Shock wave lithotripsy: the new phoenix?

Factors influencing the efficacy of ultrasound-guided extracorporeal shockwave lithotripsy in the treatment of ureteral stones: a retrospective study

The aim of the study was to analyze the factors influencing the efficacy of ultrasound-guided extracorporeal shockwave lithotripsy (ESWL) in the treatment of ureteral stones. The clinical data of 8102 patients (6083 men and 2019 women) who presented with ureteral stones were retrospectively analyzed. All the patients were treated with ultrasound-guided ESWL. The stone-free rate (SFR) was calculated to evaluate the effect of ESWL. The characteristics of the patients and their stones, and the ESWL parameters applied were compared to identify the factors affecting the treatment outcomes. The SFR and that following one ESWL session were 94.6% (7663/8102) and 75.4% (6107/8102), respectively. Multivariate analysis showed that stone location (OR 0.656, p < 0.001), stone size (OR 1.103, p < 0.001), and degree of hydronephrosis (OR 1.952, p < 0.001) independently affected SFR; and age (OR 1.005, p = 0.022), stone location (OR 0.729, p < 0.001), stone size (OR 1.103, p < 0.001), degree of hydronephrosis (OR 1.387, p = 0.001), maximum energy level(OR 0.691, p < 0.001) independently affected SFR following one session. Ultrasound-guided ESWL is effective in all levels of ureteral stones. Large stone size and moderate hydronephrosis are correlated with treatment failure. Ultrasound-guided ESWL may be the first choice for distal ureteral stones.

Peri-Ureteral Abscess Formation Following Ureteroscopic Laser Lithotripsy: A Case Report

We report the case of a patient with a previous history of obstructive renal calculus disease who initially presented with a symptomatic calculus in her right mid-ureter, requiring ureteroscopy with laser lithotripsy and ureteral stent placement. Shortly after the removal of the stent, the patient was found to have a peri-ureteral abscess, necessitating percutaneous drainage by interventional radiology, and placement of an additional ureteral stent. Adverse reactions to these procedures are rare and, to our knowledge, this is the only documented case of peri-ureteral abscess as a complication of ureteroscopic laser lithotripsy or of ureteral stenting. In addition to developing a peri-ureteral abscess, this patient also experienced deep vein thrombosis (DVT) and subsegmental pulmonary embolism (PE), which also have not been found to be a common complication of laser lithotripsy or ureteral stent placement in any of the studies that we reviewed for this article. The complications that were previously rare are unfortunately on the rise, possibly in the setting of both increased access to invasive therapies as well as the increased rates of diabetes and obesity. Survivability hinges on prompt recognition and treatment of these complications. In the event that a peri-ureteral abscess is discovered, prompt treatment with broad-spectrum antibiotics is recommended in addition to interventional radiology and urology consultation. Antibiotics should cover conventional intra-abdominal and urologic abscess regimens.

Importance of precise imaging for stone identification during shockwave lithotripsy: a critical evaluation of "OptiVision" as a post-processing radiography imaging modality

