Development and internal validation of a nomogram for predicting stone-free status after flexible ureteroscopy for renal stones

Comparative analysis of scoring systems for patients undergoing retrograde intrarenal surgery with isolated lower calyx stones

PURPOSE

It is critical to provide patients with accurate information on potential surgical outcomes during the preoperative phase. Several scoring systems have been developed for this specific purpose. This study aimed to examine the predicted efficacy of scoring systems in patients with isolated lower calyx stones who underwent retrograde intrarenal surgery (RIRS).

METHODS

We performed a retrospective analysis of 85 patients who underwent RIRS for lower calyx stones between 2016 and 2023. The study computed each participant's Resorlu-Unsal Stone score (RUSS), R.I.R.S. scoring system score, Modified Seoul National University Renal Stone Complexity (S-ReSC) score, S.T.O.N.E. score, Ito's nomogram, and T.O.HO score. Residual stones less than 4 mm were classified as clinically insignificant residual fragments (CIRFs) and regarded as successful. Following that, we used receiver-operating characteristic (ROC) curves to compare various scoring systems' success predictions.

RESULTS

The median scores for RUSS, R.I.R.S. scoring system, Modified S-ReSC, S.T.O.N.E., Ito's nomogram, and T.O.HO score were 1 (1), 7 (2), 2 (0), 11 (1), 18 (4), and 7 (1), respectively. When CIRF cases were included, the stone-free rate increased to 80%. Only Ito's nomogram from scoring systems has a statistically significant cut-off value for success in ROC analysis (p = 0.021). In multivariate analysis, stone volume and preoperative hydronephrosis were associated with success (p = 0.004 and p = 0.035, respectively).

CONCLUSION

In the multivariate analysis, none of the scoring systems were significantly associated with success. Hence, a new scoring system must be developed exclusively for patients with isolated lower pole stones undergoing RIRS.

Stone decision engine accurately predicts stone removal and treatment complications for shock wave lithotripsy and laser ureterorenoscopy patients

Kidney stones form when mineral salts crystallize in the urinary tract. While most stones exit the body in the urine stream, some can block the ureteropelvic junction or ureters, leading to severe lower back pain, blood in the urine, vomiting, and painful urination. Imaging technologies, such as X-rays or ureterorenoscopy (URS), are typically used to detect kidney stones. Subsequently, these stones are fragmented into smaller pieces using shock wave lithotripsy (SWL) or laser URS. Both treatments yield subtly different patient outcomes. To predict successful stone removal and complication outcomes, Artificial Neural Network models were trained on 15,126 SWL and 2,116 URS patient records. These records include patient metrics like Body Mass Index and age, as well as treatment outcomes obtained using various medical instruments and healthcare professionals. Due to the low number of outcome failures in the data (e.g., treatment complications), Nearest Neighbor and Synthetic Minority Oversampling Technique (SMOTE) models were implemented to improve prediction accuracies. To reduce noise in the predictions, ensemble modeling was employed. The average prediction accuracies based on Confusion Matrices for SWL stone removal and treatment complications were 84.8% and 95.0%, respectively, while those for URS were 89.0% and 92.2%, respectively. The average prediction accuracies for SWL based on Area-Under-the-Curve were 74.7% and 62.9%, respectively, while those for URS were 77.2% and 78.9%, respectively. Taken together, the approach yielded moderate to high accurate predictions, regardless of treatment or outcome. These models were incorporated into a Stone Decision Engine web application (http://peteranoble.com/webapps.html) that suggests the best interventions to healthcare providers based on individual patient metrics.

New infundibulopelvic angle measurement method can predict stone-free rates following retrograde intrarenal surgery

To enhance the accuracy of predicting stone-free rates after retrograde intrarenal surgery, we devised a novel approach to assess the renal infundibulopelvic angle. We conducted a retrospective review of patient records for those who underwent retrograde intrarenal surgery for renal stones between April 2018 and August 2019. Patient demographics, stone characteristics, and perioperative data were recorded. Subsequently, we introduced a modified angle measurement called the pelvic stone angle and evaluated its predictive performance for stone-free rates by comparing it with the traditional method in scoring systems. A total of 43 individuals were included in this study. Notable differences in stone burden and Hounsfield unit measurements were found between stone-free and non-stone-free patients. The pelvic stone angle demonstrated a good model fit when used in scoring systems, performing equally well as the conventional approach. The area under the receiver operating characteristic curve for the R.I.R.S. scoring system using the pelvic stone angle and the conventional approach did not show a significant difference. In conclusion, the predictive ability of the pelvic stone angle for stone-free rates was comparable to the old measurement method. Moreover, scoring systems using the pelvic stone angle exhibited a better model fit than those using the conventional approach.

A nomogram clinical prediction model for predicting urinary infection stones: development and validation in a retrospective study

PURPOSE

This study aimed to develop a nomogram prediction model to predict the exact probability of urinary infection stones before surgery in order to better deal with the clinical problems caused by infection stones and take effective treatment measures.

METHODS

We retrospectively collected the clinical data of 390 patients who were diagnosed with urinary calculi by imaging examination and underwent postoperative stone analysis between August 2018 and August 2023. The patients were randomly divided into training group (n = 312) and validation group (n = 78) using the "caret" R package. The clinical data of the patients were evaluated. Univariate and multivariate logistic regression analysis were used to screen out the independent influencing factors and construct a nomogram prediction model. The receiver operating characteristic curve (ROC), calibration curves, and decision curve analysis (DCA) and clinical impact curves were used to evaluate the discrimination, accuracy, and clinical application efficacy of the prediction model.

RESULTS

Gender, recurrence stones, blood uric acid value, urine pH, and urine bacterial culture (P < 0.05) were independent predictors of infection stones, and a nomogram prediction model ( https://zhaoyshenjh.shinyapps.io/DynNomInfectionStone/ ) was constructed using these five parameters. The area under the ROC curve of the training group was 0.901, 95% confidence interval (CI) (0.865-0.936), and the area under the ROC curve of the validation group was 0.960, 95% CI (0.921-0.998). The results of the calibration curve for the training group showed a mean absolute error of 0.015 and the Hosmer-Lemeshow test P > 0.05. DCA and clinical impact curves showed that when the threshold probability value of the model was between 0.01 and 0.85, it had the maximum net clinical benefit.

CONCLUSIONS

The nomogram developed in this study has good clinical predictive value and clinical application efficiency can help with risk assessment and decision-making for infection stones in diagnosing and treating urolithiasis.

Influence of tract location on the outcomes of endoscopic combined intrarenal surgery: A retrospective analysis of 1000 cases

OBJECTIVES

This study aimed to investigate the influence of tract location on surgical outcomes in endoscopic combined intrarenal surgery (ECIRS), considering the location of residual stones.

METHODS

From January 2015 to December 2021, 1417 consecutive patients underwent ECIRS in three hospitals. After excluding patients with preoperative percutaneous nephrostomy, intended multi-stage procedures, those with a tract in the renal pelvis, and those with multiple tracts, 1000 patients were retrospectively analysed by comparing three groups based on tract location: group 1 (upper calyx), group 2 (middle calyx), and group 3 (lower calyx). A multivariate logistic regression model was implemented to assess whether the tract location independently affected the stone-free status.

RESULTS

Patient characteristics were significantly different among the groups in terms of age, stone laterality, presence of calyceal stones, and hydronephrosis. There were no differences in stone-free rate (SFR) among the three groups. Multivariate analysis indicated that the tract location (group 1 or 2 compared with group 3) did not significantly affect the stone-free status (odds ratio = 1.4, 0.9-1.9, p = 0.066). Surgical duration significantly varied among the groups, with the shortest time observed in group 1. Organ injury was observed exclusively in group 1 (1.13%). Residual fragments were predominantly found in the lower calyx, with the calyx associated with the tract being the second most common location.

CONCLUSIONS

Tract location does not significantly affect SFR. To improve the SFR, observation of the lower calyx and tract placement is important.

