Intraoperative computed tomography for detection of residual stones in endourology procedures: systematic review and meta-analysis

BACKGROUND

Success rates in endourological procedures, notably percutaneous nephrolithotomy (PCNL) and ureteroscopy (URS), have demonstrated suboptimal outcomes, leading to more reinterventions and radiation exposure. Recently, the use of intraoperative computed tomography (ICT) scans has been hypothesized as a promising solution for improving outcomes in endourology procedures. With this considered, we conducted a comprehensive systematic review and meta-analysis encompassing all available studies that evaluate the impact of the use of intraoperative CT scans on surgical outcomes compared to conventional fluoroscopic-guided procedures.

METHODS

This systematic review was conducted in accordance with PRISMA guidelines. Multiple databases were systematically searched up to December of 2023. This study aimed to directly compare the use of an ICT scan with the standard non-ICT-guided procedure. The primary endpoint of interest was success rate, and the secondary endpoints were complications and reintervention rates, while radiation exposure was also evaluated. Data extraction and quality assessment were performed following Cochrane recommendations. Data was presented as an Odds ratio with 95%CI across trials and a random-effects model was selected for pooling of data.

RESULTS

A comprehensive search yielded 533 studies, resulting in the selection of 3 cohorts including 327 patients (103 ICT vs 224 in non-ICT). Primary outcome was significantly higher in the experimental group versus the control group (84.5% vs 41.4% respectively, 307 patients; 95% CI [3.61, 12.72]; p<0.00001; I2=0). Reintervention rates also decreased from 32.6% in the control to 12.6% in the ICT group (OR 0.34; 95%CI [0.12,0.94]; p =0.04; I2= 48%), whereas complication rates did not exhibit significant differences. Radiation exposure was also significantly reduced in two of the included studies.

CONCLUSION

This meta-analysis highlights a favorable outcome with intraoperative CT scan use in PCNL procedures, showing a considerable increase in SFR when compared to standard fluoroscopy and nephroscopy. Despite limited studies, our synthesis underscores the potential of ICT scans to significantly reduce residual stones and their consequences for endourology patients, as reinterventions and follow-up ionizing radiation studies.

Can shear wave elastography predict the success of shock‑wave lithotripsy used in renal stones treatment? A prospective study

OBJECTIVE

To evaluate the usage of shear wave elastography (SWE) in the prediction of the success rate of shock‑wave lithotripsy (SWL) treatment of renal stones.

PATIENTS AND METHODS

In the present study, SWL was performed for 100 patients presented with renal stones in the duration from May 2022 to August 2023. The patients were divided into 2 groups SWL responders and non-responders. The study compared between the 2 groups in terms of baseline parameters of the patients as age, sex, body mass index (BMI), stone size, stone location, stone density (HU), skin-to-stone distance (SSD), the degree of hydronephrosis and the stone elastography values.

RESULTS

There was no statistically significant relation between stone-free rate and degree of obstruction (p = 0.628), stone size (p = 0.390) upper calyceal location (p = 0.17), middle calyceal location (p = 0.66), and renal pelvis location (p = 1.0). Nevertheless, a statistically significant relation was found as regards lower calyceal location, stone density (HU), and stone Elastography values using multivariate analysis.

CONCLUSIONS

Measurement of stone density by shear wave elastography (SWE) can be used as an alternative to HU in decision-making before SWL. SWL success depends mainly on stone site, HU, and SWE values.

Identification of kidney stones in KUB X-ray images using VGG16 empowered with explainable artificial intelligence

A kidney stone is a solid formation that can lead to kidney failure, severe pain, and reduced quality of life from urinary system blockages. While medical experts can interpret kidney-ureter-bladder (KUB) X-ray images, specific images pose challenges for human detection, requiring significant analysis time. Consequently, developing a detection system becomes crucial for accurately classifying KUB X-ray images. This article applies a transfer learning (TL) model with a pre-trained VGG16 empowered with explainable artificial intelligence (XAI) to establish a system that takes KUB X-ray images and accurately categorizes them as kidney stones or normal cases. The findings demonstrate that the model achieves a testing accuracy of 97.41% in identifying kidney stones or normal KUB X-rays in the dataset used. VGG16 model delivers highly accurate predictions but lacks fairness and explainability in their decision-making process. This study incorporates the Layer-Wise Relevance Propagation (LRP) technique, an explainable artificial intelligence (XAI) technique, to enhance the transparency and effectiveness of the model to address this concern. The XAI technique, specifically LRP, increases the model's fairness and transparency, facilitating human comprehension of the predictions. Consequently, XAI can play an important role in assisting doctors with the accurate identification of kidney stones, thereby facilitating the execution of effective treatment strategies.

Ureteral wall thickness as a predictor for non-invasive treatment success for steinstrasse. Can we save time?

PURPOSE

We aimed to define factors affecting the non-invasive overall treatment success (medical expulsive therapy (MET) ± shock wave lithotripsy (SWL)) for uncomplicated ureteral steinstrasse (SS) clearance.

METHODS

We retrospectively evaluated consecutive patients who underwent SWL for renal stones between 2017 and 2021. Patients with uncomplicated SS were included. All patient's demographic and radiological data, e.g., age, gender, pre-SWL stenting, SS site, type, leading stone size in widest diameter (< 10 mm and ≥ 10 mm), ureteral wall thickness (UWT) in mm against the leading stone were collected. If SS was diagnosed, medical treatment was given for 4 weeks. In case of MET failure, either SWL for the leading stones + MET or direct URS was done. Non-invasive treatment success (SFR) was considered if complete clearance of SS occurred with no complications or the need for invasive intervention.

RESULTS

A total of 145 patients were included with mean age of 45.9 ± 12.4 years. SFR in case of MET only occurred in 27.9%. Complications happened in 26 patients (17.9%). Non-invasive treatment SFR was achieved in 78 patients (53.8%) totally where SS type I, leading stone size ≤ 10 mm type and decreased UWT around the leading stone increased treatment success.

CONCLUSION

Ureteral wall thickness is an important factor predicting SS management success. Besides the decreased UWT, non-invasive management should be offered for type I SS with leading stone ≤ 10 mm.

Kidney collecting system anatomy applied to endourology - a narrative review

OBJECTIVE

To evaluate the surgical anatomy of the kidney collecting system through a narrative review of the literature, highlighting its importance during diagnosis and its approach during surgical procedures for the treatment of renal stones.

MATERIAL AND METHODS

We carried out a review about the anatomy of the kidney collecting system. We analyzed papers published in the past 40 years in the databases Pubmed, Embase and Scielo, and we included only papers in English and excluded case reports, editorials and opinions of specialists.

RESULTS

Renal collecting system could be divided in four groups: A1 - kidney midzone (KM), drained by minor calyx that are dependent on the superior or the inferior caliceal groups; A2 - KM drained by crossed calyx, one draining into the superior caliceal group and another draining into the inferior caliceal group; B1 - KM drained by a major caliceal group independent of both the superior and inferior groups; and B2 - KM drained by minor calyx entering directly into the renal pelvis. Some details and anatomic variations of the collecting system are related to clinical and radiological aspects, particularly perpendicular calyces, interpyelocalyx space, position of calyces in relation to renal border, classification of the renal collecting system, infundibular diameter and the angle between the lower infundibulum and renal pelvis.

CONCLUSION

The knowledge of intra-renal collecting system divisions and variations as the angle between the renal pelvis and lower infundibula, position of the calices in relationship with renal edge and the diameter and position of the calyces are important for the planning of minimally invasive renal surgeries.

[Imaging in nephroureterolithasis]

In the acute diagnostics of a suspected nephroureterolithiasis, ultrasonography should be the examination modality of choice. In cases of suspected urolithiasis, unclear flank pain with fever or in cases of a solitary kidney, a noncontrast computed tomography (CT) scan should always subsequently be performed. If the sonography findings are inconclusive in pregnant women a magnetic resonance imaging (MRI) examination can be considered. If there are indications for urinary diversion, a retrograde imaging study should be performed as part of the urinary diversion. This or CT imaging is also suitable for preinterventional imaging before shock wave lithotripsy, percutaneous nephrolithotomy or ureteroscopy. Postinterventional imaging is not always necessary and sonography is often sufficient. In a conservative treatment approach an abdominal plain X‑ray can be used for follow-up assessment.

Three-Dimensional Virtual Reconstruction Method versus Standard Fluoroscopy as a Guiding Tool for an Optimal Puncture Rout in Patients Undergoing Percutaneous Nephrolithotomy: A Randomized Trial Study

PURPOSE

Three-Dimensional (3D) could help for planning and creating an optimal access route in percutaneous nephrolithotomy (PCNL) procedure by achieving a more accurate approach to the renal collecting system and stone treatment while decreasing the risk of complications. The aim of our study is to compare the efficacy of 3D imaging technique with standard fluoroscopy method as a guiding tool for renal stone location while striving to reduce intra-operative X-ray exposure in the former method.

