Basic and advanced technological evolution of laser lithotripsy over the past decade: An educational review by the European Society of Urotechnology Section of the European Association of Urology

Laser disintegration of urinary stones is a cornerstone of urolithiasis treatment in the modern era. Despite the wide clinical use of stone lasers, basic and advanced technological achievements and developments are difficult to comprehend and interpret by the average urologist. A descriptive analysis of laser production and stone disintegration mechanisms was performed. We focused on physics of modern types of lithotripters, the construction of laser fibers, laser parameters, new modes, settings, and lithotripsy techniques. The main principle of laser emission remains the same since the first emitting laser was produced. Peak power density and short interaction time lead to photothermal effects responsible for stone disintegration. Modern lithotripters such as Holmium: YAG (low/high power, Moses technology) and thulium fiber laser show basic construction differences with the physical properties of the latter being superior, at least in in vitro studies. By adjusting lasing parameters, a wide spectrum of stone ablation from fragmentation to dusting can be achieved. New technology allows for the production of real dust. Knowledge of laser fiber construction and physical properties are useful in marketing and clinical use. Urologists should understand the physical and physiological background of the lasers used in their everyday practice for stone fragmentation.

Natural History of Post-Treatment Kidney Stone Fragments: A Systematic Review and Meta-Analysis

PURPOSE

We assessed the literature around post-treatment asymptomatic residual stone fragments and performed a meta-analysis. The main outcomes were intervention rate and disease progression.

MATERIALS AND METHODS

We searched Ovid®, MEDLINE®, Embase™, the Cochrane Library and ClinicalTrials.gov using search terms: "asymptomatic", "nephrolithiasis", "ESWL", "PCNL", "URS" and "intervention." Inclusion criteria were all studies with residual renal fragments following treatment (shock wave lithotripsy, ureteroscopy or percutaneous nephrolithotomy). Analysis was performed using 'metafor' in R and bias determined using Newcastle-Ottawa scale.

RESULTS

From 273 articles, 18 papers (2,096 patients) had details of intervention rate for residual fragments. Aggregate intervention rates for ≤4 mm fragments rose from 19% (20 months) to 22% (50 months), while >4 mm fragments rose from 22% to 47%. Aggregate disease progression rates for ≤4 mm rose from 25% to 47% and >4 mm rose from 26% to 88%. However, there was substantial difference in definition of "disease progression." Meta-analysis comparing >4 mm against ≤4 mm fragments: intervention rate for >4 mm (vs ≤4 mm): OR=1.50 (95% CI 0.70-2.30), p <0.001, I²=67.6%, tau²=0.48, Cochran's Q=11.4 (p=0.02) and Egger's regression: z=3.11, p=0.002. Disease progression rate for >4 mm: OR=0.06 (95% CI -0.98-1.10), p=0.91, I²=53.0%, tau²=0.57, Cochran's Q=7.11 (p=0.07) and Egger's regression: z=-0.75, p=0.45. Bias analysis demonstrated a moderate risk.

CONCLUSIONS

Larger post-treatment residual fragments are significantly more likely to require further intervention especially in the long term. Smaller fragments, although less likely to require further intervention, still carry that risk. Notably, there is no significant difference in disease progression between fragment sizes. Patients with residual fragments should be appropriately counselled and informed decision-making regarding further management should be done.

First In-Human Burst Wave Lithotripsy for Kidney Stone Comminution: Initial Two Case Studies

Purpose: To test the effectiveness (Participant A) and tolerability (Participant B) of urinary stone comminution in the first-in-human trial of a new technology, burst-wave lithotripsy (BWL). Materials and Methods: An investigational BWL and ultrasonic propulsion system was used to target a 7-mm kidney stone in the operating room before ureteroscopy (Participant A). The same system was used to target a 7.5 mm ureterovesical junction stone in clinic without anesthesia (Participant B). Results: For Participant A, a ureteroscope inserted after 9 minutes of BWL observed fragmentation of the stone to <2 mm fragments. Participant B tolerated the procedure without pain from BWL, required no anesthesia, and passed the stone on day 15. Conclusions: The first-in-human tests of BWL pulses were successful in that a renal stone was comminuted in <10 minutes, and BWL was also tolerated by an awake subject for a distal ureteral stone. Clinical Trial NCT03873259 and NCT02028559.