Factors affecting the intraoperative calculi excretion during flexible ureteroscopy lithotripsy: an in vitro analysis

OBJECTIVE

To explore the parameters influencing intraoperative calculi excretion (ICE) during flexible ureteroscopy lithotripsy (fURL) using in vitro simulation experiments.

METHODS

3D-printed human kidney models were used to simulate the elimination of gravel during fURL. The factors influencing the ICE during fURL were analyzed by comparing the effects of different degrees of hydronephrosis (mild, moderate, and severe), surgical positions (supine and lateral position), ratios of endoscope-sheath diameter (RESD) (0.625, 0.725, and 0.825), gravel sizes (0.50-1.00 mm, 0.25-0.50 mm, and 0.10-0.25 mm), and ureteral access sheaths (UASs) (traditional UAS and negative-pressure UAS) on ICE.

RESULTS

The impacts of various UAS, RESD, degree of hydronephrosis, surgical positions, and gravel sizes on ICE were all significant (p < 0.05). We found no evidence of multicollinearity for all the independent variables, and the linear regression equation fitted as ICE ( g / min ) = 0.102 + 0.083 ∗ UAS grade - 0.050 ∗ RESD grade - 0.048 ∗ hydronephrosis grade + 0.065 ∗ position grade - 0.027 ∗ gravel size grade (R2 = 0.569).

CONCLUSION

Employing negative-pressure UAS, smaller RESD, milder hydronephrosis, lateral position, and smaller gravel size contribute to improved ICE during fURL. Among them, the adoption of negative-pressure UAS had the most substantial effects.

Retrograde Intrarenal Surgery for Renal Stones: Is It a Safe and Effective Option in Preschool Children?

INTRODUCTION

Few studies in the literature describe the Retrograde Intra-Renal Surgery (RIRS) outcome in preschool children. We evaluated the feasibility, stone-free rate and complications of RIRS in preschool children at two European tertiary care centres of Pediatric Urology.

MATERIAL AND METHODS

The retrospective study includes all children undergone RIRS for stones <25 mm from 2017 to 2022. Patients were divided into Group 1 <5 years (G1) and Group 2 >5 years (G2). Semirigid ureterorenoscope 4.5-6.5 Ch and a 7.5 Fr flexible ureteroscope with a 9.5/11 Ch ureteral access sheath (UAS) were used. Stone-free rate (SFR) was evaluated at 3 months. Fischer/Chi-square test for qualitative data and Mann-Whitney for quantitative data were used for statistical analysis.

RESULTS

63 patients underwent RIRS, 19 G1-patients, median age 3.55 ± 1.06 years (range 1.5-5 years), and 44 G2-patients, median age 11.25 ± 2.95 (range 6-17 years) (p < 0.00001). Intraoperative complications occurred in 1 case in G1(5%) and 3 in G2(7%) (p = 1): two minor ureteric injuries in G2 were treated by a prolonged JJ-stent. Postoperative fever was reported in 3 cases in G1 (16%) and 4 in G2(9%) (p = 0.42), while post-operative hematuria in 4 G1-patients (21%) and in 7 G2-patients (16%) (p = 0.72). SFR was 84.2% in G1 and 88.6% in G2. At an average follow-up of 15.05 ± 4.83 months in G1 and 19.95 ± 10.36 months in G2, reintervention for residual stones was necessary in 3 cases in G1(16%) and in 6 cases in G2(14%) (p = 1).

CONCLUSIONS

In a European country with low-volume pediatric stone centers, RIRS is a promising therapeutic option in young children as it offers acceptable stone-free rate and a low incidence of high-grade complications.

LEVEL OF EVIDENCE

III.

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.

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.

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.

Residual fragment size following retrograde intrarenal surgery: a critical evaluation of related variables

Given the limited data on the predictive factors of residual kidney stone size after flexible ureteroscopy (fURS), this study aims to investigate the variables affecting residual stone size. The medical records of 642 patients without complications being treated for kidney stones with fURS between July 2014 and May 2022 were reviewed retrospectively, and the information of the 170 patients in whom residual stones were found was recorded. In addition to patient-specific factors and stone characteristics, length of postoperative hospital stay, postoperative fever, and preoperative antiaggregant use were evaluated. Of the 170 patients ultimately included in the study. The mean age was 51.56 (± 14.70). The mean stone size was 14.01 mm (± 5.75), the mean residual stone size was 7.04 mm (± 2.51), and the mean stone density was 829 Hounsfield units (± 395.06). The mean infundibulopelvic angle (IPA) was 49.37º (± 15.37), and 41.2% of the stones were non-opaque. The mean parenchymal thickness was 22.88 mm (± 5.55). 34 patients were on antiaggregant therapy. Preoperative stone size increases in stone density and decreases in IPA were found to be correlated with increase residual stone size (p < 0.001, p < 0.001, and p < 0.001, respectively). In addition, larger residual stones were observed after the fURS procedure in patients using anticoagulants and those without hydronephrosis (p = 0.02 and p = 0.016, respectively). Use of reliable predictive factors to forecast residual stone size after fURS may help to inform those treated and enable urologists to design rational surgical strategies.

External validation of the current scoring systems and derivation of a novel scoring system to predict stone free rates after retrograde intrarenal surgery in patients with cumulative stone diameter of 2-4 cm

OBJECTIVE

Our primary aim is to perform the external validation of the current scoring systems in predicting stone-free status (SFS) after retrograde intrarenal surgery (RIRS) for renal stones 2-4 cm and develop a novel scoring system by re-examining possible predictive factors related to SFS.

METHODS

Patients who underwent RIRS due to renal stones with a cumulative stone diameter of 2-4 cm between January 2017 and March 2021 were retrospectively screened. Residual stones ≤2 mm were defined as clinically insignificant, and these cases were considered to have SFS. Possible predictive factors related to SFS were examined using the multivariate logistic regression analysis. A nomogram and a scoring system were developed using independent predictive variables. The prediction ability of the previous and the new scoring system were evaluated with the ROC analysis.

RESULTS

The existing scoring systems were found to be insufficient in predicting SFS (AUC < 0.660 for all). The independent predictors of SFS were identified as stone surface area (OR: 0.991, p < 0.001), stone density (OR: 0.998, p < 0.001), number of stones (OR: 0.365, p = 0.033), and stone localization (p = 0.037). Using these predictive markers, a new scoring system with a score ranging between 4 and 15 was developed. The AUC value for this scoring system was 0.802 (0.734-0.870).

CONCLUSION

The RUSS, S-ReSC and R.I.R.S. scoring systems and Ito's nomogram failed to predict SFS in stones >2 cm. The SFS predictive ability of our new scoring system was higher in >2 cm stones compared to the other scoring systems.

Impact of Preoperative Ureteral Stenting in Retrograde Intrarenal Surgery for Urolithiasis

Background and Objectives: Ureteral stent insertion passively dilates the ureter. Therefore, it is sometimes used preoperatively before flexible ureterorenoscopy to make the ureter more accessible and facilitate urolithiasis passage, especially when ureteroscopic access has failed or when the ureter is expected to be tight. However, it may cause stent-related discomfort and complications. This study aimed to assess the effect of ureteral stenting prior to retrograde intrarenal surgery (RIRS). Materials and Methods: Data from patients who underwent unilateral RIRS for renal stone with the use of a ureteral access sheath from January 2016 to May 2019 were retrospectively analyzed. Patient characteristics, including age, sex, BMI, presence of hydronephrosis, and treated side, were recorded. Stone characteristics in terms of maximal stone length, modified Seoul National University Renal Stone Complexity score, and stone composition were evaluated. Surgical outcomes, including operative time, complication rate, and stone-free rate, were compared between two groups divided by whether preoperative stenting was performed. Results: Of the 260 patients enrolled in this study, 106 patients had no preoperative stenting (stentless group), and 154 patients had stenting (stenting group). Patient characteristics except for the presence of hydronephrosis and stone composition were not statistically different between the two groups. In surgical outcomes, the stone-free rate was not statistically different between the two groups (p = 0.901); however, the operation time for the stenting group was longer than that of the stentless group (44.8 ± 24.2 vs. 36.1 ± 17.6 min; p = 0.001). There were no differences in the complication rate between the two groups (p = 0.523). Conclusions: Among surgical outcomes for RIRS with a ureteral access sheath, preoperative ureteral stenting does not provide a significant advantage over non-stenting with respect to the stone-free rate and complication rate.