To evaluate the efficacy of a unique imaging software "OptiVision" on the confidence of stone identification using X-ray imaging during shockwave lithotripsy. A total of 57 patients with solitary radio-opaque kidney stones sized < 15 mm were included and evaluated with appropriate radiological imaging and laboratory studies before undergoing shockwave lithotripsy (SWL). The size of the stones was measured on KUB and CT images using maximal stone diameters. All patients were evaluated with radiography on the Dornier Delta III immediately before SWL and at the end of the SWL session with fluoroscopy, a snapshot image, and the OptiVision modality (applied over the acquired snapshot image without additional radiation exposure) for precise identification of the stone. All images obtained with these three different imaging modalities (fluoroscopy, snapshot, and OptiVision) were comparatively evaluated for confidence levels in stone identification using a five-point Likert scale (1 = poor diagnostic confidence, 5 = excellent diagnostic confidence). These confidence levels were also used to differentiate between stones and bony structures using these same imaging modalities. Results were evaluated for statistical significance regarding their impact on the precise identification of renal stones. A total of 57 patients with solitary stones were evaluated using flouroscopy, snapshot, and OptiVision images before and after SWL to ascertain the efficacy of these 3 imaging modalities on the precise identification of the calculi. Stone sizes ranged from 4 to 15 mm, with a mean of 8.30 mm in the longest dimension. Evaluation of the findings demonstrated that while the pre- and post-SWL confidence of fluoroscopic stone identification was from 29.51 to 31.15%, the values using snapshot ranged from 31.15 to 39.34%. Pre- and post-SWL confidence of stone identification with OptiVision post-processing imaging was approximately 89%. In the majority of cases (n = 43), the use of OptiVision image processing enabled urologists to identify the stone with a higher level of confidence rating than the use of both fluoroscopy (n = 0) and snapshot (n = 0) image processing tools. While a rating level of 4 or higher was given in 89% of images obtained by OptiVision during the pre- and post-SWL phase, this value was only 37% (4 or more points) using fluoroscopy and Snapshot image processing techniques. For all the radiography image processing tools, the distribution of the Likert score differed significantly among the OptiVision, fluoroscopy, and snapshot imaging modalities (p < 0.001). Precise and reliable identification of stone(s) located in the kidney is essential in delivering shock waves to the desired focal point and achieving higher stone-free rates. Our findings demonstrated that using the specially designed imaging modality OptiVision was significantly helpful in identifying and localizing stones with high-quality images before SWL for effective stone disintegration during this procedure.

In-vitro comparison of two electromagnetic shock-wave generators: low-pressure-wide focus versus high-pressure small focus - the impact on initial stone fragmentation and final stone comminution

CONTEXT

Recently developed concepts for higher efficacy ESWL with low-pressure wide focus systems resulting in finer fragmentation of the calculi.

OBJECTIVE

To compare two different electromagnetic shock wave sources (low-pressure wide focus (XL) versus high-pressure small focus (SL)) by sound-field measurements and in-vitro fragmentation.

EVIDENCE ACQUISITION

The CS-2012A XX-ES lithotripter (self-focusing electromagnetic shock-wave generator with concave spherical curved electrical coil; Xinin Lithotripter = XL) was compared to the Siemens Lithoskop (= SL) (electromagnetic generator with a flat electric coil with an acoustical lens). Different sound-field measurements were performed using a fiber-optic hydrophone. Measurements at three different power settings (XL: 8.0kV, 9.3kV and 10.3kV; SL: Level 1, 5 and 8). 10 ATS-stones and 15 BegoStones (9.3 kV, Level 3) with a frequency of 90/minute (SL) and 20/minute (XL). Number of impulses to the first crack and for complete stone comminution (residual fragments <2mm) were documented.

RESULTS

The median number of shock waves for the first crack in ATS-stones with the XL was 12 (10-14), with the SL 7 (6-9). Complete disintegration was accomplished after 815 (782-824) shock waves with XL, 702 (688-712) with SL. The difference was not statistically significant. The median number of shock waves to produce the first crack in BegoStones was 524 (504-542) with XL and only 151 (137-161) with SL. Numbers of shock waves for complete disintegration did not differ significantly (XL:2518 vs SL:2287). Using a wide focus with low pressure shows more homogeneous disintegration.

CONCLUSION

Two stone models showed significant differences regarding form and time of the initial fragmentation. Impulses for stone comminution did not differ significantly. The advantages of a low-pressure wide focus-system include minimal trauma and a homogeneous fragment size but is more time consuming. High-pressure small focus systems are clinically effective.

Can a Dinosaur Think? Implementation of Artificial Intelligence in Extracorporeal Shock Wave Lithotripsy

Background

Extracorporeal shock wave lithotripsy (ESWL) of kidney stones is losing ground to more expensive and invasive endoscopic treatments.

Objective

This proof-of-concept project was initiated to develop artificial intelligence (AI)-augmented ESWL and to investigate the potential for machine learning to improve the efficacy of ESWL.

