripsy might be safe provided that there is sufficient irrigation. However, high power and low irrigation resulted in potentially tissue-damaging temperatures. Laser devices should, therefore, always be applied in conjunction with continuous, closely monitored irrigation whenever performing Ho:YAG laser lithotripsy.

Viability and biocompatibility of an adhesive system for intrarenal embedding and endoscopic removal of small residual fragments in minimally-invasive stone treatment in an in vivo pig model

PURPOSE

To evaluate the viability and biocompatibility of a novel, patented bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy. Complete stone clearance via active removal of residual fragments (RF) after intracorporeal laser lithotripsy may be time-consuming and fail in many cases. Therefore, the novel adhesive has been developed and evaluated for the first time in an in vivo pig model in the present work.

METHODS

Four female domestic pigs underwent flexible ureteroscopy (RIRS) or percutaneous nephrolithotomy (PNL) under general anesthesia (8 kidneys, 4 × RIRS, 4 × PNL) evaluating the bioadhesive system.

INTERVENTIONS

RIRS without adhesive system (sham procedure, kidney I); 3 × RIRS using the bioadhesive system (kidneys II-IV); and 4 × PNL using the bioadhesive system (V-VIII). We endoscopically inserted standardized human stone probes followed by comminution using Ho:YAG lithotripsy. The bioadhesive (kidney II-VIII) was then applied and the adhesive-stone fragment complex extracted. After nephrectomy, all kidneys were evaluated by two independent, blinded pathologists. Endpoints were the procedure's safety and adhesive system's biocompatibility.

RESULTS

We observed no substantial toxic effects. We were able to embed and remove 80-90% of fragments. However, because of the pig's hampering pyelocaliceal anatomy, a quantified, proportional assessment of the embedded fragments was compromised.

CONCLUSIONS

For the first time, we demonstrated the proven feasibility and safety of this novel bioadhesive system for embedding and endoscopically removing small RF in conjunction with a lack of organ toxicity in vivo.

The stone surgeon in the mirror: how are German-speaking urologists treating large renal stones today?

OBJECTIVE

To elucidate the current treatment strategies of LRS in German-speaking Europe. Little is known about the treatment of large renal stones (LRS > 3 cm) in daily urological practice. LRS therapy can be, however, challenging and hazardous.

MATERIALS AND METHODS

A 39 item web-based survey was performed among urologists listed by the German, Austrian and Swiss Associations of Urology, addressing professionals treating LRS "on their own" and working in a German-speaking country. Uniparametric descriptions indicated as absolute numbers and percentages without p values, simple linear associations and bubble plots without arithmetic means or bar charts with standard deviation between targeted parameters and percentages were used.

RESULTS

266 of the 6586 responding urologists claimed to treat urinary stones on a regular basis. The majority of them were male (90.2%) and over 50 years old (42.9%). Most stones are treated in non-university hospitals (69.5%). 81.9% of all the institutions treat more than 150 cases/y. Open surgery is still performed in 45.5% of the centres, laparoscopy in 32%. Percutaneous nephrolithotomy (PNL) is the primary treatment option. Antimicrobial strategies vary considerably. Serious complications seem to be rare. However, quite a few responders reported treatment-related deaths. The main limitation is the absolute number of urologists performing LRS treatment, which is unknown.

CONCLUSIONS

The German-speaking urologist treating LRS is a male and over 50. Although he performs PNL primarily, he is not averse to open surgery and SWL. He applies guidelines and employs modern equipment. Only antimicrobial strategies are out of line with the international standards.

Robotic stone surgery - Current state and future prospects: A systematic review

Objective

To provide a comprehensive review of robot-assisted surgery in urolithiasis and to consider the future prospects of robotic approaches in stone surgery.

Materials and methods

We performed a systematic PubMed© literature search using predefined Medical Subject Headings search terms to identify PubMed-listed clinical research studies on robotic stone surgery. All authors screened the results for eligibility and two independent reviewers performed the data extraction.