Can additional variables be used to predict stone-free rates following retrograde intrarenal surgery? Anticoagulants and parenchyma thickness: a detailed examination

The purpose of this article is to identify the factors that predict the success of retrograde intrarenal surgery (RIRS), with a focus on the effect of renal parenchymal thickness and anticoagulant use on stone-free rates. From February 2014 to April 2022, cases of kidney stones treated with RIRS at our clinic were retrospectively screened. The study included 642 cases meeting all inclusion and exclusion criteria. The patients who were observed to be stone free after a single session of RIRS were assigned to Group F, while those with residual fragments were assigned to Group R. Group F comprised 472 patients, while Group R included 170 patients. The two groups have compared certain preoperative and postoperative laboratory and radiological parameters. The infundibulopelvic angle was significantly more acute in Group R (45.63 ± 16.25 vs. 49.28 ± 15.36, p = 0.011) while patients in Group F tended to have thicker parenchyma (27.39 ± 8.38 vs. 22.88 ± 5.56, p < 0.001). In our analysis of multivariate logistic regression, stone size (OR: 1.074, 1.037-1.113; p < 0.001), lower calyceal location (OR: 0.550, 95% CI 0.364-0.831; p = 0.005), multiple numbers of stones (OR 0.254, 95% CI 0.166-0.389; p =  < 0.001), the value of parenchymal thickness (OR 0.911, 95% CI 0.882-0.941; p =  < 0.001) and more importantly use of anticoagulants/antiplatelets (OR 0.557, 95% CI 0.333-0.933; p = 0.026) appeared to be independent predictors of stone-free status after RIRS. Further evaluation of the data revealed that the cut-off value of the renal parenchymal thickness for an effective stone-free status in a ROC curve analysis was 24.5 with 62.9% sensitivity and 56.8% specificity (area under curve value: 0.654 [95% CI 0.608-0.699, p < 0.001]). The endourologist may be able to make more informed decisions by evaluating renal parenchymal thickness in addition to patient-related factors like anticoagulant use, which we find significantly affects outcomes, along with the stone and renal anatomy-related factors.

Retrograde intrarenal surgery for lower pole stones utilizing stone displacement technique yields excellent results

Objective

To evaluate the long-term stone-free rate (SFR) of retrograde intra-renal surgery (RIRS) in the treatment of lower pole renal calculi using only basket relocation and identify independent predictors of stone-free status.

Methods

All consecutive patients undergoing RIRS lower pole renal calculi at a single high-volume tertiary center were analyzed retrospectively. Lower pole stones were relocated to the upper pole, where laser lithotripsy was performed. All patients were followed up in the clinic following the surgery and yearly thereafter. The stone-free status was assessed with a combination of an abdominal ultrasound and abdominal X-ray, or an abdominal non-contrast computed tomography if the stones were known to be radiolucent.

Results

A total of 480 consecutive patients who underwent RIRS for treatment of lower pole renal calculi, between January 2012 and December 2018, were analyzed from a prospectively maintained database of 3000 ureteroscopies. With a median follow-up time of 18.6 months, the mean SFR was 94.8%. The procedures were unsuccessful in 26 (5.4%) patients due to unreachable stones. The median stone size of the unreachable stones was 12 mm (range 10-30 mm). Multivariable logistic regression analysis revealed two predictors of SFR for lower pole stones: a small cumulative stone burden (odds ratio [OR]: 0.903, 95% confidence interval [CI]: 0.867-0.941, p<0.0001) and preoperative ureteral stent insertion (OR: 0.515, 95% CI: 0.318-0.835, p=0.007).

Conclusion

The long-term SFR of RIRS for the treatment of lower pole stones with basket displacement with appropriate patient selection is high.

The effect of Trendelenburg position on outcomes of retrograde intrarenal surgery for medium sized renal pelvis stones

Aim: To compare safety and efficiency between Trendelenburg position retrograde intrarenal surgery (tRIRS) and conventional position retrograde intrarenal surgery (cRIRS) in the management of renal pelvis stones 10-20 mm in size. Material and Method: From September 2018 to September 2019, the patients undergoing RIRS for single renal stones between 10-20 mm were included in the study prospectively. Patients were divided into two groups randomly. First group of patients were positioned completely parallel to the ground (cRIRS), second group were positioned with Trendelenburg (tRIRS). Success was evaluated at end of 3rd months by non-contrast enhanced tomography. Stones that smaller than 4 mm were accepted as clinical insignificant residual fragment. Complications was classified according to Clavien, class 2 or more complications were recorded. Results: Totally 100 patients were included to final analyze. Patients’ age, gender, stone side and mean stone surface area were similar between groups. Success rate was higher in tRIRS group (90% vs 72% p=0.022). Mean operation time was lower (41.8 vs 58.2 min. p

Development of a novel predictive model for a successful stone removal after flexible ureteroscopic lithotripsy based on ipsilateral renal function: a single-centre, retrospective cohort study in China

OBJECTIVES

The aims of this study were to investigate the effect of preoperative ipsilateral renal function on the success of kidney stone removal with flexible ureteroscopic lithotripsy and to develop a predictive model based on the results.

DESIGN

Retrospective cohort study.

SETTING

Data from the 2001-2012 period were collected from the electronic records of West China Hospital, Sichuan University.

PARTICIPANTS

576 patients who underwent flexible ureteroscopic lithotripsy were included in the study.

PRIMARY OUTCOME

Stone-free rate (SFR) after the procedures.

RESULTS

In patients with suspected impaired kidney function, the overall SFR was 70.1%. Stone volume (OR 1.46; 95% CI 1.18 to 1.80), lower calyx stones (OR 1.80; 95% CI 1.22 to 2.65), age (OR 1.02; 95% CI 1.00 to 1.04), body mass index (OR 1.10; 95% CI 1.04 to 1.17) and estimated glomerular filtration rate of the affected kidney (OR 0.95; 95% CI 0.94 to 0.97) were identified as independent predictors of SFR. Lasso regression selected the same five predictors as those identified by univariate and multivariate logistic regression analyses, thus verifying our model. The mean area under the curve, based on 1000 iterations and 10-fold validation, was 0.715 (95% CI 0.714 to 0.716). The Hodges-Lehmann test and calibration curve analysis revealed no significant mismatch between the prediction model and the retrospective cohort.

CONCLUSION

Ipsilateral renal function may be a novel independent risk factor for kidney stone removal with flexible ureteroscopic lithotripsy. A novel nomogram for predicting SFR that uses stone volume, lower calyx stones, age, body mass index and estimated glomerular filtration rate was developed, but remains to be externally validated.

External validation of efficacy and reliability of different retrograde intrarenal surgery (RIRS) scoring systems for pediatric nephrolithiasis

INTRODUCTION

Retrograde Intrarenal Surgery (RIRS) is one of minimally invasive procedures for pediatric upper urinary stones. However, a RIRS predictive system for children to evaluate postoperative stone free rate (SFR) is still unavailable.

OBJECTIVE

The aim of this study is to validate the efficacy and reliability of different RIRS scoring systems for children.

STUDY DESIGN

We collected clinical data of 137 pediatric patients treated with RIRS in our center between 2014 and 2021. All the predictors were acquired by preoperative non-contrast CT or CT urography. Receiver Operative Curve (ROC) and Area Under Curve (AUC) were showed to compare the predictive power of different models.