MATERIALS AND METHODS

This randomised clinical trial enrolled 48 PCNL candidates who were referred to Sina Hospital (Tehran, Iran). Participants were divided into two equal groups of intervention (3D virtual reconstruction) and control, using block randomization method. Age, sex, stone type and location, X-ray exposure during the procedure, stone access accuracy rate and the necessity of blood transfusion during surgery were taken into account.

RESULTS

The Mean age of participants (n = 48) was 46.4 ± 4.8 years, 34 (70.8%) were male, 27 (56.3%) had partial staghorn stones and all participants had stones within the lower calyx. The radiation exposure time, stone access time and stone size were 2.99 ± 1.81 seconds, 272.3 ± 108.9 seconds and 23.06 ± 2.28 mm, respectively. In the intervention group, the accuracy rate for lower calyceal stone access was 91.5%. Also, X-ray exposure and time to stone access were significantly lower in the intervention group compared to the controls (P < 0.001).

CONCLUSION

We concluded that the utilization of 3D technology in the pre-operative location of renal calculi in PCNL candidates may result in a significant improvement in the accuracy and time to access the renal calculi, as well as reduction in X-ray exposure.

Efficient and Accurate Computed Tomography-Based Stone Volume Determination: Development of an Automated Artificial Intelligence Algorithm

PURPOSE

Given the shortcomings of current stone burden characterization (maximum diameter or ellipsoid formulas), we sought to investigate the diagnostic accuracy and precision of a University of California, Irvine-developed artificial intelligence (AI) algorithm for determining stone volume determination.

MATERIALS AND METHODS

A total of 322 noncontrast CT scans were retrospectively obtained from patients with a diagnosis of urolithiasis. The largest stone in each noncontrast CT scan was designated the "index stone." The 3D volume of the index stone using 3D Slicer technology was determined by a validated reviewer; this was considered the "ground truth" volume. The AI-calculated index stone volume was subsequently compared with ground truth volume as well with the scalene, prolate, and oblate ellipsoid formulas estimated volumes.

RESULTS

There was a nearly perfect correlation between the AI-determined volume and the ground truth (R=0.98). While the AI algorithm was efficient for determining the stone volume for all sizes, its accuracy improved with larger stone size. Moreover, the AI stone volume produced an excellent 3D pixel overlap with the ground truth (Dice score=0.90). In comparison, the ellipsoid formula-based volumes performed less well (R range: 0.79-0.82) than the AI algorithm; for the ellipsoid formulas, the accuracy decreased as the stone size increased (mean overestimation: 27%-89%). Lastly, for all stone sizes, the maximum linear stone measurement had the poorest correlation with the ground truth (R range: 0.41-0.82).

CONCLUSIONS

The University of California, Irvine AI algorithm is an accurate, precise, and time-efficient tool for determining stone volume. Expanding the clinical availability of this program could enable urologists to establish better guidelines for both the metabolic and surgical management of their urolithiasis patients.

Is supine a preferred position for percutaneous nephrolithotomy in the pediatric age group? A randomized controlled study

BACKGROUND

The aim is to evaluate supine versus prone position in mini-percutaneous nephrolithotomy in pediatric renal urolithiasis management.

METHODS

A randomized controlled trial was constructed to evaluate supine versus prone position in pediatric PCNL. Seventy pediatric patients with a stone burden ≥1.5 cm were randomized into two groups.

RESULTS

Sixty-three patients were available for evaluation in our study with no significant difference in the perioperative demographic data. The supine group showed a shorter operation time of 43.9 min compared to 73.5 min in the prone group. The stone-free rate was higher in the supine group, with a 93.9% SFR compared to 83.3% in the prone group. The supine group showed a shorter hospital stay of 2.0±1.0 days, compared to 3.20±1.56 days in the prone group. No significant difference was seen in the perioperative complication rate and fluoroscopy time between both groups.

CONCLUSIONS

Supine mini-percutaneous nephrolithotomy is safe and effective in managing pediatric renal stones, with a higher stone-free rate, less operative time, and less hospital stay compared to the prone position.

Percutaneous nephrolithotomy guided by 5G-powered robot-assisted teleultrasound diagnosis system: first clinical experience with a novel tele-assistance approach (IDEAL stage 1)

BACKGROUND

To demonstrate the technical feasibility of percutaneous nephrolithotomy (PCNL) guided by 5G-powered robot-assisted teleultrasound diagnosis system (RTDS) in a complex kidney-stone (CKS) cohort and present our preliminary outcomes. PCNL is highly skill-required, which hinders it popularization in primary medical units of remote regions. We designed an innovative tele-assistance approach to make PCNL easy to be operated by inexperienced surgeons.

METHODS

This was a prospective proof-of-concept study (IDEAL phase 1) on intraoperative tele-assistance provided by online urological experts via a 5G-powered RTDS. Total 15 CKS patients accepted this technology. Online experts manipulated a simulated probe to assist unskilled local operators by driving a patient-side robot-probe to guide and monitor the steps of access establishment and finding residual stones.

RESULTS

Median total delay was 177ms despite one-way network-connecting distance > 5,800 km. No perceptible delay of audio-visual communication, driving robot-arm or dynamic ultrasound images was fed back. Successful tele-assistance was obtained in all cases. The first-puncture access-success rate was 78.6% with a one-session SF rate of 71.3% and without complications of grade III-V.

CONCLUSIONS

The current technology based on 5G-powered RTDS can provide high-quality intraoperative tele-assistance, which has preliminarily shown satisfactory outcomes and reliable safety. It will break down a personal competence-based barrier to endow PCNL with more popular utilization.

TRIAL REGISTRATION

The study was approved by ethics committee of the Xinjiang Kezhou People's Hospital and ethics committee of the First Affiliated Hospital of Nanjing Medical University and was registered on http://www.chictr.org.cn (ChiCTR2200065849, 16/11/2022).

Endoscopic combined intrarenal surgery composed of micro-perc and retrograde intrarenal surgery in the treatment of complex kidney stones in children

OBJECTIVE

This research aims to explore the efficiency and safety of endoscopic combined intrarenal surgery (Micro-ECIRS) composed of micro-percutaneous nephrolithotomy (Micro-perc) and retrograde intrarenal surgery (RIRS) in the Galdakao-modified supine Valdivia (GMSV) position for a single session for the treatment of complex nephrolithiasis in children.

MATERIALS AND METHODS

This study retrospectively reviewed patients aged < 18 years who underwent Micro-ECIRS in the GMSV position for renal stones larger than 2 cm under ultrasound guidance between August 2020 to May 2022 at our institution.

RESULTS

A total of 13 patients (8 males and 5 females) received Micro-ECIRS for renal stones under ultrasound guidancewhile adopting the GMSV position. The average stone size was 2.7 cm (range: 2.1-3.7 cm). Among them, 6 patients had left kidney stones, 5 patients had right kidney stones, and 2 patients had bilateral kidney stones. The mean operative time was 70.5 min (range: 54-93 min). The mean hospital stay was 6.4 days (range: 4-9 days). The mean hemoglobin decrease was 8.2 g/L (range: 5.1-12.4 g/L). The total number of kidneys that had complete stone clearance was 8 kidneys at 48 h postoperatively, 11 kidneys at 2 weeks postoperatively, and 14 kidneys at 1 month postoperatively.

CONCLUSION

Our results demonstrate that Micro-ECIRS while patients are in the GMSV position is a safe and effective method for the treatment of complex children nephrolithiasis. However, all children made three hospital visits and received anesthesia three times. Further research is needed to confirm these findings.

Predicting stone composition via machine-learning models trained on intra-operative endoscopic digital images

OBJECTIVES

The aim of this study was to use deep learning (DL) of intraoperative images of urinary stones to predict the composition of urinary stones. In this way, the laser frequency and intensity can be adjusted in real time to reduce operation time and surgical trauma.

MATERIALS AND METHODS

A total of 490 patients who underwent holmium laser surgery during the two-year period from March 2021 to March 2023 and had stone analysis results were collected by the stone laboratory. A total of 1658 intraoperative stone images were obtained. The eight stone categories with the highest number of stones were selected by sorting. Single component stones include calcium oxalate monohydrate (W1), calcium oxalate dihydrate (W2), magnesium ammonium phosphate hexahydrate, apatite carbonate (CH) and anhydrous uric acid (U). Mixed stones include W2 + U, W1 + W2 and W1 + CH. All stones have intraoperative videos. More than 20 intraoperative high-resolution images of the stones, including the surface and core of the stones, were available for each patient via FFmpeg command screenshots. The deep convolutional neural network (CNN) ResNet-101 (ResNet, Microsoft) was applied to each image as a multiclass classification model.