Results

The most common approach in robotic stone surgery is a robot-assisted pyelolithotomy using the da Vinci™ system (Intuitive Surgical Inc., Sunnyvale, CA, USA). Several studies show this technique to be comparable to classic laparoscopic and open surgical interventions. One study that focused on ureteric stones showed a similar result. In recent years, promising data on robotic intrarenal surgery have been reported (Roboflex Avicenna™; Elmed Medical Systems, Ankara, Turkey). Initial studies have shown its feasibility and high stone-free rates and prove that this novel endoscopic approach is safe for the patient and comfortable for the surgeon.

Conclusions

The benefits of robotic devices in stone surgery in existing endourological, laparoscopic, and open treatment strategies still need elucidation. Although recent data are promising, more prospective randomised controlled studies are necessary to clarify the impact of this technique on patient safety and stone-free rates.

Is Endoscopic Vasectomy Just a Dream: An ex vivo Study on Feasibility and Reliability of Endoluminal Occlusion of Porcine Vas Deferens

INTRODUCTION AND AIM

Surgical vasectomy remains the gold standard for fertility control in men. Endoluminal occlusion of the seminal ducts, thus avoiding an external incision, may become an appealing alternative to this approach. As our group has shown, nontraumatic endoscopic inspection of the seminal ducts is feasible in the human cadaver. We investigated the feasibility and reliability of occlusion using several commercially available medical sealing agents in the porcine vas deferens (VD).

METHODS AND MAIN OUTCOME MEASURES

Tests were conducted using 25 porcine spermatic ducts (10 cm length) ex vivo. The explanted specimens were fixed and cannulated using the Seldinger technique. We administered 5 different agents (n-butyle-2-cyanoacrylate, n-butyle-2-cyanoacrylate in combination with a platinum vascular coil, Tissucol Duo S®, Gelita Spon® and AFP Plug®) endoluminally. Tightness was evaluated after 5, 15, 60, 360, 720, and 1,440 min for each of the five grades, respectively, using a solution of methylene blue and saline injected under controlled pressure of 300 mm Hg followed by histological examination.

RESULTS

All agents were administered into the porcine seminal ducts (4 out of 5 via a ureteric catheter). Gelita Spon® and Tissucol Duo S® did not occlude the lumen sufficiently, whereas n-butyle-2-cyanoacrylate, n-butyle-2-cyanoacrylate in combination with coil, Tissucol Duo and AFP Plug® performed satisfactorily. In particular, cyanoacrylate combined with a coil was able to close the seminal duct tightly and for a long time. Histological findings confirmed this sealant's gapless adhesion. AFP Plug® application revealed similarly good results. However, its form needs to be optimized to ensure its suitability for endoscopic use.

CONCLUSION

Various developments regarding minimally invasive fertility control methods have been underway for decades. Further miniaturization of endoscopy and novel materials may pave the way for endoscopic fertility control in males in the future. We demonstrated the potential of commercially available medical sealing agents to reliably occlude the porcine VD.

Single mode 4.3 kW output power from a diode-pumped Yb-doped fiber amplifier

We investigate the average power scaling of two diode-pumped Yb-doped fiber amplifiers emitting a diffraction-limited beam. The first fiber under investigation with a core diameter of 30 µm was able to amplify a 10 W narrow linewidth seed laser up to 2.8 kW average output power before the onset of transverse mode instabilities (TMI). A further power scaling was achieved using a second fiber with a smaller core size (23µm), which allowed for a narrow linewidth output power of 3.5 kW limited by stimulated Brillouin scattering (SBS). We mitigated SBS using a spectral broadening mechanism, which allowed us to further increase the output power to 4.3 kW only limited by the available pump power. Up to this power level, a high slope efficiency of 90% with diffraction-limited beam quality and without any sign of TMI or stimulated Raman scattering for a spectral dynamic range of higher than -80 dB was obtained.

Ultralow Radiation Exposure During Flexible Ureteroscopy in Patients With Nephrolithiasis-How Far Can We Go?