Outcomes of extracorporeal shock wave lithotripsy for ureteral stones according to ESWL intensity

Background

We evaluated the treatment outcomes of ureteral stones according to energy intensity generated by extracorporeal shock wave lithotripsy (ESWL).

Methods

We retrospectively analyzed 150 patients who underwent ESWL for treatment of ureteral stones between September 2018 and February 2020. All stones were confirmed by a computed tomography examination, and the size, location, skin-to-stone distance, and Hounsfield units (HU) of the stones were assessed. In addition, patient characteristics including body mass index and estimated glomerular filtration rate, which can affect treatment outcome, were also evaluated. The success or failure of ESWL was confirmed according to the session, and the factors affecting the treatment outcome were analyzed using a logistic regression model.

Results

Of the 150 patients, 82 (54.7%) had stones in the proximal ureter, 5 (3.3%) in the mid, and 63 (42.0%) in the distal ureter. Patients underwent ESWL an average of 1.5 times, and the success rate according to session was 65.3% for the first, 83.3% for the second, and 90.0% for the third session. A multivariate analysis revealed that stone size [odds ratio (OR) 0.81, 95% confidence interval (CI), 0.66–0.99, P=0.049] and HU (OR 0.99, 95% CI, 0.98–0.99, P=0.001) were significant factors affecting the success rate after the first ESWL session; ESWL intensity was not related to success rate. Stone size (OR 0.78, 95% CI, 0.62–0.96, P=0.022) was the only significant factor affecting the success rate in the third session.

Conclusions

Stone size and HU affected the ESWL success rate. ESWL intensity was not significantly related to the success rate, so it should be adjusted according to patient pain and the degree of stone fragmentation.

Ultrasound Diagnosis and Active Ureteroscopy for Obstructive Ureteral Calculi during Pregnancy: Multicenter Experience

Objectives: To evaluate the safety and efficacy of ultrasound (US) and primary ureteroscopy (URS) in the management of symptomatic obstructive ureteric stones during pregnancy. Patients and Methods: A prospective multicenter study was performed between June 2013 and December 2019, including all consecutive pregnant patients admitted to three urology centers with intractable renal colic with obstructed ureter secondary to obstructive ureteral calculi. Color Doppler ultrasound was used to evaluate renal Resistive Index (RI) and ureter jet. Primary URS was performed to remove the blocking stones. The safety and effectiveness of the procedures were assessed, as well as the stone-free rate (SFR) and the condition of the upper tract after delivery. Results: A total of 111 pregnant patients were included with a mean age of 27.4 ± 4.4 years and a mean renal RI of 0.78 ± 0.02. US diagnosed stones in 46.8% of patients, while 100 (90%) patients had altered lower ureter urinary jet, including 86.5% who had URS-confirmed ureteric stones; SFR was 95.8% with no serious urologic, fetal, or obstetric complications. Nine percent of patients had premature delivery, which was significantly correlated with postoperative urinary tract infection and premature uterine contraction (p ˂ 0.0001). In the third-month follow-up of US, all patients showed no residual hydronephrosis. Postoperative follow-up procedures were required in 15.3% of patients. Conclusion: Obstructive ureteral stones during pregnancy can be detected safely and appropriately with a combined elevated renal RI and absent ureteral jet detected by Doppler US. Definitive URS is an efficient and safe alternative option for those who fail in conservative management.

Coronary intravascular lithotripsy for coronary artery calcifications- systematic review of cases

Background: Coronary artery calcification (CAC) is a pathological deposition of calcium in the intimal and medial layer of the arterial wall. A plethora of therapeutic calcium debulking techniques is available for the treatment of CAC, including orbital or rotational atherectomy, excimer lasers, cutting, and scoring balloons, which are associated with a soaring rate of complication and low efficacy. To this end, in 2016, the Food and Drug Administration (FDA) posited that shockwave intravascular lithotripsy (S-IVL) technique can be employed with minimal complication.

Methods: A retrospective review of cases received lithotripsy for calcified coronary artery disease was performed by using online data from PubMed, Embase, and the Cochrane Central Register of Controlled Trials. The available search results were downloaded into an Endnote library and analyzed into two phases.

Results: Out of 24 participants from case reports and series, Majority were found to be Male. There was no significant difference found in the mortality of patients undergoing IVL for the stenosis of the left main stem, left anterior descending, left circumflex artery, or diagonal branch. The mortality was found to be high among 6 patients with prior comorbidities and underwent more than 3 cycles of IVL (OR 37,95% Cl 1.54–886.04, P 0.02). Out of 24 patients, 2 (8.33%) patients developed complications such as vessel dissection (OR 3.4, 95% Cl 17.87–64.68, P 0.4).