Design, setting, and participants

Two-dimensional ultrasound videos were captured during ESWL treatments from an inline ultrasound device with a video grabber. An observer annotated 23 212 images from 11 patients as either in or out of focus. The median hit rate was calculated on a patient level via bootstrapping. A convolutional neural network with U-Net architecture was trained on 57 ultrasound images with delineated kidney stones from the same patients annotated by a second observer. We tested U-Net on the ultrasound images annotated by the first observer. Cross-validation with a training set of nine patients, a validation set of one patient, and a test set of one patient was performed.

Outcome measurements and statistical analysis

Classical metrics describing classifier performance were calculated, together with an estimation of how the algorithm would affect shock wave hit rate.

Results and limitations

The median hit rate for standard ESWL was 55.2% (95% confidence interval [CI] 43.2–67.3%). The performance metrics for U-Net were accuracy 63.9%, sensitivity 56.0%, specificity 74.7%, positive predictive value 75.3%, negative predictive value 55.2%, Youden’s J statistic 30.7%, no-information rate 58.0%, and Cohen’s κ 0.2931. The algorithm reduced total mishits by 67.1%. The main limitation is that this is a proof-of-concept study involving only 11 patients.

Conclusions

Our calculated ESWL hit rate of 55.2% (95% CI 43.2–67.3%) supports findings from earlier research. We have demonstrated that a machine learning algorithm trained on just 11 patients increases the hit rate to 75.3% and reduces mishits by 67.1%. When U-Net is trained on more and higher-quality annotations, even better results can be expected.

Patient summary

Kidney stones can be treated by applying shockwaves to the outside of the body. Ultrasound scans of the kidney are used to guide the machine delivering the shockwaves, but the shockwaves can still miss the stone. We used artificial intelligence to improve the accuracy in hitting the stone being treated.

Structure Types of Kidney Stones and Their Susceptibility to Shock Wave Fragmentation

Background:

The modern approach in the treatment of urolithiasis involves the use of non-invasive and minimally invasive techniques based on the stone fragmentation, among which shock wave lithotripsy (SWL) is considered as the first-line treatment for kidney stones < 2 cm and proximal ureter stones.

Objective:

To study the microstructure and mineral composition of kidney stones and to evaluate their influence on the stones’ susceptibility to fragmentation by shock waves.

Methods:

The microstructure and mineral composition of kidney stone samples obtained from shock wave lithotripsy in 87 patients were studied using crystal optical analysis and infrared spectroscopy. The volume fraction of amorphous and crystalline phases of the stone composition, the quantitative and qualitative composition of mineral components were assessed. The fragmentation features of stones with different microstructure were retrospectively analyzed based on the total number of shock waves required for complete stone fragmentation.

Results:

Three kidney stone structure types were identified: amorphous-crystalline structure stones predominantly including the amorphous phase (type A); amorphous-crystalline structure stones predominantly including the crystalline phase (type B); fully crystalline structure stones (type C). Significant positive correlation between the total number of shock waves required for complete stone fragmentation and the volume fraction of crystalline phase was found.

Conclusion:

The structure type of kidney stones is determined by the volume ratio between the amorphous and crystalline phases of their composition. The amorphous-crystalline structure stones with the predominant content of the amorphous phase are more sensitive to shock-wave exposure. The increase in the volume fraction of crystalline phase in the stone structure reduces the stone’s susceptibility to fragmentation by shock waves.

Extracorporeal shock-wave lithotripsy: is it still valid in the era of robotic endourology? Can it be more efficient?

PURPOSE OF REVIEW

The aim of the article is to evaluate the actual role of extracorporeal shock-wave lithotripsy (ESWL) in the management of urolithiasis based on the new developments of flexible ureterorenoscopy (FURS) and percutaneous nephrolithotomy (PCNL).

RECENT FINDINGS

In Western Europe, there is a significant change of techniques used for treatment of renal stones with an increase of FURS and a decrease of ESWL. The reasons for this include the change of indications, technical improvement of the endourologic armamentarium, including robotic assistance. Mostly relevant is the introduction of digital reusable and single-use flexible ureterorenoscopes, whereas micro-PCNL has been abandoned. Some companies have stopped production of lithotripters and novel ideas to improve the efficacy of shock waves have not been implemented in the actual systems. Promising shock-wave technologies include the use of burst-shock-wave lithotripsy (SWL) or high-frequent ESWL. The main advantage would be the very fast pulverization of the stone as shown in in-vitro models.