RESULTS

The composition prediction rates for each component were as follows: calcium oxalate monohydrate 99% (n = 142), calcium oxalate dihydrate 100% (n = 29), apatite carbonate 100% (n = 131), anhydrous uric acid 98% (n = 57), W1 + W2 100% (n = 82), W1 + CH 100% ( n = 20) and W2 + U 100% (n = 24). The overall weighted recall of the cellular neural network component analysis for the entire cohort was 99%.

CONCLUSION

This preliminary study suggests that DL is a promising method for identifying urinary stone components from intraoperative endoscopic images. Compared to intraoperative identification of stone components by the human eye, DL can discriminate single and mixed stone components more accurately and quickly. At the same time, based on the training of stone images in vitro, it is closer to the clinical application of stone images in vivo. This technology can be used to identify the composition of stones in real time and to adjust the frequency and energy intensity of the holmium laser in time. The prediction of stone composition can significantly shorten the operation time, improve the efficiency of stone surgery and prevent the risk of postoperative infection.

Single Specialty-Operated Renal Stone Removal: Initial Experience from 3 Interventional Radiology Centers

This retrospective analysis of the feasibility and safety of percutaneous renal stone removal using single-use flexible ureteroscopes was conducted at 3 academic centers. Twelve patients (58% men) underwent 14 percutaneous renal stone removal procedures between December 2021 and March 2023. All patients experienced symptom improvement and resolution of obstruction after stone removal. The procedural success rate was 92%. Only 1 patient required an additional stone removal procedure. No major adverse events occurred during or after the procedures. The percutaneous nephrostomy removal rate was 92%, with a median tube removal time of 5 weeks. The median procedural and pulsed fluoroscopy times were 106.5 and 16.3 minutes, respectively. Preliminary findings demonstrated that percutaneous renal stone removal using single-use endoscopes by interventional radiologists is feasible and safe.

Do pseudoxanthoma elasticum patients have higher prevalence of kidney stones on computed tomography compared to hospital controls?

BACKGROUND

Pseudoxanthoma elasticum (PXE) is an autosomal recessive disease characterized by diminished inorganic plasma pyrophosphate (PPi), a strong calcification inhibitor. In addition to more typical calcification of skin, retina and arterial wall a diminished plasma PPi could lead to other ectopic calcification, such as formation of kidney stones.

OBJECTIVE

To compare the prevalence of kidney stones between PXE patients and hospital controls on computed tomography (CT).

METHOD

Low-dose CT images of PXE patients and controls were assessed by one radiologist, who was blinded for the diagnosis PXE. The number of kidney stones, and the size of the largest stone was recorded. Odds ratios (ORs) for having kidney stone were calculated using multivariable adjusted logistic regression.

RESULTS

Our study comprised 273 PXE patients and 125 controls. The mean age of PXE patients was 51.5 ± 15.9 years compared to 54.9 ± 14.2 in the control group (p = 0.04) and PXE patients more often were women (63 vs. 50%, p = 0.013). The prevalence of kidney stones on CT was similar: 6.9% in PXE patients, compared to 5.6% in controls (p = 0.6). In the multivariate analysis adjusting for age and sex, there was no significantly higher odds for PXE patients on having stones, compared to controls: OR 1.48 (95% CI 0.62-3.96).

CONCLUSION

There is no significant difference in the prevalence of incidental kidney stones on CT in PXE patients versus controls.

Deep-learned generation of renal dual-energy CT from a single-energy scan

AIM

To investigate the role of the deep-learning (DL) method in the generation of dual-energy computed tomography (DECT) images from single-energy images for precise diagnosis of kidney stone type.

MATERIALS AND METHODS

DECT of 23 patients was acquired, and the stone types were investigated based on the DECT software suggestions. The data were divided into two paired groups:120 kVp input and 80 kVp target and 120 kVp input and 135 kVp targets, p2p-UNet-GAN was exploited to generate the different energy images based on the common CT protocols.

RESULTS

The images generated of the generative adversarial network (GAN) network were evaluated based on the SSIM, PSNR, and MSE metrics, and the values were estimated as 0.85-0.95, 28-32, and 0.85-0.89 respectively. The attenuation ratio of test patient images were estimated and compared with real patient reports. The network achieved high accuracy in stone region localisation and resulted in accurate stone type predictions.

CONCLUSION

This study presents a useful method based on the DL technique to reduce patient radiation dose and facilitate the prediction of urinary stone types using single-energy CT imaging.

Has fluoroless endourology (URS and PCNL) come of age? Evidence from a comprehensive literature review

INTRODUCTION

Radiation via the use of imaging is a key tool in management of kidney stones. Simple measures are largely taken by the endourologists to implement the 'As Low As Reasonably Achievable' (ALARA) principle, including the use of fluoroless technique. We performed a scoping literature review to investigate the success and safety of fluoroless ureteroscopy (URS) or percutaneous nephrolithotomy (PCNL) procedures for the treatment of KSD.

METHODS

A literature review was performed searching bibliographic databases PubMed, EMBASE and Cochrane library, and 14 full papers were included in the review in accordance with the PRISMA guidelines.

RESULTS

Of the 2535 total procedures analysed, 823 were fluoroless URS vs. 556 fluoroscopic URS; and 734 fluoroless PCNL vs. 277 fluoroscopic PCNL. The SFR for fluoroless vs. fluoroscopic guided URS was 85.3% and 77%, respectively (p=0.2), while for fluoroless PCNL vs. fluoroscopic group was 83.8% and 84.6%, respectively (p=0.9). The overall Clavien-Dindo I/II and III/IV complications for fluoroless and fluoroscopic guided procedures were 3.1% (n=71) and 8.5% (n=131), and 1.7% (n=23) and 3% (n=47) respectively. Only 5 studies reported a failure of the fluoroscopic approach with a total of 30 (1.3%) failed procedures.

CONCLUSION

The ALARA protocol has been implemented in endourology in numerous ways to protect both patients and healthcare workers during recent years. Fluoroless procedures for treatment of KSD are safe and effective with outcomes comparable to standard procedures and could become the new frontier of endourology in selected cases.

Longitudinal follow-up of incidental renal calculi on computed tomography

RATIONALE AND OBJECTIVES

Measuring small kidney stones on CT is a time-consuming task often neglected. Volumetric assessment provides a better measure of size than linear dimensions. Our objective is to analyze the growth rate and prognosis of incidental kidney stones in asymptomatic patients on CT.

MATERIALS AND METHODS

This retrospective study included 4266 scans from 2030 asymptomatic patients who underwent two or more nonenhanced CT scans for colorectal screening between 2004 and 2016. The DL software identified and measured the volume, location, and attenuation of 883 stones. The corresponding scans were manually evaluated, and patients without follow-up were excluded. At each follow-up, the stones were categorized as new, growing, persistent, or resolved. Stone size (volume and diameter), attenuation, and location were correlated with the outcome and growth rates of the stones.

RESULTS

The stone cohort comprised 407 scans from 189 (M: 124, F: 65, median age: 55.4 years) patients. The median number of stones per scan was 1 (IQR: [1, 2]). The median stone volume was 17.1 mm3 (IQR: [7.4, 43.6]) and the median peak attenuation was 308 HU (IQR: [204, 532]. The 189 initial scans contained 291stones; 91 (31.3%) resolved, 142 (48.8%) grew, and 58 (19.9) remained persistent at the first follow-up. At the second follow-up (for 27 patients with 2 follow-ups), 14/44 (31.8%) stones had resolved, 19/44 (43.2%) grew and 11/44 (25%) were persistent. The median growth rate of growing stones was 3.3 mm3/year, IQR: [1.4,7.4]. Size and attenuation had a moderate correlation (Spearman rho 0.53, P < .001 for volume, and 0.50 P < .001 for peak attenuation) with the growth rate. Growing and persistent stones had significantly greater maximum axial diameter (2.7 vs 2.3 mm, P =.047) and peak attenuation (300 vs 258 HU, P =.031) CONCLUSION: We report a 12.7% prevalence of incidental kidney stones in asymptomatic adults, of which about half grew during follow-up with a median growth rate of about 3.3 mm3/year.

