Multicenter External Validation and Comparison of Stone Scoring Systems in Predicting Outcomes After Percutaneous Nephrolithotomy

Does success in percutaneous nephrolithotomy depend only on stone size? Analysis of the predictive capacity for success and complications of the current nephrolithometry scoring systems and their relationship with the stone surface

OBJECTIVE

To analyze the predictive capacity of the nephrolithometry scoring systems (GSS, STONE, CROES and S-ReSC) and stone surface regarding success and complications following percutaneous nephrolithotomy (PCNL).

METHODS

We studied 392 patients who had undergone PCNL in our center. Only patients with a non-contrast CT (n = 240) were finally included for analysis. The predictive capacities for success and complications of the different scoring systems were evaluated using ROC curves and their area under the curve (AUC).

RESULTS

Regarding success, the S-ReSC system had the highest predictive capacity with an AUC of 0.681 (95% CI 0.610-0.751), followed by the CROES with 0.667 (95% CI 0.595-0.738), the STONE with 0.654 (95% CI 0.579-0.728) and finally the GSS with 0.626 (95% CI 0.555-0.698). The stone surface as a single variable had an AUC of 0.641 (95% CI 0.565-0.718). As for complications, the S-ReSC had the highest AUC with 0.664 (95% CI 0.57-0.758), followed by STONE with 0.663 (95% CI 0.572-0.755), GSS with 0.626 (95% CI 0.555).-0.698) and CROES with 0.614 (95% CI 0.518-0.7). The stone surface alone had an AUC of 0.616 (95% CI 0.522-0.715).

CONCLUSION

The nephrolithometry scales analyzed show a moderate predictive capacity for success and complications in patients undergoing PCNL in our center. Moreover, stone surface as an independent variable demonstrates moderate predictive capacity for both outcomes.

Comparison of STONE Score, Guy's Stone Score, CROES Nomogram, and Seoul National University Renal Stone Complexity Score in Prognosticating Outcomes of Multiple-Tract Mini-Percutaneous Nephrolithotomy: A Retrospective Study

Objective  The objective of this study was to compare the STONE score (Size of the stone, Topography or location, degree of Obstruction of the urinary system, Number of stones, and Evaluation of Hounsfield units), Guy's stone score (GSS), Clinical Research Office of the Endourological Society (CROES) nomogram, and Seoul National University Renal Stone Complexity Score (RSCS) in prognosticating multiple tract mini-percutaneous nephrolithotomy (mPCNL) outcome. Methodology This descriptive retrospective analysis was carried out at the Urology Department, Lady Reading Hospital, Peshawar, Pakistan. Male and female patients in the age range of 18-70 years who underwent multiple tract mPCNL for renal stones from July 1, 2021, to June 30, 2023, were included in the analysis. Results  A total of 110 patients were registered. Stone-free status (SFS) was achieved in 78.2% (n=86), and complications were observed in 13.6% (n=15) patients. The odds ratio for STONE score, GSS, CROES scoring system, and RSCS for predicting the SFS was 7.093 (95%CI 2.40-20.89), 9.333 (95%CI 2.92-29.81), 11.70 (95%CI 2.56-53.38) and 3.450 (95%CI 1.25-9.53), respectively. Conclusion  Multiple tract mPCNL is a safe and effective technique for the management of renal stones, producing a high stone-free rate. This study demonstrated adequate efficacy and dependability of the four scoring systems in predicting SFS.

A comparison of S.T.O.N.E nephrolithometry scoring system, Guy's stone score, and Seoul National University Renal Stone Complexity (S-ReSC) in predicting mini-PCNL stone-free rate

The main goal of the study is to evaluate the three stone scoring systems (S.T.O.N.E nephrolithometry scoring system (STONE), Guy's stone score (GSS) and Seoul National University Renal Stone Complexity (S-ReSC)) for the stone-free rate (SFR) of mini-PCNL. We retrospectively analyzed 72 patients who received mini-PCNL from February 2018 to October 2020. The SFR, complication rates, hospitalization days and recurrence rates were analyzed using three stone scoring systems. The result showed statistical significance in the association between scoring system and stone-free (STONE: OR 95%CI 0.409 (0.221-0.759), p = 0.0045; S-ReSC OR 95%CI 0.633 (0.401-0.999), p = 0.0497), but not GSS (OR 95%CI 0.776 (0.397-1.516), p = 0.4581). After adjusting the potential confounding factors, the area under curve (AUC) of STONE, GSS, and S-ReSC was 0.86, 0.78, and 0.81, respectively, and Akaike information criterion (AIC) of STONE, GSS, and S-ReSC was 64.65, 74.89, and 69.92, respectively. The accuracy rate of STONE, GSS, and S-ReSC was 0.81, 0.75, and 0.79, respectively. There was no statistically difference of predicting stone recurrence (p = 0.46, 0.53, 0.86), complications (p = 0.74, 0.51, 0.16) and hospitalization days (p = 0.77, 0.86, 0.87) in STONE, GSS, and S-ReSC, respectively. In conclusion, both the STONE and S-ReSC stone scoring systems are viable for predicting the SFR following mini-PCNL, especially after variable adjustment with the STONE system demonstrating superiority over S-ReSC.