RESULTS

A total of 162 RIRS procedures were performed for these 137 pediatric patients. Median surgical duration, irrigation volume and hospitalization were 30 (20, 40) min, 500 (300, 1000) ml and 6 (4, 7) days, respectively. Overall SFR and complication rate was 79.6% (129/162) and 29.2% (40/137), respectively. Significant difference was detected between non-stone free group and stone free group in terms of stone complexity (p < 0.001), cumulative stone sizes [2.3 (2.0, 3.5) cm vs. 1.5 (1.0, 2.0) cm, p < 0.001], RUS groups (p < 0.001), S-ReSC groups (p < 0.001) and RIRS nomogram score [10 (8, 12) vs. 23 (18, 25), p < 0.001]. Among them, RIRS nomogram presented with the maximum AUC values in comparison with the other two systems (RUS: 0.944 vs. 0.874, p = 0.001; S-ReSC: 0.944 vs. 0.808, p < 0.001).

DISCUSSION

We reported the largest sample size of pediatric patients treated with RIRS in our center. Similar with previous studies, RIRS is an efficacious and safe option for pediatric patients. RIRS nomogram showed the best predictive outcome due to the inclusion of multiple parameters, but an innovative predictive system based on pediatric clinical data is warranted in the future.

CONCLUSION

Among the three scoring systems, RIRS nomogram showed the most optimal predictive power of postoperative SFR for pediatric patients.

Outcomes of fluoroscopy-free retrograde intrarenal surgery and predictive factors of stone-free

OBJECTIVE

To evaluate the outcomes of flouroscopy-free retrograde intrarenal surgery (ffRIRS) and to investigate the factors that may affect stone-free rate.

MATERIALS AND METHODS

The charts of patients who underwent ffRIRS between January 2017 and August 2019 were reviewed retrospectively. Patients with missing preoperative imaging and patients with kidney anomalies were excluded from the study. Age, gender, stone size, stone localization, stone density, laterality, operation time, stone-free rate, complications and auxiliary procedures were recorded and analyzed.

RESULTS

Study group involved 44 (43.1%) female and 58 (56.8%) male patients. Stone-free rate in a single-session ffRIRS were found to be correlated with stone localization (p = 0.003), stone volume (p = 0.004), and stone density (p = 0.009) but not with age (p = 0.950). Patients with multiple calyceal stones and a stone burden over 520 mm3 were found to be less stone-free. The complication rate in female gender (n = 7) was significantly higher compared to male (n = 1) (p = 0.011). No major complications such as ureteral injury or avulsion were observed. Overall, 13 patients (12.7%) needed auxiliary procedures. The operation time seemed to be affected by stone size and gender (p = 0.005; p = 0.044, respectively).

CONCLUSIONS

Stone-free rate in ffRIRS were found to be affected by stone density, size, and localization. Patients with multiple caliceal stones and high stone burden (< 520 mm3) have been found to have low stone-free rate, so one can speculate that having fluoroscopy assistance in RIRS might help us to improve surgical success.

External validation of the T.O.HO. score and derivation of the modified T.O.HO. score for predicting stone-free status after flexible ureteroscopy in ureteral and renal stones

OBJECTIVE

The T.O.HO. scoring system was developed to predict stone-free status after flexible ureterenoscopy (fURS) lithotripsy applied for ureter and renal stones. This study aimed to perform the external validation of the T.O.HO. score in the Turkish population and propose a modification for this system.

MATERIAL METHODS

Patients who underwent fURS for kidney and ureteral stones between January 2017 and January 2020 were retrospectively analysed. The patient and stone characteristics and perioperative findings were noted. The T.O.HO. score was externally validated and compared with the STONE score. Stone-free parameters were evaluated with the multivariate analysis. Based on the results of this analysis, the T.O.HO. score was modified and internally validated.

RESULTS

A total of 621 patients were included in the study. The stone-free rate was determined as 79.8% (496/621) after fURS. The regression analysis showed that stone area had better predictive power than stone diameter (P = .025). Lower pole (reference), middle pole [odds ratio (OR) = 0.492 P = .016] and middle ureteral (OR = 0.227, P = .024) localisations, stone density (OR = 1.001, P < .001), and stone volume (OR = 1.008, P < .001) were determined as independent predictive markers for stone-free status. Based on the effect size of the stone surface area in the nomogram, stone volume was divided into five categories, at 1-point intervals. The AUC values of the T.O.HO., STONE, and modified T.O.HO. score in predicting stone-free status were calculated as 0.758, 0.634, and 0.821, respectively. The modified T.O.HO. created by adding stone volume was statistically significantly superior to the original version (ROC curve comparison, P < .001).

CONCLUSION

The T.O.HO. score effectively predicted stone-free status after fURS. However, modified T.O.HO. SS showed the best predictive performance compared with original T.O.HO. SS.

The effect of optical dilatation before retrograde intrarenal surgery on success and complications: Results of the RIRSearch group study

AIM

The guidelines propose optical dilatation before retrograde intrarenal surgery (RIRS), but there are currently no evidence-based studies concerning the impact of optical dilatation with semirigid ureteroscopy (sURS). The aim of this study was to evaluate the effect of optical dilatation through sURS prior to the RIRS procedure on the success and complications of RIRS.

METHODS

A total of 422 patients were included in the retrospective multicentre study. The patients were divided into two groups according to whether sURS was to be performed. Patients' demographics, stone parameters and operative outcomes were compared. Surgical success was defined as no or up to 3-mm residual stone fragments without the need for additional procedures. The independent predictors for surgical success were determined with a multivariable logistic regression model.

RESULTS

Of the 422 patients, 133 (31.5%) were in the sURS group and 289 (68.5%) were in the non-sURS group. Stone characteristics and patients' demographics were similar between the groups. Operation time in the sURS group was significantly longer (compared with the non-sURS group, P < .0001). A ureteral access sheath (UAS) could not be placed in four (3.0%) patients in the sURS group, nor in 25 (8.7%) patients in the non-sURS group (P = .03). Compared with the non-sURS group, the intraoperative complication rate was lower in the sURS group (14 [4.8%] vs 1 [0.8%], P = .04). The surgical success rate was higher in the sURS group (P = .002). Nevertheless, sURS had no independent effect on surgical success. We found two independent predictors for surgical success rate: stone number (P < .0001, OR:2.28) and failed UAS placement (P = .035, OR:3.49).

CONCLUSIONS

Optical dilatation with sURS before RIRS increases surgical success by raising the rate of UAS placement and reducing the rate of intraoperative complications. We suggest that this method can be routinely applied to patients who have not been passively dilated with a JJ stent.

Efficacy of various laser devices on lithotripsy in retrograde intrarenal surgery used to treat 1-2 cm kidney stones: A prospective randomized study

AIMS

To compare the efficacy of different laser devices and power ranges on lithotripsy in retrograde intrarenal surgery (RIRS) for 1-2 cm kidney stones.

METHODS

A total of 223 participants undergoing RIRS for 1-2 cm kidney stones at our clinic between January 2015 and January 2017 were recruited for this prospective study (NCT02451319). Two hundred and four participants included in our study were randomly allocated into either ≤20 W with 20 W laser device (group 1) or ≤20 W with 30 W laser device (group 2) or >20 W with 30 W laser device (group 3).

RESULTS

There was no significant difference between the groups in terms of demographic and stone characteristics. Operation and fluoroscopy times were significantly longer (P = .003 and P < .001, respectively) and stone-free rate (SFR) was significantly lower in group 1 (P = .002). Complications were similar in all three groups (P = .512). However, post-operative pain scores were significantly higher in group 1 (P < .001). The multivariate analysis revealed that stone size (95% CI: 0.654-0.878, OR = 0.758, P < .001), ureteral access sheath use (95% CI: 1.003-20.725, OR = 4.560, P = .049), and lithotripsy with 30 W laser device (95% CI: 1.304-11.632, OR = 3.895, P = .015; 95% CI: 1.738-17.281, OR = 5.480, P = .004, groups 2 and 3, respectively) were independent factors predicting SFR for RIRS used in 1-2 cm kidney stones.

CONCLUSION

The 30 W laser device used in RIRS for 1-2 cm kidney stones had shorter operation times, higher SFRs, and lower post-operative pain scores compared with the 20 W device. The 30 W laser device is safe and more efficient in RIRS for treatment of 1-2 cm kidney stones.