Conclusion: Shockwave intravascular lithotripsy (S-IVL) may be used in cases of the calcified disease to gain vessel lumen in order to deploy drug-eluting stents with PCI. The success of the DES implantation of IVL can be 100% with a minimal complication rate.

The Role of Cavitation in Energy Delivery and Stone Damage During Laser Lithotripsy

Purpose: Although cavitation during laser lithotripsy (LL) contributes to the Moses effect, the impact of cavitation on stone damage is less clear. Using different laser settings, we investigate the role of cavitation bubbles in energy delivery and stone damage. Materials and Methods: The role of cavitation in laser energy delivery was characterized by using photodetector measurements synced with high-speed imaging for laser pulses of varying durations. BegoStone samples were treated with the laser fiber oriented perpendicularly in contact with the stone in water or in air to assess the impact of cavitation on crater formation. Crater volume and geometry were quantified by using optical coherence tomography. Further, the role of cavitation in stone damage was elucidated by treatment in water with the fiber oriented parallel to the stone surface and by photoelastic imaging. Results: Longer pulse durations resulted in higher energy delivery but smaller craters. Stones treated in water resulted in greater volume, wider yet shallower craters compared with those treated in air. Stones treated with the parallel fiber showed crater formation after 15 pulses, confirmed by high-speed imaging of the bubble collapse with the resultant stress field captured by photoelastic imaging. Conclusions: Despite improved energy delivery, the longer pulse mode produced smaller crater volume, suggesting additional processes secondary to photothermal ablation are involved in stone damage. Our critical observations of the difference in stone damage treated in water vs in air, combined with the crater formation by parallel fiber, suggest that cavitation is a contributor to stone damage during LL.

[Retrograde intrarenal surgery using a 1.94 m superpulsed thulium fiber laser]

INTRODUCTION

surgical treatment of urinary stone disease plays an important role in urological practice. Stone fragmentation can be performed using various lithotripters, from which Holmium fiber laser (Ho: YAG) has currently taken the main place. According to the current literature, a superpulsed thulium fiber laser with a wavelength of 1.94 m and a maximum power output of 40 W showed in vitro higher efficiency compared to Ho: YAG, while having the same safety profile. The use of a thulium fiber laser with a pulse energy of 0.025-6 J and a high repetition rate (up to 1600 Hz) allows to most effectively perform stone dusting during retrograde intrarenal surgery (RIRS).

AIM

to improve the performance of RIRS using the 1.94m superpulsed thulium fiber laser.

MATERIALS AND METHODS

a total of 152 patients with renal stones who were treated during the period from February 2018 to July 2019 were included in the study. The analysis of the laser settings, their effect on retropulsion and visibility when performing RIRS using a superpulsed thulium fiber laser with a wavelength of 1.94 m and a maximum power output of 40 W, a peak power of 500 W, as well as an assessment of the stone-free rate the first postoperative day and 3 months after the procedure was done.

RESULTS

The most frequently used settings were as following: 0.5 J, 30 Hz, 15 W (No. 1), 0.15 J, 200 Hz, 30 W (No. 2), 0.8 J, 31.25 Hz, 25 W (No. 3), 0.8 J, 37.5 Hz, 30 W (No. 4). The statistical analysis of the influence of the settings on the quality of endoscopic imaging and retropulsion was carried out. In addition, the features of each settings were analyzed. The stone-free rate on the first postoperative day was evaluated using low-dose CT.

CONCLUSION

A superpulsed thulium fiber laser with a wavelength of 1.94 m and a maximum power of 500 W has shown high efficiency in clinical practice when performing RIRS, since it allows to have good endoscopic imaging, minimal retropulsion, and to perform stone dusting, which had a positive effect on the stone-free rate. Optimization of the settings of thulium fiber lithotripsy may improve the results of surgical treatment of urinary stone disease.