Models to predict the surgical outcome of mini-ECIRS (endoscopic combined intrarenal surgery) for renal and/or ureteral stones

To establish a safer and more efficient treatment strategy with mini-endoscopic combined intrarenal surgery (ECIRS), the present study aimed to develop models to predict the outcomes of mini-ECIRS in patients with renal and/or ureteral stones. We retrospectively analysed consecutive patients with renal and/or ureteral stones who underwent mini-ECIRS at three Japanese tertiary institutions. Final treatment outcome was evaluated by CT imaging at 1 month postoperatively and stone free (SF) was defined as completely no residual stone or residual stone fragments ≤ 2 mm. Three prognostic models (multiple logistic regression, classification tree analysis, and machine learning-based random forest) were developed to predict surgical outcomes using preoperative clinical factors. Clinical data from 1432 ECIRS were pooled from a database registered at three institutions, and 996 single sessions of mini-ECIRS were analysed in this study. The overall SF rate was 62.3%. The multiple logistic regression model consisted of stone burden (P < 0.001), number of involved calyces (P < 0.001), nephrostomy prior to mini-ECIRS (P = 0.091), and ECOG-PS (P = 0.110), wherein the area under the curve (AUC) was 70.7%. The classification tree analysis consisted of the number of involved calyces with an AUC of 61.7%. The random forest model showed that the top predictive variable was the number of calyces involved, with an AUC of 91.9%. Internal validation revealed that the AUCs for the multiple logistic regression model, classification tree analysis and random forest models were 70.4, 69.6 and 85.9%, respectively. The number of involved calyces, and a smaller stone burden implied a SF outcome. The machine learning-based model showed remarkably high accuracy and may be a promising tool for physicians and patients to obtain proper consent, avoid inefficient surgery, and decide preoperatively on the most efficient treatment strategies, including staged mini-ECIRS.

Retained foreign body post-PCNL: an unusual complication and endoscopic management

During this era of advanced and minimally invasive procedures for treating urolithiasis, percutaneous nephrolithotomy (PCNL) remains the primary choice for removing large renal calculi. While there are various known complications associated with PCNL, such as bleeding, sepsis and injury to neighboring organs, the occurrence of retained foreign bodies as a result of the procedure is rarely reported. In this case report, we present a unique instance of encrustation involving a retained guidewire sheath following PCNL, which was initially mistaken for a residual stone fragment in imaging studies. Fortunately, the foreign body was successfully removed using retrograde intrarenal surgery.

Application of image overlapping in percutaneous nephrolithotomy

OBJECTIVE

To investigate the application of ultrasound and CT image overlap in percutaneous nephrolithotomy (PCNL).

METHODS

A total of 140 patients with complicated kidney stones requiring PCNL were prospectively enrolled, from January 2020 to December 2022. These patients were randomly divided into 2 groups, with 70 patients each in the research group and the control group. All participants underwent dual-source, non-contrast CT scan of both kidneys and pelvis before surgery. Preoperative three-dimensional CT reconstruction and simulated puncture were performed in patients from the research group. The best puncture path was determined through ultrasound and CT image overlap. Puncture guided by regular CT and ultrasound was conducted in patients from the control group. Differences in the surgical outcomes between the two groups were compared.

RESULTS

Compared to the control group, the research group had higher stone clearance rate in stage I PCNL, success rate of one-time puncture, less percutaneous channels, less reduction of hemoglobin and shorter procedure time. Complications in stage I PCNL were comparable in the two groups, and there was no significant change in the final stone clearance rates between the two groups.

CONCLUSION

An optimal puncture channel can be chosen using ultrasound and CT image overlap. PCNL can be achieved with precise puncturing, thus achieving coincidence between imaging and anatomy and reducing the amount of blood loss during stage I of PCNL. It also shortens the procedure time and improves stone clearance rate of PCNL.

Renal Imaging in Stone Disease: Which Modality to Choose?

Numerous imaging modalities are available to the provider when diagnosing or surveilling kidney stones. The decision to order one over the other can be nuanced and especially confusing to non-urologic practitioners. This manuscript reviews the main modalities used to image stones in the modern era - renal bladder ultrasound, Kidney Ureter Bladder plain film radiography (KUB), magnetic resonance imaging (MRI), and non-contrast computerized tomography (NCCT). While NCCT has become the most popular and familiar modality for most practitioners, particularly in the acute setting, ultrasound is a cost-effective technology that is adept at monitoring interval stone development in patients and evaluating for the presence of hydronephrosis. KUB and MRI also occupy unique niches in the management of urolithiasis. In the correct clinical setting, each of these modalities has a role in the acute workup and management of suspected nephrolithiasis.

[Safety and efficiency of retrograde intrarenal surgery without X-ray guidance]

INTRODUCTION

The main stages of flexible ureteroscopy in patients with renal stones are usually performed under X-ray guidance. Long-term exposure of ionizing radiation can have negative effects on the patients with nephrolithiasis and the operating team.

AIM

To study the results of retrograde intrarenal surgery (RIRS) without fluoroscopic guidance.

MATERIALS AND METHODS

The results of flexible ureteroscopy (fURS) without X-ray-guidance in 76 patients were analyzed. There were 46 (53.3%) men and 30 (46.7%) women. The average age was 50.4+/-14.6 years. All patients underwent laboratory tests and non-contrast-enhanced computed tomography to determine the size and density of the stone. In all cases, preoperative ureteral stenting was performed. The average stone size was 10.5+/-4.2 mm. First, ureteroscopy with a rigid endoscope was done to assess the ureter and determine the depth of the introducing ureteral access sheath. After removing the ureteroscope along the guidewire, a ureteral access sheath was put at this distance. An inspection of the collecting system and laser fragmentation of kidney stones were performed using a flexible ureteroscope. In 64 (84.2%) patients, a 4.7 Ch stent was put at the end of the procedure, while in the remaining 12 (15.8%) patients, a ureteral catheter was left for 1-2 days. The operation time, stone-free rate, and the number of intra- and postoperative complications were studied.

RESULTS

All fURS were successful and performed without X-ray guidance. The average operation time was 42.5+/-8.0 minutes. After the first session, stone-free rate was 92.1% (70/76). In 6 (7.9%) cases, residual stones were found, which were completely removed after the second session. Intraoperative complications, namely perforation of the upper calyx by the distal end of the ureteral access sheath, were observed in 2 (2.6%) patients, which did not require any additional interventions. Postoperative complications occurred in 10 (13.2%) patients, including fever in 6 (7.9%) and hematuria in 4 (5.3%) cases. There were no serious complications, such as ureteral perforation or sepsis, and no blood transfusion was performed.

CONCLUSION

Flexible ureteroscopy with laser lithotripsy can be performed safely and effectively without X-ray guidance.

Initial experience with robot-assisted ureteroscopy with Ily® Robot

The aim of this study is to present the first Italian experience with robotic-assisted retrograde intrarenal surgery (rRIRS) using the Ily® platform. Procedures were performed for renal stones using the Ily® Robot (STERLAB, Vallauris, France), which is a ureteroscope holder with multiple degrees of freedom that can be controlled remotely through a wireless controller. In March 2023, consecutive patients with indications for rRIRS were included in the study. Demographic variables and stone characteristics were collected, and standard perioperative data were assessed. The one-month stone-free rate (SFR, i.e. no residual fragments) was evaluated using ultrasound. All participating surgeons filled out a Surgeons' Satisfaction Questionnaire (SSQ) based on a Likert-type scale. The questionnaire focused on: 1) ease of use; 2) ergonomics during renal cavity exploration; 3) stability during stone fragmentation. Among the patients, one had bilateral stones, while two had stones on the right side. The mean stone size was 13 mm. The average operative time was 70 minutes and the mean docking time was three minutes. No perioperative complications were recorded, and all patients were discharged on the first postoperative day. The one-month SFR was 100%. The SSQ scores were as follows: 1) ease of use: 4/5; 2) ergonomics: 5/5; 3) stability during stone fragmentation: 5/5. Based on the initial experience, the results indicate the feasibility, safety, and effectiveness of rRIRS. The ergonomic efficiency of the system was highly appreciated by the surgeons. While a cost-effectiveness analysis within clinical trials is necessary, rRIRS shows the potential for a more sustainable future for endoscopists and an improved workplace environment.

Fluoroscopy Is Essential in Retrograde Intrarenal Surgery

Objective

This study aimed to investigate the necessity of using fluoroscopy in retrograde intrarenal surgery (RIRS). Material and Methods. A total of 612 patients who underwent RIRS for kidney stones were evaluated and divided into two groups. Group 1 routinely underwent the operation with fluoroscopy due to opaque stones (n: 504). In group 2, the procedure was performed without fluoroscopy because of nonopaque stones (n: 108). Both groups were assessed for stone size, location, and number. Success and complication rates were compared between the two groups.

Conclusion

This study was designed with the thought of not using fluoroscopy in RIRS patients with nonopaque stones and having the same stone-free rates in opaque stones. In the statistical analysis, there was no difference between the groups with and without scope for stone side, size, localization, and number; likewise, the complication rates developed in the comparison of both groups, stone-free rates, and hospital stay were the same. Discussion. Advances in the calibration of instruments, the development of optical systems, and improvements in imaging system resolution have gradually reduced the need for fluoroscopy in RIRS. This study provides further evidence that fluoroscopy is unnecessary in RIRS procedures, thereby eliminating unnecessary radiation exposure.