Design and internal validation of S.I.C.K.: a novel nomogram predicting infectious and hemorrhagic events after percutaneous nephrolithotomy

BACKGROUND

Hemorrhagic and infectious events represent severe complications after percutaneous nephrolithotomy (PCNLs). Existing nephrolithometric nomograms have been introduced but their reliability in predicting complications is debated. We present a newly designed nomogram with intention to predict hemorrhagic/infectious events after PCNLs.

METHODS

We conducted a multicentric prospective study on adult patients undergoing standard (24 Fr) or mini (18 Fr) PCNL. Dataset was derived from previous RCT, where patients have been assigned to mini-PCNL or standard-PCNL to treat renal stones up to 40 mm. Aim of the study was to identify preoperative risk factors for early postoperative infectious/hemorrhagic complications including fever, septic shock, transfusion or angioembolization.

RESULTS

A total of 1980 patients were finally included. 992 patients (50.1%) received mini-PCNL and 848 standard PCNL (49.9%). The overall SFR was 86.1% with a mean maximum stone diameter of 29 mm (SD 25.0-35.0). 178 patients (8.9%) had fever,14 (0.7%) urosepsis, 24 patients (1.2%) required transfusion and 18 (0.9%) angioembolization. The overall complication was (11.7%). After multivariable analysis, the included elements in the nomogram were age (P=0.041), BMI (P=0.018), maximum stone diameter (P<0.001), preoperative hemoglobin (P=0.005), type 1/2 diabetes (P=0.05), eGFR<30 (P=0.0032), hypertension (>135/85 mmHg, P=0.001), previous PCNL or pyelo/nephrolithotomy (P=0.0018), severe hydronephrosis (P=0.002). After internal validation, the AUC of the model was 0.73.

CONCLUSIONS

This is the first nomogram predicting infections and bleedings after PCNLs, it shows a good accuracy and can support clinicians in their patients' peri-operative workout and management.

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.

Stone-scoring systems for predicting complications in percutaneous nephrolithotomy: A systematic review of the literature

Objective

Percutaneous nephrolithotomy is a treatment of choice for larger stones of the upper urinary tract. Currently, several nephrolithometric nomograms for prediction of post-operative surgical outcomes have been proposed, although uncertainties still exist regarding their roles in the estimation of complications.

Methods

We conducted a systematic review on PubMed and Web of Sciences databases including English studies with at least 100 cases and published between January 2010 and December 2021. We identified original articles evaluating correlations between the Guy's stone score, the stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E) (S.T.O.N.E.), Clinical Research Office of the Endourological Society (CROES), and Seoul National University Renal Stone Complexity (S-ReSC) scores and post-operative complications in adult patients. We also included newly designed nomograms for prediction of specific complications.

Results

After an initial search of 549 abstracts, we finally included a total of 18 papers. Of them, 11 investigated traditional nephrolithometric nomograms, while seven newly designed nomograms were used to predict specific complications. Overall, 7316 patients have been involved. In total, 14 out of 18 papers are derived from retrospective single-center studies. Guy's stone score obtained correlation with complications in five, S.T.O.N.E. nephrolithometry score in four, while CROES score and S-ReSC score in three and two, respectively. None of the studies investigated minimally invasive percutaneous nephrolithotomy (PCNL) and all cases have been conducted in prone position. Considering newly designed nomograms, none of them is currently externally validated; five of them predict post-operative infections; the remaining two have been designed for thromboembolic events and urinary leakage.

Conclusion

This review presents all nomograms currently available in the PCNL field and highlights a certain number of concerns. Published data have appeared contradictory; more recent tools for prediction of post-operative complications are frequently based on small retrospective cohorts and lack external validations. Heterogeneity among studies has also been noticed. More rigorous validations are advisable in the future, involving larger prospective patients' series and with the comparison of different tools.

Reliability of nephrolithometric nomograms in patients treated with minimally invasive percutaneous nephrolithotomy: A precision study

Objectives

The study aimed to evaluate quality of nephrolithometric nomograms to predict stone-free rates (SFRs) and complication rates (CRs) in case of minimally invasive percutaneous nephrolithotomy (PNL). In the last decade, nomograms have been introduced to estimate the SFRs and CRs of PNL. However, no data are available regarding their reliability in case of utilization of miniaturized devices. Herein we present a prospective multicentric study to evaluate reliability of Guy's stone score (GSS), the stone size, tract length, obstruction, number of involved calyces, and essence of stone (S.T.O.N.E.) nephrolithometry score and Clinical Research Office of the Endourological Society (CROES) score in patients treated with minimally invasive PNL.