Ultrasound-Guided Sialendoscopy with Holmium: Yttrium Aluminum Garnet (YAG) Laser Treatment of Parotid Sialolithiasis

BACKGROUND At present, promptly diagnosing sialolithiasis is easy with the assistance of various noninvasive diagnostic procedures. However, the treatment of parotid sialolithiasis remains inadequate. An immense challenge for oral maxillofacial practitioners is the treatment of large radiolucent stones, especially of those that are located in a hard-to-approach positions in the salivary ducts. This case report aims to propose the protocol of a new technique to improve the management of parotid salivary stones. In 2017, our hospital was the first medical center in Vietnam to implement this technique in the treatment of parotid sialolithiasis. CASE REPORT A 38-year-old man was diagnosed with parotid sialolithiasis based on ultrasound and computed tomography (CT) scanning results. He underwent ultrasound-guided sialendoscopy with holmium: yttrium aluminum garnet (YAG) laser lithotripsy. The stone was large (22×12 mm) and in an unfavorable position. A narrow strip of fibrous tissue in front of the stone was also noted. However, 1 week after surgery the patient had local swelling of the parotid gland and no manifestation of inflammation, facial paralysis, or obstructed saliva through the drainage ducts. The patient was examined for clinical symptoms and glandular ultrasound at 3 months and 6 months after the procedure. The follow-up examination results showed normal parotid gland function, no complications or recurrence of stones, and no narrowing of the gland duct. CONCLUSIONS Ultrasound-guided sialendoscopy with holmium: YAG laser is safe and effective for treating parotid salivary gland stones.

Intravascular Ultrasound-Guided Coronary Lithotripsy Treatment of In-Stent Restenosis in Saphenous Venous Graft

To the best of our knowledge, this is the first description of intravascular-ultrasound guided coronary lithotripsy on saphenous vein graft because of severely calcific in-stent restenosis, showing good result without procedural complications.

Conservative Management of Liver Perforation During Percutaneous Nephrolithotomy: Case Couplet Presentation

Percutaneous nephrolithotomy (PCNL) remains the recommended intervention for large kidney stones, major complications, although rare, are between 1% and 7%. Literature regarding liver injury during PCNL is sparse, and many incidences occur unnoticed. In general, most liver injuries can be treated conservatively when compared with other organ injury sustained during PCNL. Despite this, there is still significant potential for intraperitoneal bleeding as well as possible hemodynamic instability that may result secondary to the inadvertent access. Our team describes two cases of liver injury during PCNL with focus on presentation and injury management. Both cases were treated conservatively through close clinical monitoring and delayed removal of nephrostomy tube. Both liver injuries were diagnosed primarily through postprocedure axial CT imaging. In general, risk factors include supracostal access, particularly at or above the 11th rib, as well as hepatomegaly. Despite that liver injury is a rare complication of right-sided PCNL, outcomes can result in significant blood loss not diagnosed. We present in this study two instances of effective conservative management of liver injury after PCNL.

Management of Splenic Injury During Percutaneous Nephrolithotomy: Report of Two Cases

Percutaneous nephrolithotomy (PCNL) has become the standard of care for the removal of kidney stones >2 cm. Major complications, although rare, are between 1% and 7%. Splenic injury during PCNL is rare and can often be managed conservatively, but has the potential to be devastating, necessitating the importance of early diagnosis. Our team describes two cases of splenic injury during PCNL with emphasis on diagnosis and management. Although both cases were managed conservatively through close monitoring and prolonged nephrostomy tube presence, one case had a concurrent pneumothorax. Both cases were diagnosed primarily through postprocedure CT imaging. Risk factors primarily include supracostal access and splenomegaly. Splenic injury is a rare complication that can often be managed conservatively; however, prompt recognition of injury is important. We present in this study two cases of conservative splenic injury management sustained during PCNL.

Clinical Comparison of Super Pulse Thulium Fiber Laser and High-Power Holmium Laser for Ureteral Stone Management

Purpose: To evaluate the efficacy of new super pulse thulium fiber laser (SP TFL) and compare it with holmium laser for ureterolithotripsy. Patients and Methods: A total of 174 patients with solitary ureteral calculi were enrolled in 2016 to 2018. Stone sizes ranged between 0.6 and 2.4 cm. The SP TFL FiberLase U2 and 120H Ho:YAG laser with fibers diameters of 400 and 365 μm, respectively, were used. The laser settings were 1 J × 10 Hz = 10 W for both devices. All patients were randomized into two groups. The age, stone size, location, and density were comparable in both groups. The evaluated parameters were operation time, endoscopic view quality, retropulsion grade, stone-free rate, and complication rate. Results: The total operation time and lasering time were longer in the Ho:YAG group (24.7 ± 0.7 minutes vs 32.4 ± 0.7 minutes, p = 0.05), and postoperative stenting was necessary in one vs four cases, respectively. At 30 days of follow-up, no residual stones were observed in the SP TFL group (vs five cases of Ho:YAG). Conclusion: SP TFL technology was associated with excellent efficacy/safety ratio. The SP TFL may be considered as a viable alternative to Ho:YAG laser stone management.