What is the safe and effective dilator number during access in PCNL? Three-shot dilation versus classical sequential Amplatz dilation

BACKGROUND

Although PCNL has been used for a long time to treat nephrolithiasis, there is still contradictory information concerning the use of the dilation method. In this study, we aimed to compare conventional sequential Amplatz dilatation (SAD) using ten dilators and a method using three dilators (12, 20, and 30 Fr), which we named "three-shot dilatation" (3SD), in terms of fluoroscopy time (FT), operation time, bleeding and stone-free rates.

METHODS

The study included patients who underwent PCNL with the SAD and 3SD methods. A different surgeon with extensive endourology experience applied each technique. One of the surgeons operated on the patients using the SAD method with ten dilators, and the other surgeon performed the operations using the 3SD method involving three Amplatz dilators (12, 20, and 30 Fr).

RESULTS

A total of 283 patients, 138 in the 3SD group and 145 in the SAD group, were included in the study. The mean age of the patients was 47.32 ± 13.71 years. There was no statistically significant difference between the two groups regarding preoperative characteristics (p > 0.05). The FTs of access 2, total access, and total operation were significantly shorter in the 3SD group (p = 0.0001). The decrease in hemoglobin was statistically significant in the 3SD group compared to the SAD group (p = 0.022), while the blood transfusion requirements of the groups were similar (p = 0.176). There was no statistically significant difference between the two groups regarding stone-free rates (p = 0.973). In four patients in the SAD group, re-access was necessary due to the loss of passage due to the guide wire slipping out of its place.

CONCLUSION

Intraoperative FT can be shortened using the described 3SD method without compromising surgical safety. However, this method can be used as an intermediate step in the transition to one-shot dilation by surgeons experienced in performing SAD.

Evaluation of the safety and efficiency of color Doppler ultrasound-guided percutaneous nephrolithotomy in clinical practice: results from a retrospective study

This study evaluated the clinical value of color Doppler ultrasound-guided percutaneous nephrolithotomy (PCNL) in avoiding bleeding caused by punctured blood vessels. Herein, we retrospectively included patients who underwent color Doppler ultrasound-guided PCNL or PCNL using the conventional channel technique from August 2018 to August 2022. The clinical characteristics of patients during surgery, complications, and hospital stay were recorded and compared. Overall, 228 patients were enrolled, with 126 patients (age, 47.6 ± 13.2 years; men: 57.14%) in the color Doppler ultrasound-guided PCNL group and 102 patients (age, 46.6 ± 12.3 years) in the B-mode ultrasound-guided puncture group. The total operation time (63.5 ± 15.5 vs. 61.3 ± 16.3 min, p = .5236) and stone clearance rate (86.50% vs. 83.33%, p = .7139) were similar between the two groups. However, the puncture time for the color Doppler ultrasound-guided PCNL group was longer than that for the B-mode ultrasound-guided puncture group (5.1 ± 2.3 vs. 2.6 ± 1.6 min, p = .0019). Moreover, the length of postoperative hospital stay in the color Doppler ultrasound-guided PCNL group reduced significantly by ∼1 day compared with that in the B-mode ultrasound-guided puncture group (4.5 ± 1.6 vs. 5.6 ± 2.1 days, p = .0087). The blood transfusion rate (1.58% vs. 4.9%, p = .0399), sedation-related adverse event rate (0.79% vs. 2.9%, p = .0332), perineal hematoma incidence (0% vs. 2.94%, p < .0001), and serum decreased hemoglobin levels (12.2 ± 9.7 vs. 23.5 ± 10.1 g/L, p < .001) after color Doppler ultrasound-guided PCNL were significantly lower than those after B-mode ultrasound-guided puncture. The stone clearance rate was similar between the two groups, with a similar operation time. Moreover, color Doppler ultrasound-guided PCNL shortened the postoperative hospital stay and decreased Hb levels, blood transfusion rate, and perineal hematoma incidence.

Do Hounsfield Units have any significance in predicting intra- and postoperative outcomes in retrograde intrarenal surgery using Holmium and Thulium fiber laser? Results from the FLEXible ureteroscopy Outcomes Registry (FLEXOR)

PURPOSE

To evaluate outcomes of flexible ureteroscopy for renal stones by comparing hard versus soft stones based on their attenuation on computed tomography (Hounsfield Units-HU).

METHODS

Patients were divided into two groups according to the type of laser employed [Holmium:YAG (HL) or Thulium fiber laser (TFL)]. Residual fragments (RF) were defined as > 2 mm. Multivariable logistic regression analysis was performed to evaluate factors associated with RF and RF needing further intervention.

RESULTS

4208 patients from 20 centers were included. In whole series, age, recurrent stones, stone size, lower pole stones (LPS), and multiple stones were predictors of RF at multivariable analysis and LPS and stone size with RF requiring further treatment. HU and TFL were associated with lesser RF and RF requiring an additional treatment. In HU < 1000 stones, recurrent stones, stone size, and LPS were predictors of RF at multivariable analysis, whereas TFL was less likely associated with RF. Recurrent stones, stone size, and multiple stones were predictors of RF requiring further treatment, while LPS and TFL were associated with lesser RF requiring further treatment. In HU ≥ 1000 stones, age, stone size, multiple stones, and LPS were predictors of RF at multivariable analysis, while TFL was less likely associated with RF. Stone size and LPS were predictors of RF requiring further treatment, whereas TFL was associated with RF requiring further treatment.

CONCLUSION

Stone size, LPS, and use of HL are predictors of RF after RIRS for intrarenal stones regardless of stone density. HU should be considered an important parameter in predicting SFR.

Effective deep learning classification for kidney stone using axial computed tomography (CT) images

INTRODUCTION

Stone formation in the kidneys is a common disease, and the high rate of recurrence and morbidity of the disease worries all patients with kidney stones. There are many imaging options for diagnosing and managing kidney stone disease, and CT imaging is the preferred method.

OBJECTIVES

Radiologists need to manually analyse large numbers of CT slices to diagnose kidney stones, and this process is laborious and time-consuming. This study used deep automated learning (DL) algorithms to analyse kidney stones. The primary purpose of this study is to classify kidney stones accurately from CT scans using deep learning algorithms.

METHODS

The Inception-V3 model was selected as a reference in this study. Pre-trained with other CNN architectures were applied to a recorded dataset of abdominal CT scans of patients with kidney stones labelled by a radiologist. The minibatch size has been modified to 7, and the initial learning rate was 0.0085.

RESULTS

The performance of the eight models has been analysed with 8209 CT images recorded at the hospital for the first time. The training and test phases were processed with limited authentic recorded CT images. The outcome result of the test shows that the Inception-V3 model has a test accuracy of 98.52 % using CT images in detecting kidney stones.

CONCLUSIONS

The observation is that the Inception-V3 model is successful in detecting kidney stones of small size. The performance of the Inception-V3 Model is at a high level and can be used for clinical applications. The research helps the radiologist identify kidney stones with less computational cost and disregards the need for many experts for such applications.

Comparison of endoscopic versus CT assessment of stone-free status after percutaneous nephrolithotomy (PCNL)

This study is aimed to determine whether postoperative low dose computed tomography (LDCT) imaging is necessary after percutaneous nephrolithotomy (PCNL), or the surgeon's intraoperative assessment of residual fragments (RF) is sufficient and avoidance of postoperative imaging with reduction of radiation exposure can be achieved. Data of all 610 patients who underwent PCNL in prone position in our institution from February 2009 to September 2020 was collected. Parameters such as age, gender, BMI, ASA-Classification, stone related parameters and the surgeon's assessment of stone-free status were analyzed. The LDCT performed postoperatively was compared to the intraoperative assessment of the surgeon regarding RF. The mean age of patients was 52.82 years; the mean BMI was 28.18 kg/m2. In 418 cases, the surgeon made a clear statement about the presence of RF and postoperative LDCT was carried out. The discrepancy between the two methods (surgeon´s assessment vs. LDCT) was significant at p < 0.0001. The sensitivity, specificity, positive and negative predictive value of the surgeon when assessing RF were 24.05%, 99.45%, 98.28% and 50%. Stone free rate (SFR) after primary PCNL was 45.57%. The overall SFR at discharge was 96.23%. Although the surgeon´s assessment of RF was reliable, postoperative LDCT imaging should still be performed if endoscopic stone clearance is suspected due to the high false negative rate and the low negative predictive value. The optimal timing of postoperative imaging following PCNL remains unclear.

Interdisciplinary planning improves radiologist obtained access for percutaneous nephrolithotomy

INTRODUCTION

Proper antegrade access for percutaneous nephrolithotomy (PCNL) is essential for success but can be challenging. Previous work evaluating access obtained by interventional radiology (IR), largely in the emergent setting, has shown high rates of additional access at the time of PCNL. We hypothesize that efforts to improve pre-procedural communication between urology and IR can impact the utility of the access for subsequent PCNL.