Methods

We evaluated SFRs and CRs of 222 adult patients treated with miniaturized PNL. Patients were considered stone-free if no residual fragments of any size at post-operative unenhanced computed tomography scan. Patients demographics, SFRs, and CRs were reported and analyzed. Performances of nomograms were evaluated with the area under the curve (AUC).

Results

We included 222 patients, the AUCs of GSS, CROES score, and S.T.O.N.E. nephrolithometry score were 0.69 (95% confidence interval [CI] 0.61-0.78), 0.64 (95% CI 0.56-0.73), and 0.62 (95% CI 0.52-0.71), respectively. Regarding SFRs, at multivariate binomial logistic regression, only the GSS had significance with an odds ratio of 0.53 (95% CI 0.31-0.95, p=0.04). We did not find significant correlation with complications, with only a trend for GSS.

Conclusion

This is the first study evaluating nomograms in miniaturized PNL. They still show good reliability; however, our data showed lower performances compared to standard PNL. We emphasize the need of further studies to confirm this trend. A dedicated nomogram for minimally invasive PNL may be necessary.

International Alliance of Urolithiasis (IAU) Guideline on percutaneous nephrolithotomy

The International Alliance of Urolithiasis (IAU) would like to release the latest guideline on percutaneous nephrolithotomy (PCNL) and to provide a clinical framework for surgeons performing PCNLs. These recommendations were collected and appraised from a systematic review and assessment of the literature covering all aspects of PCNLs from the PubMed database between January 1, 1976, and July 31, 2021. Each generated recommendation was graded using a modified GRADE methodology. The quality of the evidence was graded using a classification system modified from the Oxford Center for Evidence-Based Medicine Levels of Evidence. Forty-seven recommendations were summarized and graded, which covered the following issues, indications and contraindications, stone complexity evaluation, preoperative imaging, antibiotic strategy, management of antithrombotic therapy, anesthesia, position, puncture, tracts, dilation, lithotripsy, intraoperative evaluation of residual stones, exit strategy, postoperative imaging and stone-free status evaluation, complications. The present guideline on PCNL was the first in the IAU series of urolithiasis management guidelines. The recommendations, tips and tricks across the PCNL procedures would provide adequate guidance for urologists performing PCNLs to ensure safety and efficiency in PCNLs.

A novel nomogram and a simple scoring system for urinary leakage after percutaneous nephrolithotomy

Introduction:

The present study aimed to investigate the factors of prolonged urinary leakage (PUL) after percutaneous nephrolithotomy (PCNL) and develop a new and simple scoring system to predict it.

Patients and Methods:

We retrospectively reviewed patients with renal stones who underwent PCNL at the University of Health Sciences Izmir Bozyaka Training and Research Hospital between April 2011 and January 2020. The patients were divided into two groups according to the presence of PUL, and their preoperative and perioperative data were compared. A multivariate regression analysis was applied to examine the relationship between perioperative descriptors and PUL, and a nomogram was developed using significant predictors. Then, the individual components of the nomogram were assigned points to form a scoring system.

Results:

There were 92 and 840 patients in the groups with and without PUL, respectively. The results of the univariate logistic regression analysis showed that hydronephrosis grade, parenchymal thickness, duration of nephroscopy, and duration of nephrostomy catheter were significantly associated with PUL. Subsequently, a multivariate regression analysis was carried out with these four factors as possible independent risk factors of PUL after PCNL. Based on the results of this analysis, a nomogram prediction model was developed with an area under the curve value of 0.811, which was consequently used to develop a new simple score system consisting of three characteristics: parenchymal thickness (1–5 points), duration of nephroscopy (1–3 points), and hydronephrosis grade (1–3 points).

Conclusion:

A novel scoring system is a useful tool for predicting PUL in patients who have undergone percutaneous nephrolithotomy.

Application of S.T.O.N.E. Nephrolithometry Score for Prediction of Stone-Free Status and Complication Rates in Patients Who Underwent Percutaneous Nephrolitotomy for Renal Stone