External validation and comparison of current scoring systems in retrograde intrarenal surgery: Multi-institutional study with 949 patients

OBJECTIVES

To externally validate and compare Resorlu-Unsal stone score (RUSS), modified Seoul National University Renal Stone Complexity Score(S-ReSC), Ito's nomogram, and Retrograde Intra-Renal Surgery (R.I.R.S.) scoring systems for predicting capabilities of both the stone-free status and complications in a multi-institutional study.

MATERIALS AND METHODS

We performed a retrospective analysis of 949 patients who underwent flexible ureterorenoscopy (f-URS) and laser lithotripsy for renal stones in two institutions between March-2015 and June-2020. The RUSS, modified S-ReSC, Ito's nomogram, and R.I.R.S. scores were calculated for each patient by the same surgeon on imaging methods. Results were compared for their predictive capability of stone-free status and complications.

RESULTS

Of 949 patients 603 were male and 346 were female with a mean age of 47.2 ± 14.3 (range 2-84 years). Mean stone burden was 102.6 ± 42.2 (48-270 mm² ). All nomograms predicted stone-free status (Area Under Curve (AUC) were 0.689, 0.657, 0.303, and 0.690, respectively). All four scoring systems predicted complications with AUC values of 0.689, 0.646, 0.286, and 0.664 for RUSS, modified S-ReSC, Ito's nomogram, and R.I.R.S., respectively. Although all scoring systems were able to predict complications only Ito's nomogram was able to predict Clavien ≥2 complications.

CONCLUSION

All four scoring systems (RUSS, modified S-ReSC, Ito's nomogram, and R.I.R.S.) could predict stone-free status after f-URS, however, the AUC values are not satisfactory in our large patient cohort. Although these scoring systems were not developed for predicting post-operative complications, they were associated with complications in our study. However, these four scoring systems have some significant limitations. The ideal scoring system is yet to be developed.

Atlas of scoring systems, grading tools and nomograms in Endourology: A comprehensive overview from The TOWER Endourological Society research group

INTRODUCTION

With an increase in the prevalence of kidney stone disease (KSD), there has been a universal drive to develop reliable and user-friendly tools such as grading systems and predictive nomograms. An atlas of scoring systems, grading tools and nomograms in Endourology is provided in this paper.

METHODS

A comprehensive search of world literature was performed to identify nomograms, grading systems and classification tools in endourology related to KSD. Each of these were reviewed by the authors and have been evaluated in a narrative format with details on those which are externally validated and their respective citation count on google scholar.

RESULTS

A total of 54 endourological tools have been described in our atlas of endourological scoring systems, grading tools and nomograms. Of the tools, 23 (43%) are published in the last 3 years showing an increasing interest in this area. This includes 5 for percutaneous nephrolithotomy (PCNL), 6 for flexible ureteroscopy (fURS), 3 for semi-rigid URS (sURS), 9 for shockwave lithotripsy (SWL), 2 for stent encrustations, 3 for intra-operative appearance at the time of URS and 3 to classify intra-operative ureteric injury. There were 3 tools for renal colic assessment, one each for prediction of future stone event, stone classification and stone impaction and 2 for need of emergency intervention in ureteric stone. While 2 tools are related to stone recurrence, 6 are related to post-procedural complications. There are now 2 tools for simulation in endourology and 5 for patient reported outcome measures (PROMS).

CONCLUSIONS

A number of reliable and established tools exist currently in endourology. Each of these offers their own respective advantages and disadvantages. While nomograms and scoring systems can help in the decision making, these must be tailored to individual patients based on their specific clinical scenarios, expectations and informed consent.

What Do We Mean by "Stone Free," and How Accurate Are Urologists in Predicting Stone-Free Status Following Ureteroscopy?

Background and Purpose: No consensus exists on how stone-free rates (SFRs) should be reported after stone treatment. The aim of this study was to assess how accurate urologists predict their patients being stone free after completing ureteroscopy (URS) and to see how various treatment strategies influenced the precision of these predictions. We also wanted to study how different definitions of stone-free status (SFS) affected the results and propose a standard definition of "stone free" to be used in future studies. Materials and Methods: A retrospective evaluation of 1019 URS done for stone treatment at Haukeland University Hospital between 2013 and 2018 was performed. Data on pretreatment status, the surgical procedure, and follow-up were recorded. SFS was defined as either no fragments detected on computed tomography (CT) after 3 months or as practical stone-free status, which also included those with small residual fragments not needing further treatment. Exact chi-squared and independent-samples t-tests were used comparing data between different treatment modalities. Results: The overall SFR, irrespective of treatment strategy and location of stone, using the no residual fragments and practical stone-free definitions were 54.2% and 74.7%, respectively. Urologists predicted intraoperatively that 91.0% of their patients treated with fragmentation and extraction would be stone free compared to 76.8% of patients treated with dusting, p < 0.0001. At follow-up, the actual SFRs with no residual fragments for the two treatment strategies were 68.0% and 35.5%, respectively, p < 0.0001. The practical SFRs for fragmentation and retrieval were 83.1% and 64.8% for dusting, p < 0.0001. Conclusion: The different definitions of SFS have great impact on SFRs. Urologists are far too optimistic predicting their patient being stone free after URS. SFS should be defined as no fragments detected on CT 3 months after the URS procedure when presented in studies.

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

Purpose: The purpose of the study is to develop and validate a novel clinical-radiomics nomogram model for pre-operatively predicting the stone-free rate of flexible ureteroscopy (fURS) in kidney stone patients. Patients and Methods: Altogether, 2,129 fURS cases with kidney stones were retrospectively analyzed, and 264 patients with a solitary kidney stone were included in a further study. For lower calyx calculi, a radiomics model was generated in a primary cohort of 99 patients who underwent non-contrast-enhanced computed tomography (NCCT). Radiomics feature selection and signature building were conducted by using the least absolute shrinkage and selection operator (LASSO) method. Multivariate logistic regression analysis was employed to build a model incorporating radiomics and potential clinical factors. Model performance was evaluated by its discrimination, calibration, and clinical utility. The model was internally validated in 43 patients. Results: The overall success rate of fURS was 72%, while the stone-free rate (SFR) for lower calyx calculi and non-lower calyx calculi was 56.3 and 90.16%, respectively. On multivariate logistic regression analysis of the primary cohort, independent predictors for SFR were radiomics signature, stone volume, operator experience, and hydronephrosis level, which were all selected into the nomogram. The area under the curve (AUC) of clinical-radiomics model was 0.949 and 0.947 in the primary and validation cohorts, respectively. Moreover, the calibration curve showed a satisfactory predictive accuracy, and the decision curve analysis indicated that the nomogram has superior clinical application value. Conclusion: In this novel clinical-radiomics model, the radiomics scores, stone volume, hydronephrosis level, and operator experience were crucial for the flexible ureteroscopy strategy.

In Vitro Evaluation of Stone Fragment Evacuation by Suction

Introduction: Contemporary, flexible stone baskets are unable to extract submillimeter stone fragments at the time of ureteroscopic laser lithotripsy. In this in vitro study, the feasibility of suctioning submillimeter fragments with a standard Luer Lock syringe through the working channel of a flexible ureteroscope was assessed. Materials and Methods: Phantom stones made from industrial plaster were mechanically fragmented into ≤1 and ≤0.5-mm groups. Both stone groups were divided into five preweighed trial samples. Each stone group was then mixed in a beaker filled with normal saline. A standard 10-mL Luer Lock syringe was connected to a fiber-optic ureteroscope with a 1.2-mm working channel. The syringe was then used to suction stone fragments from the beaker. The suctioned stone fragments and the stone fragments remaining in the beaker after removing the overlying solution were separated, centrifuged with supernatant removed, and dried in an incubator set at 33°C for 1 week. Dried weights were recorded. Results: Mean total weights for ≤0.5 and ≤1.0-mm stone groups at baseline were 0.807 and 0.806 g, respectively. The mean percentages of stone fragments suctioned through the ureteroscope for ≤0.5 and ≤1.0-mm groups were 86% and 86%, respectively (p = 0.973). During suctioning, 64% of stones in the ≤0.5-mm group were trapped in either the working channel of the ureteroscope or within the Luer Lock syringe compared with 78% of stones in the ≤1-mm group (p = 0.001) requiring cessation of the procedure to clear the channel. Conclusions: It is feasible to suction submillimeter stone fragments by connecting a Luer Lock syringe to the working channel of a flexible ureteroscope. The limiting factor for removing stone fragments appears to be the small working channel of flexible ureteroscopes as trapping of fragments during suctioning is common and requires time-consuming removal of the endoscope and clearing of the channel.