OBJECTIVE

To evaluate the feasibility and clinical performance of a novel surgeon technique and protocol targeting ultralow fluoroscopy usage in retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

All RIRS procedures between 2009 and 2015 for 10- to 20-mm renal calculi performed by the same 2 experienced urologists were eligible. All procedures were performed using a highly standardized step-by-step RIRS technique. This technique was modified by the ultralow radiation exposure RIRS protocol; herein, as much as possible of the standardized steps were performed without radiation control targeting ultralow fluoroscopy usage. Primary end points were fluoroscopy time and dose area product. Secondary end points were stone-free rate (SFR) and intraoperative complications according to Satava classification. End points were evaluated using scatter plots and linear regression model.

RESULTS

Overall, 174 procedures were assessed. Over the study period, fluoroscopy time and dose area product could be reduced from 167.7 s/318.4 cGy/cm² in 2009 to 7.4 s/6.4 cGy/cm² in 2015 (P <.001). SFR (66.7% in 2009; 100% in 2015) and complications (Satava 1 and 2: 28.5% and 4.8%, respectively) improved P <.1), and the surgical duration was reduced (91 minutes and 65 minutes, respectively, P <.001).

CONCLUSION

Our findings revealed a continuous reduction of the amount of radiation used by the implementation of a novel ultralow X-ray usage protocol. SFR, complications, and surgical duration all improved, demonstrating that the novel protocol is as effective as current methods. Exposure to ionizing radiation can be significantly reduced if the presented protocol is followed strictly.

New for Old-Coagulum Lithotomy vs a Novel Bioadhesive for Complete Removal of Stone Fragments in a Comparative Study in an Ex Vivo Porcine Model

OBJECTIVES

To evaluate a recently reported new bioadhesive system for the retrieval of small residual fragments (RFs) after intracorporeal lithotripsy, we systematically compared this system with coagulum lithotomy in retrograde intrarenal surgery.

MATERIALS AND METHODS

We extracted 30 human stone fragments (≤1 mm) in an ex vivo porcine kidney model using a flexible ureteroscope for three groups: (1) the novel bioadhesive, (2) autologous blood as a natural adhesive, and (3) (control group) a conventional retrieval basket. Each group consisted of 15 test runs. Outcomes were evaluated regarding the macroscopic stone-free rate (SFR), retrieval time, and number of ureteral passages.

RESULTS

For groups 1 and 2, a significant advantage in stone clearance, mean retrieval time, and number of retrievals was detected compared to the control group (p = 0.001). The time and number of retrievals were significantly lower in group 1 (10:36 minutes, p = 0.001) than in group 2 (26:12 minutes, p = 0.001), with shorter clotting time and better visibility.

CONCLUSIONS

These data show the general feasibility of intrarenal RF embedding to improve the SFR. Our data furthermore suggest the superiority of the artificial bioadhesive embedding agent over the application of native blood. Further in vivo studies and other research are necessary to confirm the adhesive's effect in patients.

[Urinary Stone Analysis - What does the Future Hold in Store?]

Analysis of the composition of a urinary stone is one of the most important steps in the clinical management of patients with urolithiasis. Fourier transform infrared spectroscopy, X-ray diffractometry and petrographic microscopy are the techniques currently used. Novel technical developments in recent years - such as Raman spectroscopy and hyperspectral imaging - have resulted in new approaches to improve urinary stone analysis. In future, table-top portable systems may be used that allow stones to be rapidly examined directly after the operation. These systems may even be integrated into lithotripsy laser systems.

Algorithm-Based Motion Magnification for Video Processing in Urological Laparoscopy

PURPOSE

Minimally invasive surgery is in constant further development and has replaced many conventional operative procedures. If vascular structure movement could be detected during these procedures, it could reduce the risk of vascular injury and conversion to open surgery. The recently proposed motion-amplifying algorithm, Eulerian Video Magnification (EVM), has been shown to substantially enhance minimal object changes in digitally recorded video that is barely perceptible to the human eye. We adapted and examined this technology for use in urological laparoscopy.