Background: Renal stone disease is a common disorder in urology practice. Kidney stone has various treatment methods such as extracorporeal shock wave lithotripsy, retrograde intrarenal surgery, and percutaneous nephrolithotomy (PCNL). In this study, we aimed to determine the value of S.T.O.N.E. nephrolithometry score, which is considered as a new scoring system for predicting residual stone rate and complications in patients undergoing PCNL due to renal calculi. Materials and Methods: A total of 120 patients >18 years old who underwent PCNL were evaluated prospectively. Five parameters available from preoperative noncontrast-enhanced computed tomography were measured: stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E) and then S.T.O.N.E. nephrolithometry score was calculated. The prediction of the stone-free rates and complication rates of this scoring was evaluated statistically. Results: When the age, gender, body mass index, comorbidities, and American Society of Anesthesiologists scores of the patients were evaluated according to the patients' postoperative stone-free status, no statistical difference was found between the groups. Patients had a stone-free rate of 78%. Patients' mean neuropilitometry score was calculated to be 7.75 S.T.O.N.E. nephrolithometry score statistically significant (P = .001) for prediction of stone-free status. S.T.O.N.E. nephrolithometry score was significantly correlated with operation time, estimated blood loss, duration of fluoroscopy, duration of hospital stay, and number of punctures. Complications were seen in 13 patients. Conclusions: S.T.O.N.E. nephrolithometry score can be used as an objective criterion for predicting the complexity of the PCNL process. In addition, this scoring system is expected to provide more objective preoperative counseling and can provide standardization in academic studies.

Evaluation of various nephrometric scoring system for nephrolithiasis to predict stone free status after percutaneous nephrolithotomy: A comparative study

BACKGROUND

The CROES Nephrolithometry nomogram, S.T.O.N.E. Nephrolithometry Score and Guy's stone score were introduced for stratification of kidney stones disease on the basis of quantitative stone burden and its distribution. Till date there has been very limited data on head to head comparison of the existing scoring systems. Comparison and analyses among the scoring system helps in further refinement of these systems along with development of new more effective and broadly acceptable nomogram.

OBJECTIVE

Predictability of the stone-free status (SFS) and post-operative complication after PCNL by various scoring systems (The CROES nomogram, S.T.O.N.E. nephrolithometry score and Guy's stone score).

MATERIALS AND METHODS

Total 100 adult patients underwent PCNL after considering inclusion and exclusion criteria. All patients underwent Preoperative NCCT scan, investigations of blood (Hb%, PCV, bleeding and coagulation profile, urea, and creatinine), and urine (RE/ME and C/S), Postoperative X ray KUB/NCCT.

RESULTS

ROC curves were developed for each scoring system to determine the accuracy to predict stone free status. We found CS had significantly higher AUC than other scoring systems [p-value for CS vs GSS = 0.0091 & CS vs SS = 0.000]. So CS has higher accuracy to predict stone free status. None of the scoring system had shown significantly higher AUC than other scoring system in predicting complication.

CONCLUSION

CROES Nephrolithometry nomogram is most accurate to predict preoperative stone-free rate. All scoring systems can equally predict perioperative complications and other variables.

Development and validation of a simple stone score to estimate the probability of residual stones prior to percutaneous nephrolithotomy

BACKGROUND

The aim of the present study was to develop and internally validate a simple stone score (SSS) to estimate the probability of clinically significant residual fragments (CSRF) prior to percutaneous nephrolithotomy (PNL).

METHODS

The files of 1170 PNL procedures between January and December 2015 were evaluated. CT-derived stone characteristics were examined. Caliceal stone distribution (CSD) was assigned three grades based on the number of calices involved regardless of the renal pelvis (I = no or single calix; II = more than one calix; and III = more than 2 calices or complete staghorn stones). CSRF was defined as any residuals >4 mm in postoperative CT. A logistic regression model to predict the CSRF was fitted, and coefficients were used to develop the SSS. The SSS was validated by discrimination, calibration, and decision curve analysis (DCA).

RESULTS

Patients' data were split into training (936, 80%) and validating (234, 20%) datasets. In the training partition, independent predictors of CSRF were CSD-grade II (OR: 4.2; 95%CI: 2.5-7; P<0.001), grade III (OR: 7.8; 95%CI: 4.2-14.4; P<0.001) and largest stone diameter (LSD) (OR:1.3; 95%CI: 1.1-1.6; P<0.001). Score points 0, 1, 2, and 0, 3, 9 were given to LSD<30, 30-40, >40 mm, and CSD grades I, II, III, respectively. Discrimination of the SSS was 0.79 and after 10-fold cross-validation and internal validation was 0.86. The calibration plot and DCA highlighted the validity and clinical significance of the SSS.

CONCLUSIONS

The novel SSS could be used to describe the risk of CSRF prior to PNL. Further studies are invited for external validation.

Investigation of Factors Related to Percutaneous Nephrolithotomy Failure in Horseshoe Kidneys and Comparison of Three Stone Scoring Systems in Prediction of Outcomes

INTRODUCTION

We aimed to identify factors affecting percutaneous nephrolithotomy (PNL) outcomes among patients with horseshoe kidney (HSK) and assess the predictive accuracy of the Clinical Research Office of the Endourological Society (CROES), Guy's Stone Score (GSS), and S.T.O.N.E. scoring systems.

METHODS

Data from 98 patients with HSK who underwent PNL between November 2010 and January 2020 were evaluated. Patients were divided into the stone-free (SF) and non-SF groups and compared according to demographic data, stone and surgical characteristics, and stone scoring systems. Multivariate logistic regression analysis was performed to identify factors associated with SF status.