Evaluation and comparison of scoring systems for predicting stone-free status after flexible ureteroscopy for renal and ureteral stones

OBJECTIVE

To evaluate four predictive scores for stone-free rate (SFR) after flexible ureterorenoscopy (f-URS) with holmium-YAG laser fragmentation of renal and ureteral lithiasis.

METHODS

We carried out a retrospective analysis of 800 f-URS procedures performed in our institution between January 2009 and December 2016. For each procedure, a single surgeon calculated the following scores: S.T.O.N.E score; Resorlu Unsal Stone Score (RUSS); modified Seoul National University Renal Complexity (S-ReSC) score; and Ito's score.

RESULTS

Overall SFR was 74.1%. Univariate analysis demonstrated that stone size (p<0.0001), stone volume (p<0.0001), stone number (p = 0.004), narrow lower pole infundibulopelvic angle (IPA) (p = 0.003) and lower pole location + IPA <45° (p = 0.011) were significantly associated with SFR. All scores differed between the stone-free and non-stone-free groups. Area under the curve of the receiving operator characteristics curve was calculated for each score: 0.617 [95%CI: 0.575-0.660] for the S.T.O.N.E score; 0.644 [95%CI: 0.609-0.680] for the RUSS; 0.651 [95%CI: 0.606-0.697] for the S-ReSC score; and 0.735 [95%CI: 0.692-0.777] for Ito's nomogram.

CONCLUSION

All four scores were predictive of SFR after f-URS. Ito's score was the most sensitive. However, the performance of all scores in this analysis was lower than in developmental studies.

Does the renal parenchymal thickness affect the efficacy of the retrograde intrarenal surgery? A prospective cohort study

Retrograde intrarenal surgery (RIRS) is one of the minimally invasive main treatment modalities in renal stone disease. There are many factors which affect stone-free rate (SFR). Our study was based on the hypothesis that higher renal parenchymal thickness (RPT) which may include higher average number of nephrons provides better diuresis. We investigated the efficacy of RPT on success of RIRS. This study is a single-centered prospective surgical cohort study. A total of 383 patients were analyzed. Regularly followed 304 patients with unilateral kidney stone at single pole or renal pelvis and who underwent single-session RIRS were included in the final analysis, and the patients' preoperative and postoperative 1st and 3rd months' data were evaluated. RPT was measured on the non-contrast computed tomography (CT) images. ROC analysis was performed to estimate the cutoff value of RPT for SFR. Univariate and multivariate logistic regression analyses were used to model the relationship between RPT and SFR after RIRS. ROC analysis revealed the best cutoff value of the RPT for predicting residual stone as 19 mm for both the 1st and 3rd month visits with Youden indexes of 0.397 and 0.406, respectively. To the best of our knowledge, this is the first study which evaluated the effect of RPT on the efficacy of RIRS. RPT measurement is a cost-effective method that can be easily performed on routinely applied non-contrast CT and may have predictive value for the surgical success in patients with nephrolithiasis.

Computed tomography window affects kidney stones measurements

OBJECTIVES

Measurements of stone features may vary according to the non-contrast computed tomography (NCCT) technique. Using magnified bone window is the most accurate method to measure urinary stones. Possible differences between stone measurements in different NCCT windows have not been evaluated in stones located in the kidney. The aim of this study is to compare measurements of kidney stone features between NCCT bone and soft tissue windows in patients submitted to retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

Preoperative and 90th postoperative day NCCT were performed in 92 consecutive symptomatic adult patients (115 renal units) with kidney stones between 5 mm to 20 mm (< 15 mm in the lower calyx) treated by RIRS. NCCT were evaluated in the magnified bone window and soft tissue window in three axes in a different time by a single radiologist blinded for the measurements of the NCCT other method.

RESULTS

Stone largest size (7.92±3.81 vs. 9.13±4.08; mm), volume (435.5±472.7 vs. 683.1±665.0; mm3) and density (989.4±330.2 vs. 893.0±324.6; HU) differed between bone and soft-tissue windows, respectively (p<0.0001) 5.2% of the renal units (6/115) were reclassified from residual fragments > 2 mm on soft tissue window to 0-2 mm on bone window.

CONCLUSION

Kidney stone measurements vary according to NCCT window. Measurements in soft tissue window NCCT of stone diameter and volume are larger and stone density is lesser than in bone window. These differences may have impact on clinical decisions.

[Application of machine learning models in predicting early stone-free rate after flexible ureteroscopic lithotripsy for renal stones]

OBJECTIVE

To establish predictive models based on random forest and XGBoost machine learning algorithm and to investigate their value in predicting early stone-free rate (SFR) after flexible ureteroscopic lithotripsy (fURL) in patients with renal stones.

METHODS

The clinical data of 201 patients with renal stones who underwent fURL were retrospectively investigated. According to the stone-free standard, the patients were divided into stone-free group (SF group) and stone-residual group (SR group). We compared a number of factors including patient age, body mass index (BMI), stone number, stone volume, stone density and hydronephrosis between the two groups. For low calyceal calculi, renal anatomic parameters including infundibular angle (IPA), infundibular width (IW), infundibular length (IL) and pelvic calyceal height (PCH), would be measured. We brought above potential predictive factors into random forest and XGBoost machine learning algorithm respectively to develop two predictive models. The receiver operating characteristic curve (ROC curve) was established in order to test the predictive ability of the model. Clinical data of 71 patients were collected prospectively to validate the predictive models externally.

RESULTS

In this study, 201 fURL operations were successfully completed. The one-phase early SFR was 61.2%. We built two predictive models based on random forest and XGBoost machine learning algorithm. The predictive variables' importance scores were obtained. The area under the ROC curve (AUROC) of the two predictive models for early stone clearance status prediction was 0.77. In the study, 71 test samples were used for external validation. The results showed that the total predictive accuracy, predictive specificity and predictive sensitivity of the random forest and XGBoost models were 75.7%, 82.6%, 60.0%, and 81.4%, 87.0%, 68.0%, respectively. The first four predictive variables in importance were stone volume, mean stone density, maximal stone density and BMI in both random forest and XGBoost predictive models.

CONCLUSION

The predictive models based on random forest and XGBoost machine learning algorithm can predict postoperative early stone status after fURL for renal stones accurately, which will facilitate preoperative evaluation and clinical decision-making. Stone volume, mean stone density, maximal stone density and BMI may be the important predictive factors affecting early SFR after fURL for renal stones.

An artificial intelligence-based clinical decision support system for large kidney stone treatment

A decision support system (DSS) was developed to predict postoperative outcome of a kidney stone treatment procedure, particularly percutaneous nephrolithotomy (PCNL). The system can serve as a promising tool to provide counseling before an operation. The overall procedure includes data collection and prediction model development. Pre/postoperative variables of 254 patients were collected. For feature vector, we used 26 variables from three categories including patient history variables, kidney stone parameters, and laboratory data. The prediction model was developed using machine learning techniques, which includes dimensionality reduction and supervised classification. A novel method based on the combination of sequential forward selection and Fisher's discriminant analysis was developed to reduce the dimensionality of the feature space and to improve the performance of the system. Multiple classifier scheme was used for prediction. The derived DSS was evaluated by running leave-one-patient-out cross-validation approach on the dataset. The system provided favorable accuracy (94.8%) in predicting the outcome of a treatment procedure. The system also correctly estimated 85.2% of the cases that required stent placement after the removal of a stone. In predicting whether the patient might require a blood transfusion during the surgery or not, the system predicted 95.0% of the cases correctly. The results are promising and show that the developed DSS could be used in assisting urologists to provide counseling, predict a surgical outcome, and ultimately choose an appropriate surgical treatment for removing kidney stones.