MATERIALS AND METHODS

Video sequences of routine urological laparoscopic interventions were recorded and further processed using spatial decomposition and filtering algorithms. The freely available EVM algorithm was investigated for its usability in real-time processing. In addition, a new image processing technology, the CRS iimotion Motion Magnification (CRSMM) algorithm, was specifically adjusted for endoscopic requirements, applied, and validated by our working group.

RESULTS

Using EVM, no significant motion enhancement could be detected without severe impairment of the image resolution, motion, and color presentation. The CRSMM algorithm significantly improved image quality in terms of motion enhancement. In particular, the pulsation of vascular structures could be displayed more accurately than in EVM.

CONCLUSIONS

Motion magnification image processing technology has the potential for clinical importance as a video optimizing modality in endoscopic and laparoscopic surgery. Barely detectable (micro)movements can be visualized using this noninvasive marker-free method. Despite these optimistic results, the technology requires considerable further technical development and clinical tests.

Abstract P2-07-08: Neuroleptics in breast cancer risk

This abstract was not presented at the symposium.

Novel Biocompatible Adhesive for Intrarenal Embedding and Endoscopic Removal of Small Residual Fragments after Minimally Invasive Stone Treatment in an Ex Vivo Porcine Kidney Model: Initial Evaluation of a Prototype

PURPOSE

Residual fragments related to endoscopic intracorporeal lithotripsy are a challenging problem. The impact of residual fragments remains a subject of discussion and growing evidence highlights that they have a central role in recurrent stone formation. Therefore, we developed a novel bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy in an ex vivo porcine kidney model.

MATERIALS AND METHODS

In a standardized setting 30 human stone fragments 1 mm or less were inserted in the lower pole of an ex vivo porcine kidney model. We assessed the extraction efficacy of flexible ureteroscopy using the bioadhesive system in 15 preparations and a conventional retrieval basket in 15. Outcomes were compared regarding the endoscopic and macroscopic stone-free rate, and overall time of retrieval.

RESULTS

Embedding and retrieving the residual fragment-bioadhesive complex were feasible in all trial runs. We observed no adverse effects such as adhesions between the adhesive and the renal collecting system or the instruments used. The stone-free rate was 100% and 60% in the bioadhesive and conventional retrieval groups, respectively (p = 0.017). Mean retrieval time was significantly shorter at 10 minutes 33 seconds vs 36 minutes 56 seconds in the bioadhesive group vs the conventional group (p = 0.001).

CONCLUSIONS

This novel method involving adhesive based complete removal of residual fragments from the collecting system has proved to be feasible. Our evaluation in a porcine kidney model revealed that this technology performed well. Further tests, including inpatient studies, are required to thoroughly evaluate the benefit and potential drawbacks of bioadhesive based extraction of residual fragments after intracorporeal lithotripsy.

Flexible Vesiculovasoscopy Using a Microoptical System in a Human Cadaver Model: An Experimental Approach for Atraumatic Endoscopy of the Seminal Tract

OBJECTIVES

The most common pathologies of the seminal tract are persistent hematospermia, seminal vesicle stones, and seminal duct obstruction. Endoscopic diagnostic work-up of the seminal tract is impeded by complex anatomy and lack of technical equipment. To date, there is no standardized endoscopic approach. The purpose of this study was to investigate the applicability and feasibility of a flexible microoptical device for atraumatic endoscopy of the seminal tract in a male human cadaver.

MATERIALS AND METHODS

The transurethral endoscopic examination was performed on a male cadaver. No premortal interventions or diseases of the genitourinary tract had been reported. The seminal orifice was identified via cystoscopy and accessed by the Seldinger technique using a hydrophilic guidewire and ureteral catheter. Retrograde endoscopic inspection of the distal seminal tract was performed using a miniaturized flexible endoscope. An antegrade endoscopic inspection of the seminal tract was carried out via high scrotal access to the vas deferens.

RESULTS

Structures of the seminal tract, such as the ejaculatory duct, seminal vesicles, and distal portion of the ductus deferentes, were visualized using the miniaturized endoscope. Image quality allowed identification of anatomical structures and characterization of tissue properties. The technical limitations we observed involved the system's maneuverability.