RESULTS

Among the included patients, 87 were male and 11 were female (mean age: 47.37 ± 14.42 years). The SF rate was 84.7% (83 patients). Group analysis identified GSS (p < 0.001), CROES score (p < 0.001), S.T.O.N.E. score (p = 0.014), stone burden (p = 0.045), and multiplicity (p < 0.001) as factors associated with SF status. Among our cohort, 10 patients developed complications. All scoring systems were significantly correlated with SF status (CROES: r = -0.442, p < 0.001; GSS: r = 0.442, p < 0.001; S.T.O.N.E.: r = 0.250, p = 0.013), while CROES score was identified as an independent factor associated with SF status (95% CI: 0.937-0.987; p = 0.003).

CONCLUSIONS

PNL is an effective method for treating nephrolithiasis among patients with HSK. Moreover, stone-related factors, such as larger size, multiplicity, and complexity, were associated with procedural failure. Finally, the CROES nomogram was a better predictor of SF status compared with other scoring systems.

Percutaneous Nephrolithotomy with Intraoperative Computed Tomography Scanning Improves Stone-Free Rates

Introduction: The use of fluoroscopy during percutaneous nephrolithotomy (PCNL) may lead to an overestimation of stone-free rates. The objective of this study is to demonstrate the feasibility of intraoperative CT-guided PCNL compared with standard of care (SoC) PCNL. Patients and Methods: A prospective feasibility study (20 patients undergoing PCNL with an intraoperative CT scan between June 2017 and February 2020) and a retrospective study of a historical cohort (20 consecutive patients undergoing SoC PCNL between September 2015 and September 2016) were conducted. All procedures were performed by an expert endourologist in a tertiary referral hospital. Follow-up was performed at 6 weeks postoperatively. The primary goal is to investigate the practicality and potential benefits and harms of intraoperative CT scanning during PCNL. Secondary outcomes are a stone-free rate after the 6-week follow-up, perioperative radiation exposure, the need for postoperative imaging, and peri- and postoperative complications. Statistical significance was considered at p < 0.05. Results: The initial stone-free rate in the CT scan group was 65% (n = 13). In 25% (n = 5) of patients, residual stone fragments were removed after the perioperative CT scan. In the SoC group, 85% (n = 17) of patients were thought to be stone free perioperatively. At the 6-week follow-up, 80% (n = 16) in the CT scan group vs 50% in the SoC group (n = 10) were found to be stone free. Radiation exposure, perioperatively, was higher in the CT scan group. Complications were comparable between groups. Limitations of the study are the nonrandomized design of the study and nonstandardized follow-up imaging. Conclusions: Intraoperative CT scanning during PCNL is feasible and gives a better estimate of any remaining stone fragments compared with fluoroscopy only.

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.

Preoperative risk factors for complications of percutaneous nephrolithotomy

This study was conducted to evaluate preoperative risk factors for development of complications of percutaneous nephrolithotomy (PCNL). All consecutive patients aged ≥ 16 years who underwent PCNL during 2015 were retrospectively reviewed. Non-contrast CT (NCCT) was performed for all patients to evaluate stone complexity. The technique of PCNL was the same for all patients. Intra-operative and postoperative complications were recorded and classified based on modified Clavien system. The differences in preoperative data (patients, renal and stone characteristics including Guy's and STONE scores) between complicated and uncomplicated cases were compared using univariate and multivariate statistical analyses for detection of independent risk factors. The study included 1178 patients (61% were males). Mean age was 50 ± 12 years, and mean BMI was 30.7 ± 5.7 kg/m². Complicated group included 166 patients (14.1%). Independent risk factors on multivariate analysis were infected preoperative urine culture (RR: 2.098, P 0.001, 95%CI: 1.380-3.189), largest stones diameter 30 mm or more (RR: 2.481, P > 0.001, 95%CI: 1.697-3.627) and number of calyces affected by the stones (RR: 2.431, P 0.002, 95%CI: 1.400-4.222 for affection of two calyces and RR: 2.778, P 0.005, 95%CI: 1.357-5.684 for affection of three calyces). While two scoring systems (Guy's and STONE) were not predictive of complications after PCNL, preoperative risk factors were infected preoperative urine culture, distribution of the stones or stone branches in two or three calyceal groups and stone size 30 mm or more.

Guy's Stone Score as a Predictor for Stone-Free Rate and Complications in Percutaneous Nephrolithotomy: A Single-Center Report from a Stone Belt Country

OBJECTIVES

To evaluate Guy's Stone Score (GSS) as a grading system for the complexity of renal calculi before percutaneous nephrolithotomy (PCNL) and as a predictor for stone-free rate (SFR) and potential complications in the setting of a developing country with many cases of advanced complex stone disease.