Size is Not Everything That Matters: Preoperative CT Predictors of Stone Free After RIRS

OBJECTIVE

To define computed tomography (CT) predictors of residual fragments after retrograde intrarenal surgery (RIRS) for kidney stones up to 20 mm in patients never submitted to surgical procedures for stone removal.

METHODS

From August 2016 to August 2017, symptomatic adult patients with kidney stones less than 20 mm treated by RIRS had their pre- and postoperative CT prospectively evaluated in search for predictors of residual stone fragments. Stone size, stone volume, number of stones, stone density, and location were evaluated in preoperative CT and analyzed as predictors for residual stone fragments on 90 POD CT. Stone location was represented by the infundibulopelvic angle (IPA) measured for each stone on preoperative noncontrast CT using multiplanar reconstruction.

RESULTS

Ninety-two patients were successfully submitted to RIRS. Bilateral procedures were performed in 23 patients (25%) resulting in 115 renal units operated. Operative time was 54.5 ± 26.7 minutes (mean ± SD) and 96.7% (89/92) of the patients were discharged up to 12 hours after the procedure. Postoperative CT demonstrated stone-free in 86 of 115 (74.8%), 0-2 mm in 10 of 115 (8.7%), and > 2 mm residual fragments in 19 of 115 (16.5%) procedures. Logistic regression analysis revealed steep IPA was a predictor for any residual stone fragment after RIRS for kidney stones < 20 mm (P= .012). ROC curve showed that IPA < 41° was associated with a higher chance of residual fragments after RIRS.

CONCLUSION

IPA < 41° is associated with a higher chance of residual fragments after RIRS for kidney stones up to 20 mm.

Prediction of stone-free status after single-session retrograde intrarenal surgery for renal stones

OBJECTIVE

To determine the possible factors effecting stone-free status (SFS) after single-session retrograde intrarenal surgery (RIRS) for renal stones.

MATERIAL AND METHODS

We retrospectively analyzed the charts of 100 consecutive patients who underwent RIRS. Unilateral procedures performed for single renal stones were included in the study. The studied parameters included patient demographics, stone characteristics (size, volume, location and attenuation according to Hounsfield unit [HU]), operation time, presence of preoperative double-J stent (DJS), use of ureteral access sheath (UAS) and SFS.

RESULTS

The study population consisted of 100 patients where 43 of them were stone free and remaining 57 had residual stones. The mean age of the patients was 47.2±13.4 years. The mean stone size (largest dimension), stone attenuation and stone volume were 14.8±5.8 mm, 1010±416 HU and 937±929 mm³, respectively. The mean operative time was 60.8±24.2 minutes. Mean stone size, volume and HU were higher in the RS group compared to SF group but without any statistically significant difference, 15.2±6.1 vs. 14.2±5.3 mm, 1056±1037 mm³ vs. 780±745 mm³ and 1061±374 HU vs. 942±462 HU, respectively (p=0.490, p=0.135 and p=0.226). In multivariate regression analysis stone location and UAS use were found to be the significant predictors of SFS. Patients with lower pole stones are 2.25 times likely to have residual stones after RIRS compared to patient's having stones at other localizations (p<0.001).

CONCLUSION

Stone volume could be a more reliable parameter than stone size in predicting RIRS success. Lower pole stone location and UAS use could be considered the most significant predictors of SFS after single session RIRS for single renal stones.

Comparison of Outcomes between Two Methods to Extract Stone Fragments during Flexible Ureteroscopic Lithotripsy

Objectives

To retrospectively compare the operative and clinical outcomes of flexible ureteroscopic lithotripsy (fURSL) with stone extraction performed either by a surgeon (SE) who manipulates the retrieval basket or by having the surgical assistant (AE) manipulate the retrieval basket with the aim of clarifying which method provides a greater stone-free postoperative status.

Methods

The study group consisted of patients who underwent fURSL with SE or AE at our institution between April 2015 and December 2016. Demographic, clinical, stone, and operative variables were compared between the two groups. Multivariate logistic regression was used to identify risk factors associated with a stone-free and non-stone-free status postoperatively.

Results

Our analysis included 196 cases of renal stones treated using fURSL, with 109 who underwent AE and 87 who underwent SE. The rate of stone-free status was higher for the SE group (90.8%) than for the AE group (61.5%; P < 0.001). The method of extraction was identified as an independent predictor of stone-free status (P < 0.001, odds ratio (SE compared to AE), 9.133, 95% confidence interval, 3.736–22.322).

Conclusion

The stone-free rate is improved by having the surgeon perform the stone extraction as part of the fURSL procedure.

[Result of treatment of urinary lithiasis for professional aptitude]

INTRODUCTION

Military people are inapt for presence of urinary stones. In this specific population, the treatment of stones is even more aggressive than for the general population without recommendation. The final decision about aptitude is the responsibility of the military doctor. Whereas, ureteroscopy has its place there and must done by any urologist.

METHODS

The purpose of this study was to estimate the results of treatments by ureteroscopy in this population. Success was defined by the complete absence of fragment visualized in the imaging of control operating comment and so the end of the inaptitude time.

RESULTS

Between 2009 and 2016, forty-two were treated for ureteral or renal calculi. The population comprises of 93% men, 35 years old on average. The stones were mainly multiple (more 2) and the medium size is 5mm; sixteen (42.9%) was at the left and eight (19%) was bilateral. In 78.8% (78) of the cases there was a stone in renal position whose 50% (39) still at the lower calyx. In total, 5% of the patients were stone-free in 2 sessions on average. The average deadline of inaptitude of the initial consultation in the resumption of work was of 6 months. In 4% of the cases there was a complication operating rank 4.

CONCLUSION

This study confirms the feasibility, the weak harmlessness of ureteroscopy and the lesser deadline of inaptitude. Every urologist can treat this specific population. The patient must be informed and accept the treatment because of excluding referential.

LEVEL OF EVIDENCE

4.

Experiencia en el manejo de litiasis renal y ureteral con ureteroscopio flexible y láser holmium en un hospital público de Bogotá: estudio retrospectivo

Objetivos Discutir y evaluar la tasa libre de cálculos y las complicaciones de la ureterolitotomía endoscópica flexible con láser holmium en el manejo de cálculos ureterales y renales basada en la experiencia de un hospital público de iii nivel en Bogotá.

Material and Métodos Estudio retrospectivo en una muestra poblacional en pacientes con litiasis renal y ureteral, tratados con ureteroscopio flexible y láser holmium, evaluándose la tasa libre de cálculos, complicaciones postoperatorias y otros parámetros. El seguimiento se realizó con radiografía de abdomen y urotac al mes del postoperatorio, la tasa libre de cálculos se definió como ausencia de cálculos residuales < 4 mm en la imagen control.

Resultados Se realizaron 44 procedimientos en 43 pacientes con edad promedio de 45 años, tiempo quirúrgico promedio 91,2 min, la tasa libre de cálculos fue del 84% (37/44) en un solo evento quirúrgico; solo un paciente requirió una segunda intervención con posterior tasa libre de cálculos del 100%. La tasa libre de cálculos ureterales fue del 92% (24/26), cáliz superior 100% (2/2), cáliz medio 100%(1/1), cáliz inferior 78% (7/9) y calicial múltiple 50% (3/6). El porcentaje de complicaciones fue del 6,8%.

Conclusiones La ureterolitotomía endoscópica flexible con láser es un procedimiento efectivo y seguro en el manejo de litiasis renal y ureteral con baja incidencia de complicaciones. Observamos que en la mayoría de los pacientes con fragmentos residuales significativos estos se encontraban en cáliz inferior o se trataba de cálculos en múltiples cálices, explicándose por el difícil acceso al cáliz inferior y la carga litiásica.