The clinical and immunological features of the post-extracorporeal shock wave lithotripsy anti-glomerular basement membrane disease

Introduction

Extracorporeal shock wave lithotripsy (ESWL) is a noninvasive modality to treat urolithiasis, with complications including tissue damage and hematoma of kidney parenchyma. Anti-glomerular basement membrane (GBM) disease is suggested to be a rare complication of ESWL since it was reported in several cases to occur after ESWL. However, the clinical and immunological features of the ESWL-associated anti-GBM disease have not been fully investigated so far.

Case Presentation

Here, we present the clinical, pathological, and immunological characteristics of three patients with the post-ESWL anti-GBM disease in our hospital. Anti-GBM disease occurred within a median of 22 months after ESWL treatment. It presented with similar clinical features to the classic anti-GBM disease, including fever, gross hematuria, and rapidly progressive glomerulonephritis (RPGN) with poor renal prognosis. Sera from all patients recognized the α3(IV)NC1 in GBM, but with IgG2 and IgG4 as the dominant IgG subclasses.

Conclusion

Although further exploration is required to prove the causal relationship in this rare condition, our study reminds physicians that patients developing acute renal insufficiency after ESWL should lead to the suspicion of anti-GBM disease and in-time diagnosis and treatment.

Dynamic properties of surfactant-enhanced laser-induced vapor bubbles for lithotripsy applications

SIGNIFICANCE

Water is a primary absorber of infrared (IR) laser energy, and urinary stones are immersed in fluid in the urinary tract and irrigated with saline during IR laser lithotripsy. Laser-induced vapor bubbles, formed during lithotripsy, contribute to the stone ablation mechanism and stone retropulsion effects.

AIM

Introduction of a surfactant may enable manipulation of vapor bubble dimensions and duration, potentially for more efficient laser lithotripsy.

APPROACH

A surfactant with concentrations of 0%, 5%, and 10% was tested. A single pulse from a thulium fiber laser with wavelength of 1940 nm was delivered to the surfactant through a 200-μm-core optical fiber, using a wide range of laser parameters, including energies of 0.05 to 0.5 J and pulse durations of 250 to 2500  μs.

RESULTS

Bubble length, width, and duration with surfactant increased on average by 29%, 17%, and 120%, compared with water only.

CONCLUSIONS

Our study demonstrated successful manipulation of laser-induced vapor bubble dimensions and duration using a biocompatible and commercially available surfactant. With further study, use of a surfactant may potentially improve the "popcorn" technique of laser lithotripsy within the confined space of the kidney, enable non-contact laser lithotripsy at longer working distances, and provide more efficient laser lithotripsy.

Management of Colon Perforation During Percutaneous Nephrolithotomy in Patients with Complex Anatomy: A Case Series

Percutaneous nephrolithotomy (PCNL), first described in 1976, is the gold standard for the management of large kidney stones, with stone-free rates as high as 95% in contemporary literature. Colonic injuries during PCNL are a rare complication with an estimated incidence of 0.3%-0.5%. However, given the high morbidity incurred and the necessity of prompt operative intervention, it is imperative that practitioners have a low suspicion threshold for such injuries, particularly in those patients with altered or complex anatomy. This case series addresses peri- and postoperative outcomes of colon perforation during PCNL in patients with complex anatomy and reviews the technical challenges of surgery with potential methods to avoid injury in the future. Herein we review three instances of colonic injuries and their subsequent management to highlight both the presentation and the optimal management of these rare occurrences.