PATIENTS AND METHODS

We performed a prospective study on 115 patients with renal stones who had PCNL between August 2017 and October 2018. Stone complexity was classified according to GSS using preoperative imaging. The rates of perioperative complications were assessed using the Clavien grading system, and the SFR was assessed in the 3rd postoperative week by abdominal X-ray and renal ultrasound. The χ2 and one-way ANOVA tests were used for statistical analysis. A p value ≤0.05 was considered significant.

RESULTS

The study included 115 patients (77 males) with a mean age of 50.2 (±13.3) years. Cases were classified according to GSS into 4 grades; there were 24 (20.9%) grade I, 48 (41.7%) grade II, 25 (21.7%) grade III, and 18 (15.7%) grade IV cases. There was a significant inverse correlation between GSS grade and SFR (p < 0.001). The rate of complications using the Clavien grading system were significantly higher in GSS grades III and IV (p = 0.002). So were the rates of blood transfusion, the need for >1 access tract, and the duration of hospitalization.

CONCLUSION

GSS is a simple and easily reproducible system to classify the complexity of renal stones. In our setting, it also proved an excellent tool to predict SFR, perioperative complications, and associated ancillary procedures. Ultimately, it can help surgeons and, above all, patients to make a more informed decision about their surgery.

Morphometry scores: Clinical implications in the management of staghorn calculi

Due to their large size, rapid growth, and attendant morbidity, staghorn calculi are complex clinical entities that impose significant treatment-related challenges. Moreover, their relative heterogeneity-in terms of both total stone burden and anatomic distribution-limits the ability to standardize their characterization and the reporting of surgical outcomes. Several morphometry systems currently exist to define the volumetric distribution of renal stones, in general, and to predict the outcomes of percutaneous nephrolithotomy; however, they fall short in their applicability to staghorn stones. In this review, we aim to discuss the clinical utility of morphometry systems and the influence of pelvicalyceal anatomy on the management of these complex calculi.

Predicting the Postoperative Outcome of Percutaneous Nephrolithotomy with Machine Learning System: Software Validation and Comparative Analysis with Guy's Stone Score and the CROES Nomogram

Purpose: To validate the output of a machine learning-based software as an intelligible interface for predicting multiple outcomes after percutaneous nephrolithotomy (PCNL). We compared the performance of this system with Guy's stone score (GSS) and the Clinical Research Office of Endourological Society (CROES) nomogram. Patients and Methods: Data from 146 adult patients (87 males, 59%) who underwent PCNL at our institute were used. To validate the system, accuracy of the software for predicting each postoperative outcome was compared with the actual outcome. Similarly, preoperative data were analyzed with GSS and CROES nomograms to determine stone-free status as predicted by these nomograms. A receiver operating characteristic (ROC) curve was generated for each scoring system, and the area under the ROC curve (AUC) was calculated and used to assess the predictive performance of all three models. Results: Overall stone-free rate was 72.6% (106/146). Forty of 146 patients (27.4%) were scheduled for 42 ancillary procedures (extracorporeal shockwave lithotripsy [SWL] [n = 31] or repeat PCNL [n = 11]) to manage residual renal stones. Overall, the machine learning system predicted the PCNL outcomes with an accuracy ranging between 80% and 95.1%. For predicting the stone-free status, the AUC for the software (0.915) was significantly larger than the AUC for GSS (0.615) or CROES nomograms (0.621) (p < 0.001). Conclusion: At the internal institutional level, the machine learning-based software was a promising tool for recording, processing, and predicting outcomes after PCNL. Validation of this system against an external dataset is highly recommended before its widespread application.

Inter-observer variability amongst surgeons and radiologists in assessment of Guy's Stone Score and S.T.O.N.E. nephrolithometry score: A prospective evaluation

Objective

(a) To assess the inter-observer variability amongst surgeons performing percutaneous nephrolithotomy (PCNL) and radiologists for the Guy’s Stone Score (GSS) and S.T.O.N.E. (stone size [S], tract length [T], obstruction [O], number of involved calyces [N], and essence or stone density [E]) nephrolithometry score; (b) To determine which scoring system of the two is better for predicting the stone-free rate (SFR) after PCNL.

Patients, subjects and methods

Patients undergoing PCNL between February 2016 and September 2016 were prospectively enrolled. Preoperative computed tomography was done in all patients. The GSS and S.T.O.N.E. nephrolithometry score were independently calculated by eight surgeons and four radiologists. The patients were operated on by one of the surgeons (all were consultants). The Fleiss’ κ coefficient was used to assess agreement independently between the surgeons and radiologists. Receiver operating characteristic (ROC) curves were constructed for predicting the SFR using the average of the scores of the surgeons and radiologists separately.