A new prediction model for operative time of flexible ureteroscopy with lithotripsy for the treatment of renal stones

This study aimed to develop a prediction model for the operative time of flexible ureteroscopy (fURS) for renal stones. We retrospectively evaluated patients with renal stones who had been treated successfully and had stone-free status determined by non-contrast computed tomography (NCCT) 3 months after fURS and holmium laser lithotripsy between December 2009 and September 2014 at a single institute. Correlations between possible factors and the operative time were analyzed using Spearman’s correlation coefficients and a multivariate linear regression model. The P value < 0.1 was used for entry of variables into the model and for keeping the variables in the model. Internal validation was performed using 10,000 bootstrap resamples. Flexible URS was performed in 472 patients, and 316 patients were considered to have stone-free status and were enrolled in this study. Spearman’s correlation coefficients showed a significant positive relationship between the operation time and stone volume (ρ = 0.417, p < 0.001), and between the operation time and maximum Hounsfield units (ρ = 0.323, p < 0.001). A multivariate assessment with forced entry and stepwise selection revealed six factors to predict the operative time of fURS: preoperative stenting, stone volume, maximum Hounsfield unit, surgeon experience, sex, and sheath diameter. Based on this finding, we developed a model to predict operative time of fURS. The coefficient of determination (R²) in this model was 0.319; the mean R² value for the prediction model was 0.320 ± 0.049. To our knowledge, this is the first report of a model for predicting the operative time of fURS treatment of renal stones. The model may be used to reliably predict operative time preoperatively based on patient characteristics and the surgeons’ experience, plan staged URS, and avoid surgical complications.

The R.I.R.S. scoring system: An innovative scoring system for predicting stone-free rate following retrograde intrarenal surgery

Background

To establish and internally validate an innovative R.I.R.S. scoring system that allows urologists to preoperatively estimate the stone-free rate (SFR) after retrograde intrarenal surgery (RIRS).

Methods

This study included 382 eligible samples from a total 573 patients who underwent RIRS from January 2014 to December 2016. Four reproducible factors in the R.I.R.S. scoring system, including renal stone density, inferior pole stone, renal infundibular length and stone burden, were measured based on preoperative computed tomography of urography to evaluate the possibility of stone clearance after RIRS.

Results

The median cumulative diameter of the stones was 14 mm, and the interquartile range was 10 to 21. The SFR on postoperative day 1 in the present cohort was 61.5% (235 of 382), and the final SFR after 1 month was 73.6% (281 of 382). We established an innovative scoring system to evaluate SFR after RIRS using four preoperative characteristics. The range of the R.I.R.S. scoring system was 4 to 10. The overall score showed a great significance of stone-free status (p < 0.001). The area under the receiver operating characteristic curve of the R.I.R.S. scoring system was 0.904.

Conclusions

The R.I.R.S. scoring system is associated with SFR after RIRS. This innovative scoring system can preoperatively assess treatment success after intrarenal surgery and can be used for preoperative surgical arrangement and comparisons of outcomes among different centers and within a center over time.

Retrograde intrarenal surgery for renal stones - Part 2

Retrograde intrarenal surgery (RIRS) has become an effective and safe treatment modality in the management of urinary system stone disease. Recent developments and innovations in the flexible ureterorenoscope and auxiliary equipment have made this procedure easier and more effective with increased success rates. RIRS can be used as a primary treatment in patients with renal stones smaller than 2 cm, prior unsuccessful shock wave lithotripsy, infundibular stenosis, renoureteral malformation, skeletal-muscular deformity, bleeding diathesis and obese patients. In the second part of this detailed review for RIRS, effect of stone composition on success rate, preoperative assessment of stone-free rate, the cost of this modality, education for RIRS, fluoroscopy use, the current role of RIRS in the treatment of various urolithiasis types and special conditions, and combined treatment methods are discussed with up-to-date literature.

To Dust or Not To Dust: a Systematic Review of Ureteroscopic Laser Lithotripsy Techniques

PURPOSE OF REVIEW

This review discusses factors affecting outcomes during ureteroscopy (URS) with laser lithotripsy (LL), explores specific clinical challenges to the efficacy of URS LL, and reviews the available literature comparing the dusting and basketing approaches to URS LL.

RECENT FINDINGS

Data show high stone-free rates with URS LL in all locations of the urinary tract and with all stone types and sizes. Recent data comparing LL with dusting versus basketing suggest higher rates of residual fragments with dusting but less utilization of ureteral access sheaths and potentially shorter operative times. Differences in postoperative complications, re-intervention rates, and other outcome parameters are not yet clear. Interpretation of published data is problematic due to variability in laser settings, follow-up intervals, and definitions for what constitutes stone-free status. URS has overtaken shock wave lithotripsy in the last decade as the most commonly utilized surgical approach for treating urolithiasis. Two primary strategies have emerged as the most common techniques for performing LL: dusting and basketing. There is a relative paucity of data examining the difference in these techniques as it pertains to peri-operative outcomes and overall success. We attempt to synthesize this data into evidence-based and experience-based recommendations.

Flexible ureteroscopy for renal stone without preoperative ureteral stenting shows good prognosis

Purpose

To clarify the outcome of flexible ureteroscopy (fURS) for management of renal calculi without preoperative stenting.

Methods

A total of 171 patients who received 176 fURS procedures for unilateral renal stones were reviewed. All procedures were divided into two groups depending on whether they received ureteral stenting preoperatively. Baseline characteristics of patients, stone burden, operation time, stone-free rates, and complications were compared between both groups.

Results

Successful primary access to the renal pelvis was achieved in 104 of 114 (91.2%) patients without preoperative stenting, while all procedures with preoperative stenting (n = 62) were successfully performed. A total of 156 procedures were included for further data analysis (56 procedures in stenting group and 100 in non-stenting group). No significant differences was found regardless of a preoperative stent placement in terms of stone-free rate (73.2% with stenting vs. 71.0% without, P = 0.854), operative time (70.4 ± 32.8 with stenting vs. 70.2 ± 32.1 without, P = 0.969).

Conclusions

fURS for management of renal stone without preoperative ureteral stenting are associated with well outcome in short term follow-up. Our study may help patients and doctors to decide if an optional stent is placed or not.

External Comparison of Recent Predictive Nomograms for Stone-Free Rate Using Retrograde Flexible Ureteroscopy with Laser Lithotripsy

OBJECTIVE

To assess and compare the applicability of the Resorlu-Unsal Stone Score (RUSS) and the Modified Seoul National University Renal Stone Complexity (S-ReSC) score for flexible ureterorenoscopy (f-URS).

PATIENTS AND METHODS

We retrospectively analyzed the hospital files of 719 patients who had been treated with f-URS for kidney stone at two referral centers between July 2012 and December 2015. The RUSS and Modified S-ReSC scores were calculated by the same surgeon for each patient by using imaging methods and were compared as to their predictive capability for postoperative success.

RESULTS

A total of 339 patients (168 men and 171 women) with a mean age of 46.5 ± 16.1 (range:1-86) years and a mean body mass index of 27.1 ± 4.1 (range: 12.8-38.5) were included in the study. The mean stone size was 14.4 ± 5.4 (4-40) mm, and the mean stone surface area was 145.3 ± 76.8 (20-658) mm². The overall stone-free rate was 70.1%. The mean scores were 0.5 ± 0.7 and 1.8 ± 1.1 for the RUSS and Modified S-ReSC, respectively. In the logistic regression analysis, musculoskeletal deformity, stone size, and the RUSS were identified as independent predictive factors affecting stone-free status (p: 0, p: 0.014, p: 0.048, respectively). Among these parameters, the RUSS had the highest predictive capability (area under curve value 0.65, [95% confidence interval 589, 721]).

CONCLUSIONS

Stone size, presence of musculoskeletal abnormalities, and the RUSS score are important factors affecting SF status after f-URS. Despite the RUSS being an independent predictive factor for SF status, more comprehensive systems with higher predictive capability are needed for clinical usage and academic reporting.