Saline Solution Irrigation of the Bile Duct after Stone Removal Reduces the Recurrence of Common Bile Duct Stones

Common bile duct (CBD) stone is a relatively common but potentially life-threatening disease. Endoscopic sphincterotomy (EST) has been performed as standard therapy for CBD stones, but the rate of recurrence of CBD stones is high. Risk factors have been poorly defined, and no effective means for the prevention of the recurrence of CBD stones have been established so far. We aimed to identify significant risk factors for the recurrence of bile duct stones. This study included 477 patients (231 women; mean age, 80.5 years) who underwent EST and cleared CBD stones on cholangiography. A retrospective analysis was performed for the consecutively collected data. During the follow-up period of 6-75 months, the recurrence of CBD stones was observed in 99 patients (20.8%). The median time to the recurrence was 19.0 months (range 4-72 months). Multivariate analysis identified the need for mechanical lithotripsy, which was used for stone fragmentation, as a risk factor. Mechanical lithotripsy caused cholangiography-negative small residua. Notably, saline solution irrigation of the bile duct reduced the recurrence of CBD stones. These results demonstrate that subsequent biliary irrigation after stone removal may prevent the recurrence of CBD stones by clearing small residual fragments.

Effect of Chilled Irrigation on Caliceal Fluid Temperature and Time to Thermal Injury Threshold During Laser Lithotripsy: In Vitro Model

Introduction: High-power lasers (100-120 W) have widely expanded the available settings for laser lithotripsy and facilitated tailoring of treatment for individual cases. Previous in vitro and in vivo studies have demonstrated that a toxic thermal dose to tissue can result from treatment within a renal calix. The objective of this in vitro study was to compare thermal dose and time with tissue injury threshold when using chilled (CH) irrigation and room temperature (RT) irrigation. Materials and Methods: A glass tube attached to a 19 mm diameter bulb simulating a renal calix was placed in a 37°C water bath. A 242 μm laser fiber was passed through a ureteroscope with its tip in the center of the glass bulb. A wire thermocouple was placed 3 mm proximal to the ureteroscope tip to measure caliceal fluid temperature. RT at 19°C or CH at 1°C irrigation was delivered at 0, 8, 12, 15, or 40 mL/minute. The laser was activated at 0.5 J × 80 Hz (40 W) for 60 seconds. Thermal dose was calculated using the Sapareto and Dewey t43 methodology with thermal dose = 120 equivalent minutes considered the threshold for thermal tissue injury. Results: At each irrigation rate, CH irrigation produced a lower starting temperature, a lower plateau temperature, and less thermal dose compared with RT irrigation. The threshold of thermal injury was reached after 13 seconds of laser activation without irrigation. With 12 mL/minute irrigation, the threshold was reached in 46 seconds with RT irrigation but was not reached with CH irrigation. Conclusion: As higher power laser lithotripsy techniques become further refined, methods to mitigate and control thermal dose are necessary to enhance efficiency. CH irrigation slows temperature rise, decreases plateau temperature, and lowers thermal dose during high-power laser lithotripsy.

Endoscopic lithotripsy with a SuperPulsed thulium-fiber laser for ureteral stones: A single-center experience

OBJECTIVES

To estimate the efficacy and safety of SuperPulsed thulium-fiber laser ureteral lithotripsy and to identify optimal laser settings.

METHODS

Patients with solitary stones were prospectively included. Lithotripsy was performed with a SuperPulsed thulium-fiber laser (NTO IRE-Polus, Fryazino, Russia) using a rigid ureteroscope 7.5 Ch (Richard Wolf, Knittlingen, Germany). We analyzed the efficacy of lithotripsy by measuring total energy required for stone disintegration, "laser-on" time, ablation speed, ablation efficacy, and energy consumption. Stone retropulsion and visibility were assessed using a three-point Likert scale. Complications were assessed using the Clavien-Dindo classification system.

RESULTS

A total of 149 patients were included. The mean stone density was 985 ± 360 Hounsfield units, the median (interquartile range) stone volume was 179 (94-357) mm³ . The median (interquartile range) total energy was 1 (0.4-2) kJ, and laser-on time 1.2 (0.5-2.7) min. The median (interquartile range) stone ablation speed was 140 (80-279) mm³ /min, energy for ablation of 1 mm³ was 5.6 (3-9.9) J/mm³ and energy consumption was 0.9 (0.6-1) J/min. A correlation was found between retropulsion and the energy used (r = 0.5, P < 0.001). Multivariable analysis showed energy to be a predictor of increased retropulsion (odds ratio 65.7, 95% confidence interval 1.6-2774.1; P = 0.028). No predictors for worse visibility were identified.

CONCLUSION

The SuperPulsed thulium-fiber laser provides effective and safe lithotripsy during ureteroscopy regardless of stone density. Fiber diameter and laser frequency do not influence visibility or safety. Optimal laser settings are 0.5 J × 30 Hz for fragmentation and 0.15 J × 100 Hz for dusting.