MATERIAL AND METHODS

We conducted a retrospective review of patients undergoing PCNL at a single hospital from January 2011 to December 2022. Adult patients undergoing PCNL with established preoperative access were included.

RESULTS

A total of 141 cases were identified with preoperative access. A total of 111 patients had evidence of planning with IR prior to antegrade access. There were high rates of anatomic abnormality (50%) and staghorn calculus (53%). Patients with planned access had higher body mass index (BMI). While preoperative access was initially utilized in 97% of cases, 6% required additional access to be obtained intraoperatively; this included a low rate of new access in those that were previously discussed with IR (4% vs. 17%, p = 0.02). Overall stone free rates (91%), rates of second stage procedures (55%) and complications (14%) were similar between planned and unplanned groups.

CONCLUSION

In this retrospective study of complex patients with large stone burden presenting for PCNL with preoperative antegrade access obtained by IR, the rate of new access was far lower than prior reports. This was likely influenced by urologist involvement in planning access.

Development and external validation of a machine learning-based model to classify uric acid stones in patients with kidney stones of Hounsfield units < 800

The correct diagnosis of uric acid (UA) stones has important clinical implications since patients with a high risk of perioperative morbidity may be spared surgical intervention and be offered alkalization therapy. We developed and validated a machine learning (ML)-based model to identify stones on computed tomography (CT) images and simultaneously classify UA stones from non-UA stones. An international, multicenter study was performed on 202 patients who received percutaneous nephrolithotomy for kidney stones with HU < 800. Data from 156 (77.2%) patients were used for model development, while data from 46 (22.8%) patients from a multinational institution were used for external validation. A total of 21,074 kidney and stone contour-annotated CT images were trained with the ResNet-18 Mask R-convolutional neural network algorithm. Finally, this model was concatenated with demographic and clinical data as a fully connected layer for stone classification. Our model was 100% sensitive in detecting kidney stones in each patient, and the delineation of kidney and stone contours was precise within clinically acceptable ranges. The development model provided an accuracy of 99.9%, with 100.0% sensitivity and 98.9% specificity, in distinguishing UA from non-UA stones. On external validation, the model performed with an accuracy of 97.1%, with 89.4% sensitivity and 98.6% specificity. SHAP plots revealed stone density, diabetes mellitus, and urinary pH as the most important features for classification. Our ML-based model accurately identified and delineated kidney stones and classified UA stones from non-UA stones with the highest predictive accuracy reported to date. Our model can be reliably used to select candidates for an earlier-directed alkalization therapy.

Endourological management of ureteric stump syndrome

A man in his 50s presented with right flank pain and intermittent haematuria for 15 days. He was evaluated and diagnosed to have bilateral staghorn renal calculi with left poorly functioning kidney. He underwent right kidney stone clearance followed by laparoscopic left simple nephrectomy. Postoperatively, he developed recurrent urinary tract infections. On evaluation, non-contrast CT of the abdomen revealed calculus in left ureteral stump and he was diagnosed to have ureteric stump syndrome. He underwent ureteroscopy which revealed multiple stump calculi and complete stone clearance was achieved. Currently, the patient is asymptomatic and doing well after a follow-up of 1 year.

A multicenter study on the application of artificial intelligence radiological characteristics to predict prognosis after percutaneous nephrolithotomy

Background

A model to predict preoperative outcomes after percutaneous nephrolithotomy (PCNL) with renal staghorn stones is developed to be an essential preoperative consultation tool.

Objective

In this study, we constructed a predictive model for one-time stone clearance after PCNL for renal staghorn calculi, so as to predict the stone clearance rate of patients in one operation, and provide a reference direction for patients and clinicians.

Methods

According to the 175 patients with renal staghorn stones undergoing PCNL at two centers, preoperative/postoperative variables were collected. After identifying characteristic variables using PCA analysis to avoid overfitting. A predictive model was developed for preoperative outcomes after PCNL in patients with renal staghorn stones. In addition, we repeatedly cross-validated their model's predictive efficacy and clinical application using data from two different centers.

Results

The study included 175 patients from two centers treated with PCNL. We used a training set and an external validation set. Radionics characteristics, deep migration learning, clinical characteristics, and DTL+Rad-signature were successfully constructed using machine learning based on patients' pre/postoperative imaging characteristics and clinical variables using minimum absolute shrinkage and selection operator algorithms. In this study, DTL-Rad signal was found to be the outstanding predictor of stone clearance in patients with renal deer antler-like stones treated by PCNL. The DTL+Rad signature showed good discriminatory ability in both the training and external validation groups with AUC values of 0.871 (95% CI, 0.800-0.942) and 0.744 (95% CI, 0.617-0.871). The decision curve demonstrated the radiographic model's clinical utility and illustrated specificities of 0.935 and 0.806, respectively.

Conclusion

We found a prediction model combining imaging characteristics, neural networks, and clinical characteristics can be used as an effective preoperative prediction method.

Ultrasound-guided percutaneous nephrolithotomy (PCNL) success rates in patients with elevated body mass index: a comparative study

Percutaneous nephrolithotomy (PCNL) is considered gold standard treatment of renal stones larger than 20 mm. Several studies have shown that ultrasound guidance during this procedure is more effective and safer than fluoroscopy. A higher body mass index (BMI) can make ultrasound-guided renal access more difficult and unsuccessful. We present a prospective analysis and comparison of ultrasound-guided PCNL in patients with normal and increased body mass index. We performed a prospective comparison of patients who underwent ultrasound-guided PCNL to remove renal stones by a single surgeon between 2020 and 2022. Patients with BMIs greater than 30 (mean 33.87-obese) were compared to those with BMIs less than 30 (mean 25.69-non-obese). Demographic, perioperative, and follow-up data were collected, analyzed, and included in this study. Total of 98 consecutive patients, with 49 patients in each group were analyzed. No statistically significant differences were observed in terms of stone volume (P = 0.085), stone density (P = 0.5590), location of renal access (P = 0.108), surgery duration (P = 0.38), blood loss (P = 0.54), or laboratory changes after surgery (P = 0.60). 87.76% of obese patients were stone free per CT scan at follow-up, compared to 73.47% of normal-weight patients (P = 0.1238). According to Clavien-Dindo classification, six patients in the non-obese group experienced grade II (10%) and grade III (2%) complications, as opposed to six patients in the obese group with grade I (2%), grade II (6%), and grade III (2%) complications. There was no significant correlation between body mass index and the success or safety of ultrasound-guided PCNL. Although more challenging, a higher BMI should not be an impediment to performing this approach. This method is safe, with no increased incidence of postoperative complications or compromise in stone-free status postoperatively and can diminish or avoid both patient's and medical team's exposure to ionizing radiation.

Dual-energy CT kidney stone characterization-can diagnostic accuracy be achieved at low radiation dose?

OBJECTIVES

To assess the accuracy of low-dose dual-energy computed tomography (DECT) to differentiate uric acid from non-uric acid kidney stones in two generations of dual-source DECT with stone composition analysis as the reference standard.

METHODS

Patients who received a low-dose unenhanced DECT for the detection or follow-up of urolithiasis and stone extraction with stone composition analysis between January 2020 and January 2022 were retrospectively included. Collected stones were characterized using X-ray diffraction. Size, volume, CT attenuation, and stone characterization were assessed using DECT post-processing software. Characterization as uric acid or non-uric acid stones was compared to stone composition analysis as the reference standard. Sensitivity, specificity, and accuracy of stone classification were computed. Dose length product (DLP) and effective dose served as radiation dose estimates.

RESULTS

A total of 227 stones in 203 patients were analyzed. Stone composition analysis identified 15 uric acid and 212 non-uric acid stones. Mean size and volume were 4.7 mm × 2.8 mm and 114 mm3, respectively. CT attenuation of uric acid stones was significantly lower as compared to non-uric acid stones (p < 0.001). Two hundred twenty-five of 227 kidney stones were correctly classified by DECT. Pooled sensitivity, specificity, and accuracy were 1.0 (95%CI: 0.97, 1.00), 0.93 (95%CI: 0.68, 1.00), and 0.99 (95%CI: 0.97, 1.00), respectively. Eighty-two of 84 stones with a diameter of  ≤ 3 mm were correctly classified. Mean DLP was 162 ± 57 mGy*cm and effective dose was 2.43 ± 0.86 mSv.

CONCLUSIONS

Low-dose dual-source DECT demonstrated high accuracy to discriminate uric acid from non-uric acid stones even at small stone sizes.