CONCLUSIONS

Initial results of this novel endoscopic approach to the seminal tract using a flexible microoptical system are encouraging. However, considerable anatomical limitations of the targeted organs necessitate further refinements of the technical equipment. This approach might improve diagnostics and treatment of genitourinary diseases. Future surgical techniques may include intraseminal laser therapy or endoocclusion to monitor fertility in men.

Endoscopically Determined Stone Clearance Predicts Disease Recurrence Within 5 Years After Retrograde Intrarenal Surgery

OBJECTIVE

To assess stone-related events (SREs) requiring retreatment in a series of 100 consecutive patients treated by retrograde intrarenal surgery (RIRS) for renal stones and to evaluate potential risk factors thereof.

PATIENTS AND METHODS

The primary outcome was incidence of SRE (medical or surgical treatment). Secondary outcomes included side of SRE, time to SRE, and late complications. Analysis of potential risk factors included high-risk stone formers (HRSFs), obesity, high stone burden, and lower pole stones. In addition, we evaluated endoscopically determined small residual fragments (SRF) of <1 mm (i.e., fragments too small for retrieval) as an independent risk factor.

RESULTS

Eighty-five of the 99 patients were followed up for a mean of 59 months (31-69), among whom 26 (30.1%) had SRE. Thirty-four of the 85 (40%) patients were HRSFs, 22 of whom experienced SRE (both sides) during follow-up (64.7%, p < 0.001). Eight of the 17 patients (47.1%) with SRF experienced ipsilateral side SRE compared with 13 (19.1%) of the 68 without SRF (p = 0.022, hazard ratio 2.823, 95% confidence interval [95% CI] 1.16, 6.85). Risk for ipsilateral SRE was unaffected by the presence of SRF among HRSFs (p = 0.561). Of low-risk patients with SRF, 33.3% experienced ipsilateral SRE, while those without SRF experienced no ipsilateral SRE (p < 0.001).

CONCLUSION

Endoscopically determined stone clearance predicts disease recurrence within 5 years after RIRS. Even SRF are an important risk factor for future stone-related (ipsilateral) events; therefore, patients with residual fragments of any size should not be labeled "stone free" and endoscopic stone treatment should aim at complete stone clearance.

Narrow linewidth, single mode 3 kW average power from a directly diode pumped ytterbium-doped low NA fiber amplifier

We report on a newly designed and fabricated ytterbium-doped large mode area fiber with an extremely low NA (~0.04) and related systematic investigations on fiber parameters that crucially influence the mode instability threshold. The fiber is used to demonstrate a narrow linewidth, continuous wave, single mode fiber laser amplifier emitting a maximum output power of 3 kW at a wavelength of 1070 nm without reaching the mode-instability threshold. A high slope efficiency of 90 %, excellent beam quality, high temporal stability, and an ASE suppression of 70 dB could be reached with a signal linewidth of only 170 pm.

Clinical significance of residual fragments in 2015: impact, detection, and how to avoid them

PURPOSE

Residual fragments are common after stone treatment. Little is known about clinical outcomes relevant to the patient. This comprehensive review of the literature highlights the impact of residual fragments, modes of detection, and treatment strategies to avoid residual fragments in shock wave therapy, ureteroscopy, and percutaneous nephrolithotomy.

METHODS

A comprehensive review of current literature was performed using PubMed(®), MEDLINE(®), Embase™, Ovid(®), Google Scholar™, and the Cochrane Library. Publications relevant to the subject were retrieved and critically appraised.

RESULTS

Residual fragments after treatment for urinary stones have a significant impact on a patient's well-being and future course. (Ultra-) low-dose non-contrast computed tomography detects small residuals most reliably. In shock wave lithotripsy, adherence to basic principles helps to improve results. Various techniques and devices facilitate complete stone clearance in conventional and miniaturized percutaneous nephrolithotomy and (flexible) ureteroscopy. Promising new technologies in shock waves, lasers, and robotics (and potentially microrobotics) are on the horizon.

CONCLUSIONS

Residual fragments are relevant to patients. Contemporary treatment of urolithiasis should aim at complete stone clearance.