SUMMARY

The role of ESWL in the management of urolithiasis is decreasing, whereas FURS is constantly progressing. Quality and safety of intracorporeal shock-wave lithotripsy using holmium:YAG-laser under endoscopic control clearly outweighs the advantages of noninvasive ESWL. To regain ground, new technologies like burst-SWL or high-frequent ESWL have to be implemented in new systems.

The effect of focus size and intensity on stone fragmentation in SWL on a piezoelectric lithotripter

Purpose

We aim to analyze the efficacy of different focus sizes and the influence of pulse pressure (intensity) during shock wave lithotripsy (SWL) in terms of stone fragmentation.

Methods

Combination of three focal sizes (F1 = 2 mm, F2 = 4 mm, F3 = 8 mm) and 11 output pressure settings (intensity 10–20) of a piezoelectric lithotripter (Wolf PiezoLith 3000) were tested on artificial stones (n = 99). The stones were placed within a 2 mm mesh cage. The needed number of shockwaves (SW) to first visible crack, 50% and 100% stone disintegration were recorded.

Results

Similar number of SW’s were observed until the first crack 10, 11 and 11 SW’s for F1, F2, and F3, respectively (p > 0,05). The median number of SW needed for 50% stone disintegration was 245 for F1 group, 242 for F2 group and 656 for F3 group. F1 vs F2 p = 0.7, F1 vs F3 and F2 vs F3 p < 0.05. Similarly, with larger focus size a higher number of shockwaves were necessary for 100% stone disintegration. 894, 877 and 1708 SW’s for F1, F2 and F3, respectively. Only for F1 vs F3 and F2 vs F3 (all p < 0.05) a statistical difference was observed. These findings were consistent in all different power settings, with an increased difference in lower power levels (≤ 14).

Conclusions

A smaller focus size, as well as a higher peak pressure results in a more effective stone fragmentation. However, these results need to be confirmed in an in vivo setting with multiple parameters interfering the efficacy, like BMI, respiration or stone migration.

Extracorporeal shock wave lithotripsy versus flexible ureterorenoscopy in the treatment of untreated renal calculi

Background

The reported success rates for treatments of kidney stones with either extracorporeal shock wave lithotripsy (ESWL) or flexible ureterorenoscopy (URS) are conflicting. We aimed to compare the efficacy and safety of ESWL and URS for previously untreated renal calculi.

Methods

All patients treated with ESWL or URS at our tertiary care centre between 2003 and 2015 were retrospectively identified. Patients with previously untreated kidney stones and a stone diameter of 5–20 mm were included. Stone-free, freedom from reintervention and complication rates were recorded. Independent predictors of stone-free and freedom from reintervention rates were identified by multivariable logistic regression and a propensity score-matched analysis was performed.

Results

A total of 1282 patients met the inclusion criteria, of whom 999 (78%) underwent ESWL and 283 (22%) had URS. During post-operative follow-up, only treatment modality and stone size could independently predict stone-free and freedom from reintervention rates. After propensity score matching, ESWL showed significantly lower stone-free rates [ESWL (71%) versus URS (84%)] and fewer patients with freedom from reintervention [ESWL (55%) versus URS (79%)] than URS. Complications were scarce for both treatments and included Clavien Grade 3a in 0.8% versus 0% and Grade 3b in 0.5% versus 0.4% of ESWL and URS treated patients, respectively.

Conclusions

Treatment success was mainly dependent on stone size and treatment modality. URS might be the better treatment option for previously untreated kidney stones 5–20 mm, with similar morbidity but higher stone-free rates and fewer reinterventions than ESWL.

[What is the current status of shock wave lithotripsy?]

BACKGROUND

Shock wave lithotripsy (SWL) became the therapy of choice for the majority of patients with urolithiasis early after its introduction in the early 1980s. Since then, SWL remains the only noninvasive therapy modality for the treatment of urinary stones. Although lithotripters became more versatile and affordable-making them available worldwide-indications for SWL have shifted as well. In most western countries, endoscopic techniques took the lead in stone therapy due to high (early) stone-free and better reimbursement rates. Notwithstanding SWL remains the first-line therapy for most intrarenal and many ureteral stones.