Impact of Laser Fiber Diameter and Irrigation Fluids on Induced Bubble Stream Dynamics with Thulium Fiber Laser: An In Vitro Study

Objectives: The Thulium Fiber Laser (TFL) is studied as an alternative to the holmium:yttrium-aluminium-garnet (Ho:YAG) laser for lithotripsy, with the advantage of an induced bubble stream (IBS). This in vitro study compared the TFL's IBS with 150- and 272 μm-core-diameter laser fiber (CDF) and in four irrigant fluids. Methods: A TFL of 50 W (IPG Photonics^©) and 150 and 272 μm-CDF (Boston Scientific^©) were used, comparing nine energies (in the range from 0.025 to 4 J). An experimental setup consisted of a vertically disposed fiber in a cuvette filled with saline, iodinated contrast agent (IOA), human urine, or deionized water (DW) at ambient temperature. High-speed imaging of three consecutive IBS was performed to determine the influence of energy on their maximum length (ML; μm), width (MW; μm), and duration (MD; μs). Fibers were cleaved with ceramic scissors between each experience. Results: The IBS had higher ML and MW and MD with 150CDF than 272CDF. Maximum pulse rate for 150CDF and 272CDF was 2182 and 2000 Hz, respectively. Every maximum power was higher than the technological limit of TFL (>50 W). At equal energy density, 150CDF was associated with lower dimensions and durations. The IBS had higher maximum dimensions in IOA compared with saline solution (SS). Compared with DW and urine, IBS in IOA were longer beyond 500 mJ. Over 25 mJ, IBS were thinner in DW, urine, and SS. The IBS in DW, urine, and SS had similar maximum dimensions. The IBS's duration was higher in IOA compared with DW, urine, and SS, meaning a lower theoretical maximum pulse rate and power in IOA. Conclusion: Lasering with 150CDF fits with lower pulse energies-higher pulse rates settings than 272CDF, such as fine dusting mode. In IOA, Induced Bubbles Streams present higher dimensions and durations than in other studied fluids, related to its higher viscosity. Safety distance and pulse rate should be increased and decreased, respectively.

Association between ureteric stent dwell time and urinary tract infection

BACKGROUND

Ureteric stone obstruction commonly presents to the emergency department, with definitive management often involving ureteroscopy and laser lithotripsy. Insertion of a ureteric stent prior to staged lithotripsy is commonly performed in the public healthcare system. Foreign bodies in the urinary tract are also known to increase urinary tract infection (UTI) risk. This study aims to evaluate the association between stent dwell time and UTI prior to lithotripsy.

METHODS

The medical records of all patients who were treated for ureteric stones with initial stent insertion and staged lithotripsy, from 1 January 2018 to 30 June 2019 at a single tertiary centre, by eight urologists were retrospectively reviewed. Demographic features, disease factors and urine culture data were collected and analysed.

RESULTS

Of the 172 patients (median age 56.7 years) identified, one-third had a positive pre-stent urine culture. Twenty-three percent had a positive pre-lithotripsy urine culture with 38% of females compared with 15% of males having a positive culture (P = 0.001). Only 4.3% of patients had a pre-lithotripsy UTI when the stent dwell time was less than 1 month compared with 26.2% when ureteric stents were in situ for longer than 1 month (P = 0.021). The correlation between ureteric stent dwell time and pre-lithotripsy UTI was not linear. Patient comorbidities, stone size, burden and location were not statistically correlated to pre-lithotripsy UTI.

CONCLUSION

In delayed two-staged surgical management of acute urolithiasis, optimal ureteric stent dwell time is less than 1 month to reduce pre-lithotripsy UTI. Female gender is an independent risk factor for pre-lithotripsy UTI.

Guideline of guidelines for kidney and bladder stones

Urological organizations publish detailed evidence-based guidelines to support the urologists in the management of urolithiasis. Our objective was to provide clear guidance on the management of urolithiasis, compare the American Urological Association (AUA) and European Association of Urologists (EAU) guidelines, and present an algorithm for different clinical scenarios. The latest AUA and EAU guidelines on urolithiasis were evaluated for the level of evidence and grade of recommendation. All recommendations on management of urolithiasis (surgical and medical management) were reviewed and included. Both the organizations provide guidance for initial patient assessment, imaging requirements, and therapeutic options, including surgical intervention and medical therapy. In addition, these guidelines provide advice for managing specific patient groups, including pediatric patients and pregnant patients. Although there is a general concordance between both the groups, differences exist particularly for recommended modality of surgical intervention depending on stone location and size. Although both the guidelines were broadly similar, we also highlighted the variations in the level of evidence and grade of recommendation. Although these guidelines provide a valuable evidence-based framework to support the management of urinary tract stones, their implementation must be tailored to individual patient needs and available resources.