KEY POINTS

• Two hundred twenty-five of 227 stones were correctly classified as uric acid vs. non-uric acid stones by low-dose dual-energy CT with stone composition analysis as the reference standard. • Pooled sensitivity, specificity, and accuracy for stone characterization were 1.0, 0.93, and 0.99, respectively. • Low-dose dual-energy CT for stone characterization was feasible in the majority of small stones  < 3 mm.

[Mini-PCNL, micro-PCNL or RIRS: comparative efficacy and safety in renal stones up to 2 cm]

INTRODUCTION

One of the main trends in the evolution of endoscopic treatment of urolithiasis is the miniaturization of instruments. This is obvious in the development of minimally invasive percutaneous nephro-lithotomy (PCNL) and retrograde intrarenal surgery (RIRS). However, there are few studies comparing the efficiency and safety of these methods.

AIM

To evaluate and compare the efficiency and safety of mini-PCNL, micro-PCNL and RIRS in the treatment of kidney stones up to 2 cm in size.

MATERIALS AND METHODS

Between October 2020 and December 2022, a total 72 patients underwent minimally invasive endoscopic procedures in two centers, including RIRS (n=30), mini-PCNL (n=26) and micro-PCNL (n=16) using thulium fiber laser FiberLase U2. The efficiency of procedure (stone free rate [SFR]) was assessed using non-contrast-enhanced CT. SFR was considered as the absence of residual fragments > 4 mm. Complications (safety) were evaluated based on the Clavien-Dindo classification.

RESULTS

The mean age of all patients was 47.7 (22-84) years. There were no significant differences between three groups in stone characteristics according to CT (maximum diameter, density, volume and number of stones, the presence of pelvicalyceal dilation). SFR was significantly different between the groups (p=0.034). The overall SFR was 81.9% (n=59). After RIRS, mini-PCNL, and micro-PCNL the SFR was 93.3%, 80.8%, and 62.5%, respectively. A significant difference was found between the RIRS and micro-PNL groups, with 2 out of 30 and 6 out of 16 patients requiring repeat procedure, respectively (p=0.026). The overall rate of complication of grades I-II, IIIa and IIIb according to Clavien-Dindo was 6.9%, 9.7% and 6.9%, respectively. A significant difference was found between the RIRS and micro-PCNL (p=0.021) for grade I-II complications. A rate of grade III complications was not differed between the groups. The operation time was higher for mini-PNL (79.8 (30-145) min), and it was shorter for RIRS (55.7 (30-155) min). The length of stay was lower in RIRS group (4.5 (1-12) days).

CONCLUSION

The highest SFR was achieved in the RIRS group. In terms of the number of complications of I-II grades according to Clavien-Dindo, the duration of the procedure and the length of stay, RIRS also showed the advantage. There were no significant differences in efficiency and safety between the micro-PNL and mini-PNL. There are not enough studies comparing minimally invasive methods for treating kidney stones. It is necessary to continue research in this area in order to develop an optimal algorithm for choosing the method of endoscopic treatment.

Real-world Practice Stone-free Rates After Ureteroscopy: Variation and Outcomes in a Surgical Collaborative

BACKGROUND

Studies assessing the stone-free rate (SFR) after ureteroscopy are limited to expert centers with varied definitions of stone free. Real-world data including community practices related to surgeon characteristics and outcomes are lacking.

OBJECTIVE

To evaluate the SFR for ureteroscopy and its predictors across diverse surgeons in Michigan.

DESIGN, SETTING, AND PARTICIPANTS

We assessed the Michigan Urological Surgery Improvement Collaborative (MUSIC) clinical registry for patients with renal or ureteral stones treated with ureteroscopy between 2016 and 2021 who had postoperative imaging.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Stone free was defined as no fragments on imaging reports within 60 d entered by independent data abstractors. Factors associated with being stone free were examined using logistic regression, including annual surgeon volume. We then assessed variation in surgeon-level SFRs adjusted for risk factors.

RESULTS AND LIMITATIONS

We identified 6487 ureteroscopies from 164 surgeons who treated 2091 (32.2%) renal and 4396 (67.8%) ureteral stones. The overall SFRs were 49.6% (renal) and 72.7% (ureteral). Increasing stone size, lower pole, proximal ureteral location, and multiplicity were associated with not being stone free. Female gender, positive urine culture, use of ureteral access sheath, and postoperative stenting were associated with residual fragments when treating ureteral stones. Adjusted surgeon-level SFRs varied for renal (26.1-72.4%; p < 0.001) and ureteral stones (52.2-90.2%; p < 0.001). Surgeon volume was not a predictor of being stone free for renal stones. Limitations include the lack of imaging in all patients and use of different imaging modalities.

CONCLUSIONS

The real-world complete SFR after ureteroscopy is suboptimal with substantial surgeon-level variation. Interventions focused on surgical technique refinement are needed to improve outcomes for patients undergoing ureteroscopy and stone intervention.

PATIENT SUMMARY

Results from a diverse group of community practicing and academic center urologists show that for a large number of patients, it is not possible to be completely stone free after ureteroscopy. There is substantial variation in surgeon outcomes. Quality improvement efforts are needed to address this.

Combined semirigid and flexible ureterorenoscopy for the treatment of large renal stones

Ureteroscopy is recognized as a minimally invasive and readily accessible method with low morbidity, favorable outcomes, and rapid post-interventional recovery. Recent advancements in rigid and flexible ureteroscopes have enhanced their efficiency, durability, and capability to accommodate accessory instruments. In this retrospective analysis, we evaluated 75 consecutive patients with large renal stones (stone burden between 2 and 4 cm) treated using a combination of semirigid and flexible ureteroscopy between January 1, 2020, and December 31, 2021. Stone properties and anatomical information were collected from the image archives derived from computed tomography (CT) and/or KUD radiography. Multiple ureteroscopy sessions were required for bigger stones. The length of the hospital stay, operation time, stone-free rate, preoperative and postoperative complications, and complication rates were examined. The average age of the patients was 52.7 years, with a mean stone burden of 31.45 mm. Most stones were in the renal pelvis, followed by the upper calyx. The average operative time was 56.2 minutes. After the initial ureteroscopy session, the stone clearance rate was 76%, which increased to 92% after two ureteroscopy sessions. Complication rates were evaluated using the Clavien-Dindo modified system, with an overall complication rate of 18.4%. Most of the complications were Clavien Grades I and II, with no grade V complication encountered. Large renal stones can be treated by combining semirigid and flexible ureteroscopy to reduce the operative time and protect the flexible ureteroscope.

A Novel Computed Tomography-Ultrasound Image Fusion Technique for Guiding the Percutaneous Kidney Access

PURPOSE

To describe the feasibility of computed tomography (CT)-ultrasound image fusion technique on guiding percutaneous kidney access in vitro and vivo.

MATERIALS AND METHODS

we compare CT-ultrasound image fusion technique and ultrasound for percutaneous kidney puncture guidance by using an in vitro pig kidney model. The fusion method, fusion time, ultrasound screening time, and success rate of puncture were compared between the groups. Next, patients with kidney stones in our hospital were randomized in the study of simulated puncture guidance. The general condition of patients, fusion method, fusion time, and ultrasound screening time were compared between the groups.

RESULTS

A total of 45 pig models were established, including 23 in the CT-ultrasound group and 22 in the ultrasound group. The ultrasound screening time in the CT-ultrasound group was significantly shorter than that in the ultrasound group (P < .001). In addition, the success rate of puncture in the CT-ultrasound group was significantly higher than that in the ultrasound group (P =.015). Furthermore, in the simulated PCNL puncture study, baseline data including age, BMI, and S.T.O.N.E score between the two groups showed no statistical difference. The ultrasound screening time of the two groups was (2.60 ± 0.33) min and (3.37 ± 0.51) min respectively, and the difference was statistically significant (P < .001).

CONCLUSION

Our research revealed that the CT-ultrasound image fusion technique was a feasible and safe method to guide PCNL puncture. Compared with traditional ultrasound guidance, the CT-ultrasound image fusion technique can shorten the learning curve of PCNL puncture, improve the success rate of puncture, and shorten the ultrasound screening time.

Retrograde intrarenal surgery for stones associated with renal anomalies: caliceal diverticulum, horseshoe kidney, medullary sponge kidney, megacalycosis, pelvic kidney, uretero-pelvic junction obstruction

PURPOSE OF REVIEW

Nowadays, due to the increase of imaging diagnosis, we identify easily renal anomalies, and we can choose between a wide range of armamentarium to treat symptomatic stones in those challenging cases. However, there is a lack of evidence and consensus on its use. The aim of this narrative review is to collect all the available data about safety and efficacity of retrograde intrarenal surgery (RIRS) in the treatment of kidney stones associated to a renal anomaly.

RECENT FINDINGS

Renal anomalies are uncommon findings and even more if it has to be associated with renal stones. After a literature review of the past 2 years, there are a small number of studies that compare the outcomes in patients who have been treated with minimally invasive modalities and they are mainly focus on RIRS.