Results

A total of 157 patients underwent PCNL. The SFR was 71.3% (112/157 patients). The Fleiss’ κ scores ranged from 0.51 to 0.88 (overall 0.79) for the S.T.O.N.E. score and 0.53–0.91 for the GSS, suggesting moderate to very good agreement. The ROC curve for the S.T.O.N.E. nephrolithometry scores of surgeons (area under the curve [AUC] = 0.806) as well as the radiologists (AUC = 0.810) had a higher predictive value for the SFR than the GSS of the surgeons (AUC = 0.738) and the radiologists (AUC = 0.747).

Conclusion

There is overall good agreement between surgeons and radiologists for both the GSS and S.T.O.N.E. nephrolithometry score. The S.T.O.N.E. score had a higher predictive value for the SFR than the GSS.

Abbreviations

AUC: area under the curve; GSS: Guy’s Stone Score; KUB: kidneys, ureters and bladder; NCCT: non-contrast CT; PCNL: Percutaneous nephrolithotomy; ROC: receiver operating characteristic; SFR: stone-free rate; S.T.O.N.E.: stone size [S], tract length [T], obstruction [O], number of involved calyces [N], and essence or stone density [E]

Evaluation of three stone-scoring systems for predicting SFR and complications after percutaneous nephrolithotomy: a systematic review and meta-analysis

Background

Clinical studies assessing the feasibility and accuracy of three stone scoring systems’s (SSSs: Guy’s stone score, CROES nomogram and S.T.O.N.E nephrolithometry scoring system) have reported contradictory outcomes. This systematic evaluation was performed to obtain comprehensive evidence with regard to the feasibility and accuracy of three SSSs.

Methods

A systematic search of Embase, Pubmed, Medline, and the Cochrane Library was conducted to identify studies that compared three SSSs up to Mar 2018. Patients were categorized according to stone free (SF) and no-stone free (NSF), Outcomes of interest included perioperative variables, stone-free rate (SFR), and complications.

Results

Ten studies estimating three SSSs were included for meta-analysis. The results showed that SF patients had a significantly lower proportion of male (OR = 1.48, P = 0.0007), lower stone burden (WMD = -504.28, P < 0.0001), fewer No of involved calyces (OR = -1.23, P = 0.0007) and lower proportion of staghorn stone (OR = 0.33, P < 0.0001). Moreover, SF patients had significantly lower score of Guy score (WMD = -0.64, P < 0.0001), but, S.T.O.N.E. score (WMD = -1.23, P < 0.0001) and a higher score of CROES nomogram (WMD = 29.48, P = 0.003). However, the comparison of area under curves (AUC) of predicting SFR indicated that there was no remarkable difference between three SSSs. Nonetheless, Guy score was the only stone scoring system that predicted complications after PCNL (WMD = -0.29, 95% CI: − 0.57 to − 0.02, P = 0.03).

Conclusions

Our meta-analysis indicated that the three SSSs were equally, feasible and accurate for predicting SFR after PCNL. However, Guy score was the only stone scoring system that predicted complications after PCNL.

Electronic supplementary material

The online version of this article (10.1186/s12894-019-0488-y) contains supplementary material, which is available to authorized users.

Comparison of Scoring Systems in Predicting Success of Percutaneous Nephrolithotomy

Background:

Scoring systems are useful to inform the patients about the success and complication rates of the operation prior the surgery.

Aims:

To determine the applicability of the popular scoring systems (Guy’s, stone size, tract length, obstruction, number of involved calices, and essence/stone density and Clinical Research Office of the Endourological Society) by means of examining preoperative data of patients treated with percutaneous nephrolithotomy.

Study Design:

Cross sectional study.

Methods:

We retrospectively reviewed files of the patients who had undergone percutaneous nephrolithotomy in our center between 2011 and 2015. Excluded from the study were patients aged <18 years, and those who were not assessed preoperatively with computed tomography. Preoperative computed tomography images of all patients were assessed by a single observer, and patients were graded based on three scoring system. Demographic data were analyzed along with perioperative data (operation, fluoroscopy, length of hospital stay, changes in hematocrit values, location, and number of access sites, stone-free and complication rates).

Results:

A total of 298 patients who had been treated with 300 procedures were enrolled into the study. Mean age, stone burden, number of stones, and density were 48.1±12.9 years, 663.5±442.8 mm², 1.8±1.1 and 888.3±273 HU respectively. Scores of the cases based on Guy’s, stone size, tract length, obstruction, number of involved calices, and essence/stone density, and Clinical Research Office of the Endourological Society scoring system were calculated as 2, 7.6, and 222.1 points respectively. 81.6% of the patients were stone-free. Complications were detected in 30 (9.9%) patients. Based on receiver operating characteristic curve analysis a positive correlation was detected between success rate and scoring systems, i.e., Guy’s (p=<0.001, r=-0.309), stone size, tract length, obstruction, number of involved calices, and essence/stone density (p=<0.001, r=-0.295), and Clinical Research Office of the Endourological Society (p=<0.001, r=0.426). The Clinical Research Office of the Endourological Society scoring system had the highest predictive value. The sensitivity rates rates for Guy’s, Clinical Research Office of the Endourological Society and Stone scoring system were as 78.78%, 80% and 82.34% respectively.