PURPOSE

This contemporary review illuminates technical aspects and improvements of lithotripsy over recent years in context with the current guideline recommendations.

RESULTS

Technical advances in lithotripsy such as shock wave generation, focusing, coupling, stone localization and modifications in therapy regimens are reviewed and presented.

CONCLUSIONS

Urologists are recommended to carefully select the appropriate therapy modality for a patient with urolithiasis. A more comprehensive understanding of the physics of shock waves could lead to much better results, thus, endorsing SWL as first-line therapy for urolithiasis instead of contemporary endourology treatment options.

Combination of extracorporeal lithotripsy and flexible ureterorenoscopy optimize renal lithiasis therapy

OBJECTIVE

Describe our initial experience in the treatment of renal lithiasis with extracorporeal lithotripsy controlled by simultaneous flexible ureterorenoscopy and combined with holmium laser lithotripsy.

MATERIAL AND METHODS

We performed this novel technique in a previously selected patient with left renal lithiasis, two in the superior calix, two in the medium calix and two in the inferior calix, the biggest of which was placed in medium calix and was 6mm long. We proceeded to an extracorporeal shock wave lithotripsy and a simultaneous flexible ureterorenoscopy for better controlling the fragmentation of the lithiasis with the use of a holmium laser. In the immediate post-operative, an ultrasound was performed and, one month later, a computerized tomography (CT) was done.

RESULTS

The complete fragmentation of all the lithiasis was obtained and a double-J catheter was placed. After the assessment of the absence of stone fragments by CT the catheter was removed. No intra-operative or post-operative complications were described.

CONCLUSIONS

The technique described is novel, safe and reproducible. The good result obtained through this combined technique increases our interest in continuing with its application and consider it as an option for the treatment of renal lithiasis in our patients.

Can we predict the need for intervention in steinstrasse following shock wave lithotripsy?

Introduction:

Steinstrasse (SS) is a known complication of shock wave lithotripsy (SWL). Although the majority of SS clears spontaneously, about 6% require intervention. This study was carried out to identify the factors that determine the need for intervention in SS.

Materials and Methods:

This was a retrospective study of all patients who developed steinstrasse following SWL at our center. They were divided into two groups: a) Those cleared spontaneously and b) Those required intervention. The two groups were compared with regard to demographic profile, stone factors and factors related to steinstrasse.

Results:

Out of 2436 cases of SWL, 89 (3%) formed steinstrasse. The majority of the patients (35%) who required intervention had stone sizes of 10-14 mm. Coptcoat type III steinstrasse required significantly more interventions for clearance (P = 0.001). The site and the size of the SS was not a predictor of intervention for SS.

Conclusions:

Early intervention is warranted in patients with steinstrasse where the lead fragment is >5 mm (Coptcoat type III).

Shifting the Split Reflectors to Enhance Stone Fragmentation of Shock Wave Lithotripsy

Shock wave lithotripsy (SWL) has been used widely in urology for about three decades to treat kidney calculi. Technical development to improve performance (i.e., stone fragmentation efficiency) is continuous. Low-pressure wide-focus lithotripters have already achieved promising results. In this study, the lithotripter field and profile of lithotripter shock waves were changed simultaneously using a cost-effective and convenient design. An intact parabolic reflector was split into four pieces, and each part was moved individually. By shifting the split reflectors, the focused acoustic beams were separated. As a result, the beam width in the focal region could be increased. Both numerical models of wave propagation using a k-wave approach and hydrophone measurements showed similar pressure waveforms at the focus and the distributions along and transverse to the lithotripter axis. The increase of the shifting distance from 0 mm to 7 mm resulted in the increase of -6 dB beam width from 7.1 mm to 13.9 mm and location of tensile peak on axis moving from z = -14 mm to 1 mm. The Lithotripters at 10 kV (intact reflector) and at 12 kV with the split reflectors shifted by 5 mm were compared with each other because of their similar peak positive pressures at the focus (8.07 MPa ± 0.05 MPa vs. 7.90 MPa ± 0.11 MPa, respectively). However, there were significant differences in their positive beam width (8.7 mm vs. 10.2 mm), peak negative pressure (-6.34 MPa ± 0.04 MPa vs. -7.13 MPa ± 0.13 MPa), the maximum tensile stress (7.55 MPa vs. 8.95 MPa) and shear stress (6.1 MPa vs. 7.76 MPa) in a 10-mm diameter spherical stone and bubble collapse time (127.6 μs ± 5.4 μs vs. 212.7 μs ± 8.2 μs). As a result, stone fragmentation efficiency was enhanced about 1.8-fold (57.9% ± 4.6% vs. 32.2% ± 5.6%, p < 0.05) when shifting the split reflectors. These results suggest that this new reflector design could change the characteristics of the lithotripter field and increase stone fragmentation efficiency.