SUMMARY

It is of extreme importance to know the advances on the stone treatment in anomalous kidneys. With the development of new laser technologies, RIRS is becoming a more interesting technique with high success rate and safety. Further studies are needed to make an accurate statement about the adequate surgical technique for each renal anomaly and also, clinical trials using new laser technologies.

Percutaneous management of caliceal diverticula: a narrative review

PURPOSE OF REVIEW

Caliceal diverticula are relatively uncommon within urologic practice and may be difficult to diagnose and treat. We aim to highlight contemporary studies examining surgical interventions for patients with caliceal diverticula, with a focus on percutaneous intervention, and provide updated practical recommendations for the management of these patients.

RECENT FINDINGS

Studies within the last 3 years examining surgical treatment options for caliceal diverticular calculi are limited. When flexible ureteroscopy (f-URS) and percutaneous nephrolithotomy (PCNL) are examined within the same observational cohorts, PCNL is associated with improved stone-free rates (SFRs), lower requirement for re-intervention, and longer lengths of stay (LOS). Retrograde f-URS for the treatment of caliceal diverticula and diverticular calculi is associated with satisfactory safety and efficacy outcomes. There are no studies in the last 3 years that provide supporting evidence to use shock wave lithotripsy to treat caliceal diverticular calculi.

SUMMARY

Recent studies examining surgical interventions for patients with caliceal diverticula are limited to small observational studies. Heterogeneity in LOS and follow-up protocol limits comparisons between series. Despite technological advancements in f-URS, PCNL appears to be associated with more favorable and definitive outcomes. PCNL continues to be the preferred treatment strategy for patients with symptomatic caliceal diverticula when deemed technically feasible.

Ultrasound-Only Percutaneous Nephrolithotomy Is Safe and Effective Compared to Fluoroscopy-Directed Percutaneous Nephrolithotomy

Introduction: Outcomes after ultrasound-only percutaneous nephrolithotomy (PCNL), in which no fluoroscopy is used, are not well known. The goal of this study was to compare outcomes of ultrasound-only and fluoroscopy-directed PCNL. Materials and Methods: Prospectively collected data from the Registry for Stones of the Kidney and Ureter database were reviewed for all patients who underwent PCNL at one academic center from 2015 to 2021. Primary outcomes were complications and stone-free rates (no residual fragments ≥3 mm). Results: Of the 141 patients who underwent ultrasound-only PCNL and 147 who underwent fluoroscopy-directed PCNL, there was no difference in complication rates (15% vs 16%, p = 0.87) or stone-free status (71% vs 65%, p = 0.72), respectively. After adjusting for body mass index, American Society of Anesthesiologists (ASA), stone size, and stone complexity by Guy score, ultrasound-only PCNL was not associated with any increased odds of complications (odds ratio [OR] 0.7, 95% confidence interval [CI] 0.3-1.6, p = 0.41) or residual stone fragments ≥3 mm (OR 1.0, 95% CI 0.5-1.9, p = 0.972) compared with fluoroscopy-directed PCNL. Ultrasound-only PCNL was associated with shorter operative time (median 99.5 vs 126 minutes, p < 0.001), and the use of ultrasound remained a significant predictor of short operative time (<100 minutes) after controlling for supine positioning, stone size, and stone complexity by Guy score (OR 2.31, 95% CI 1.01-5.29, p = 0.048). Patients in the ultrasound-only group were spared a mean radiation exposure dose of 10 mGy per procedure. Conclusions: Ultrasound-only PCNL is safe and achieves similar stone-free rates compared with fluoroscopy-directed PCNL with the added benefit of avoidance of radiation.

Identification of Clinically Insignificant Renal Calculi on Sonography

OBJECTIVE

To determine factors predicting if a radiologists... report of a .. stone... on ultrasound (US) was not actually a clinically significant stone, based on subsequent computed tomogram (CT). US often overestimates stone size and various pathologic entities are also hyperechoic;.ßthus, a subsequent CT without a clinically significant stone may represent unnecessary radiation exposure. A decision-tree and nomogram were developed to predict when stones are unlikely on subsequent CT.

METHODS

Retrospective analysis of patients, of any age, receiving CT within 24.ßhours of a sonographic report documenting a single renal stone, during 2019...2020, in any phase of care, at one institution. Novel stone-likelihood-systems for US and CT (US-SLS, CT-SLS) were devised and validated to classify stones as clinically significant or insignificant, with CT as the gold standard. Binomial logistic regression predicting clinically significant stones was performed with sonographic and patient characteristics.

RESULTS

Eight hundred twenty patients had US followed by CT, 228 (27.8%) reported documented stones, 140 (17.1%) reported a single stone. Clinically significant stones were associated with larger stone size (P: .002), location (P: .002), hydronephrosis (P: .04), shadowing-artifact (P: .02) depth.ßto.ßstone (P: .008), and Body mass Index (BMI) (P: .01). US-SLS had higher sensitivity (95.4%) and negative-predictive-value (81.8%) compared to a multivariate model of significant variables.

CONCLUSION

US-SLS appears to exclude clinically irrelevant .. stones... better than established criteria including twinkle or shadow in this retrospective analysis. A diagnostic algorithm and nomogram are presented. US-SLS and the associated decision tree can assist providers in avoiding unnecessary radiation when clinically significant stones are unlikely.

Enhancing sizing accuracy in ultrasound images with an alternative ADMIRE model and dynamic range considerations

Ultrasound imaging can struggle with sizing accuracy, especially when the targets have a significantly different amplitude compared to the surrounding background. In this work, we consider the challenging task of accurately sizing hyperechoic structures, and specifically kidney stones, where accurate sizing is critical for determining medical intervention. AD-Ex, an extended alternative model of our aperture domain model image reconstruction (ADMIRE) pre-processing method, is introduced and is designed to improve clutter removal and improve sizing accuracy. We compare this method against other resolution enhancing methods such as minimum variance (MV) and generalized coherence factor (GCF), and against those methods using AD-Ex as a pre-processing tool. These methods are evaluated among patients with kidney stone disease, with the task of accurately sizing the stones against the gold standard, computed tomography (CT). Stone ROI's were selected using contour maps as reference from which the lateral stone size was estimated. Among the in vivo kidney stone cases we processed, AD-Ex+MV had the overall lowest sizing error among the methods, with an average error of 10.8% compared to the next best method AD-Ex which had an average error of 23.4%. For reference, DAS had an average error of 82.4%. Though dynamic range was evaluated to determine optimal thresholding for sizing applications, variability between stone cases was too high for any conclusions to be drawn at this time.

[Not Available]

Kidney stone disease is rapidly increasing with a strong relationship to metabolic syndrome. This review gives a brief overview of the current state and current treatment modalities. Increasing use of CT and ultrasound scans leads to increased diagnosis of asymptomatic kidney stones, which rarely require treatment. The trend in stone treatment goes towards endoscopic lithotripsy which together with ESWL enables a personalised approach. Obstructive stones with infection require urgent intervention to reduce mortality. Increased fluid intake, dietary changes as well as potassium citrate supplements are the most important elements in stone prevention in the common idiopathic stone disease.

In Vivo Prediction of Kidney Stone Fragility Using Radiomics-Based Regression Models

Introduction: The surgical technique for urinary stone removal is partly influenced by its fragility, as prognosticated by the clinician. This feasibility study aims to develop a linear regression model from CT-based radiomic markers to predict kidney stone comminution time in vivo with two ultrasonic lithotrites. Materials and Methods: Patients identified by urologists at our institution as eligible candidates for percutaneous nephrolithotomy were prospectively enrolled. The active engagement time of the lithotrite in breaking the stone during surgery denoted the comminution time of each stone. The comminution rate was computed as the stone volume disintegrated per minute. Stones were grouped into three fragility classes (fragile, moderate, hard), based on inverse of the comminution rates with respect to the mean. Multivariable linear regression models were trained with radiomic features extracted from clinical CT images to predict comminution times in vivo. The model with the least root mean squared error (RMSE) on comminution times and the fewest misclassification of fragility was finally selected. Results: Twenty-eight patients with 31 stones in total were included in this study. Stones in the cohort averaged 1557 (±2472) mm3 in volume and 5.3 (±7.4) minutes in comminution time. Ten stones had nonmoderate fragility. Linear regression of stone volume alone predicted comminution time with an RMSE of 6.8 minutes and missed all 10 stones with nonmoderate fragility. A fragility model that included stone volume, internal morphology, shape-based radiomics, and device type improved RMSE to below 3.3 minutes and correctly classified 20/21 moderate and 6/10 nonmoderate stones. Conclusions: CT metrics-based fragility models may provide information to surgeons regarding kidney stone fragility and facilitate the selection of stone removal procedures.