Flexible ureteroscopy and laser lithotripsy for renal stones 2 cm or greater: A single institutional experience

With improvements in endoscopy and laser technology, flexible ureteroscopy (FURS) has been a viable treatment option for large renal stones. Here, we share our experience of the FURS treatment for renal stones 2 cm or greater.We evaluated 251 consecutive patients who underwent FURS and holmium laser lithotripsy for renal stones 2 cm or greater between January 2015 and April 2019. Stone size was defined as the longest axis on non-contrast computed tomography. Data were retrospectively collected from electronic medical records. Patient demographics, stone clearance rates and perioperative complications were evaluated.There were 165 male patients and 86 female patients with an average age of 46.9 years (range 22-80 years). Mean stone size was 2.7 cm and the average number of procedures was 1.4 (range 1-5). The stone-free rate at the end of the first, second and third procedure was 61.9%, 82.9%, and 89.5%, respectively. The final stone-free rate decreased as stone size grows, and it was only 58.3% for kidney stones larger than 4 cm after an average of 2.3 procedures. The lowest clearance rates were observed in lower calyx calculi (87.2%) and multiple calyx calculi (83.5%). The overall complication rate was 15.1%, and the most common complication was postoperative fever (9.6%). One patient required blood transfusion, owing to postoperative coagulation disorders induced by urosepsis.Single or staged FURS is a practical treatment option for the renal stones sized 2 to 4 cm with acceptable efficacy and safety. Stone clearance rate of FURS treatment is mainly affected by stone size and location.

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

Purpose: The purpose of the study is to develop and validate a novel clinical–radiomics nomogram model for pre-operatively predicting the stone-free rate of flexible ureteroscopy (fURS) in kidney stone patients.

Patients and Methods: Altogether, 2,129 fURS cases with kidney stones were retrospectively analyzed, and 264 patients with a solitary kidney stone were included in a further study. For lower calyx calculi, a radiomics model was generated in a primary cohort of 99 patients who underwent non-contrast-enhanced computed tomography (NCCT). Radiomics feature selection and signature building were conducted by using the least absolute shrinkage and selection operator (LASSO) method. Multivariate logistic regression analysis was employed to build a model incorporating radiomics and potential clinical factors. Model performance was evaluated by its discrimination, calibration, and clinical utility. The model was internally validated in 43 patients.

Results: The overall success rate of fURS was 72%, while the stone-free rate (SFR) for lower calyx calculi and non-lower calyx calculi was 56.3 and 90.16%, respectively. On multivariate logistic regression analysis of the primary cohort, independent predictors for SFR were radiomics signature, stone volume, operator experience, and hydronephrosis level, which were all selected into the nomogram. The area under the curve (AUC) of clinical–radiomics model was 0.949 and 0.947 in the primary and validation cohorts, respectively. Moreover, the calibration curve showed a satisfactory predictive accuracy, and the decision curve analysis indicated that the nomogram has superior clinical application value.

Conclusion: In this novel clinical–radiomics model, the radiomics scores, stone volume, hydronephrosis level, and operator experience were crucial for the flexible ureteroscopy strategy.

Combined use of intravascular lithotripsy and brachytherapy: A new approach for the treatment of recurrent coronary in-stent restenosis

Treatment of coronary in-stent restenosis (ISR) is challenging and often requires combination of multiple treatment modalities. Coronary intravascular lithotripsy (IVL) has been successfully used for treating stent under-expansion, but is not currently commercially available in the United States. We present three recurrent coronary ISR cases in which multiple treatment modalities (high-pressure balloon inflation, plaque modification balloons, and laser with contrast injection) failed. These patients were treated with a combination of IVL (peripheral IVL catheter used off-label in the coronary arteries) and brachytherapy. Due to the high IVL balloon profile, delivery via femoral or radial access was challenging, requiring 7-8 French guide catheters. IVL was performed delivering 4-8 treatments of 20 pulses each with a favorable final angiographic and intravascular ultrasound result. All patients were angina free 1 month after the procedure.