Assessing the Magnitude of Effect of Bone Structures on Shockwave Lithotripsy Fragmentation: Results from an In Vitro Study

INTRODUCTION

Several anatomic and clinical factors have been implicated in the failure rates of shock wave lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model that incorporates the lumbar spine, including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteral stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate.

MATERIALS AND METHODS

An ordnance gelatin (OG) model was conceptualized and created to allow a pig's lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 g (1.2-cm diameter) were prepared using BegoStone plaster. The trial was divided into two arms: group 1 models had OG only and served as the control and group 2 models had the bone embedded in the gelatin with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the STORZ MODULITH SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2- and 4-mm filters, and the fragmentation coefficients (FC) were calculated. The Mann-Whitney test was used to compare FC between the two groups.

RESULTS

The mean fragmentation rate of group 1 was statistically significantly higher compared with group 2 using a 4-mm sieve (43% vs 0.62%, p < 0.001) and the 2-mm filter (18% vs 0.52%, p < 0.001).

CONCLUSIONS

The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an OG in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.

Optimal Skin-to-Stone Distance Is a Positive Predictor for Successful Outcomes in Upper Ureter Calculi following Extracorporeal Shock Wave Lithotripsy: A Bayesian Model Averaging Approach

Objectives

To investigate whether skin-to-stone distance (SSD), which remains controversial in patients with ureter stones, can be a predicting factor for one session success following extracorporeal shock wave lithotripsy (ESWL) in patients with upper ureter stones.

Patients and Methods

We retrospectively reviewed the medical records of 1,519 patients who underwent their first ESWL between January 2005 and December 2013. Among these patients, 492 had upper ureter stones that measured 4–20 mm and were eligible for our analyses. Maximal stone length, mean stone density (HU), and SSD were determined on pretreatment non-contrast computed tomography (NCCT). For subgroup analyses, patients were divided into four groups. Group 1 consisted of patients with SSD<25^th percentile, group 2 consisted of patients with SSD in the 25^th to 50^th percentile, group 3 patients had SSD in the 50^th to 75^th percentile, and group 4 patients had SSD≥75^th percentile.

Results

In analyses of group 2 patients versus others, there were no statistical differences in mean age, stone length and density. However, the one session success rate in group 2 was higher than other groups (77.9% vs. 67.0%; P = 0.032). The multivariate logistic regression model revealed that shorter stone length, lower stone density, and the group 2 SSD were positive predictors for successful outcomes in ESWL. Using the Bayesian model-averaging approach, longer stone length, lower stone density, and group 2 SSD can be also positive predictors for successful outcomes following ESWL.

Conclusions

Our data indicate that a group 2 SSD of approximately 10 cm is a positive predictor for success following ESWL.

Arguments for choosing extracorporeal shockwave lithotripsy for removal of urinary tract stones

At a time when there is an almost unlimited enthusiasm and preference among urologists for endoscopic stone removal, we have found it essential to meet some of the frequently presented arguments on why extracorporeal shockwave lithotripsy (SWL) should not be used. We have based our considerations in this brief article on our 30-35 years' experience with the non-invasive or least invasive technique that SWL represents. Stone disintegration, requirement of repeated treatment sessions, the concern of residual fragments, complications and economic aspects are some points that are discussed.