Conclusion:

All of scoring systems predicted correctly the success of the percutaneous nephrolithotomy procedures. The Clinical Research Office of the Endourological Society scoring system had the highest predictive value.

Predictive ability of Guy's stone score in pediatric patients undergoing percutaneous nephrolithotomy

BACKGROUND

Several authors have evaluated, in a number of external validation and predominantly adult studies, Guy's stone score (GSS) as a predictive tool for the assessment of stone clearance after percutaneous nephrolithotomy (PCNL). However, there are limited and conflicting data investigating whether GSS could be a potential independent factor associated with residual stone rates and complications of PCNL for children.

OBJECTIVE

The aim of the current study was to evaluate the ability of GSS, as an independent factor, to predict residual stone rates and complications in pediatric patients undergoing PCNL.

STUDY DESIGN

The records of the pediatric patients who had undergone PCNL for stone disease at the current department were retrospectively reviewed. Variables included patient, stone, and treatment parameters. The GSS was used for assessment of stone complexity. Univariate and multivariate analyses were performed to evaluate factors associated with residual stone rates and complications of pediatric PCNL.

RESULTS

The study group consisted of 114 children (63 boys and 51 girls) with a median (interquartile range) age of 6 (3-11) years and who had undergone 122 PCNLs (eight bilateral). Multivariate logistic regression analysis (Summary Table) demonstrated that the independent risk factors for increased residual stone rate following pediatric PCNL monotherapy were GSS (OR 3.14, 95% CI 1.31-7.49, P = 0.01) and number of calyces involved (OR 4.02, 95% CI 1.11-14.53, P = 0.033). Multivariate logistic regression analysis demonstrated that the independent risk factors for complications following pediatric PCNL were surgical experience (OR 2.72, 95% CI 1.09-6.82, P = 0.032), and operation time (OR 1.01, 95% CI 1.00-1.03, P = 0.040).

DISCUSSION

A prediction model is needed to pre-operatively counsel patients and evaluate outcomes for measuring treatment success of PCNL. The GSS provides a simple, reliable and reproducible tool for describing the complexity of PCNL while predicting postoperative stone-free status, despite its limitations. However, little research has been conducted on the applicability of GSS in pediatric patients undergoing PCNL. In addition, conflicting results have been reported about its association with complications of pediatric PCNL.

CONCLUSIONS

The current study found that although GSS had a significant predictive ability for residual stone rates after pediatric PCNL revealed by multivariate logistic regression, the results did not conclude that complexity of GSS was directly proportional to complications of pediatric PCNL. The factors, including calyceal involvement and surgeon experience, may need to be incorporated in GSS to further improve its ability to predict outcomes of pediatric PCNL.

IRB APPROVED PROTOCOL NUMBER

1422.

Predictability and Practicality of Image-Based Scoring Systems for Patient Assessment and Outcome Stratification During Percutaneous Nephrolithotomy: a Contemporary Update

Preoperative nomograms offer systematic and quantitative methods to assess patient- and stone-related characteristics and their impact on successful treatment and potential risk of complication. Discrepancies in the correlation of perioperative variables to patient outcomes have led to the individual development, validation, and application of four independent scoring systems for the percutaneous nephrolithotomy: Guy's stone score, S.T.O.N.E. nephrolithometry, Clinical Research Office of the Endourology Society nomogram, and Seoul National University Renal Stone Complexity. The optimal nomogram should have high predictive ability, be practically integrated into clinical use, and be widely applicable to urinary stone disease. Herein, we seek to provide a contemporary evaluation of the advantages, disadvantages, and commonalities of each scoring system. While the current data is insufficient to conclude which scoring system is destined to become the gold standard, it is crucial that a nephrolithometric scoring system be incorporated into common practice to improve surgical planning, patient counseling, and outcome assessment.

Comparison of STONE, CROES and Guy's nephrolithometry scoring systems for predicting stone-free status and complication rates after percutaneous nephrolithotomy in obese patients

In this study, we aim to evaluate the accuracy of STONE (stone size, tract length, obstruction, number of involved calyces, and essence/stone density), Clinical Research Office of the Endourological Society (CROES), and Guy's nephrolithometry scoring systems (NSS) in obese patients. The charts of patients who underwent percutaneous nephrolithotomy (PNL) between June 2008 and June 2016 were retrospectively analyzed. Calculations of the STONE, CROES, and Guy's NSS were performed by a resident who was well informed regarding each NSS. Patients were classified under nine scores according to STONE, four grades according to CROES, and four grades according to Guy's NSS. In total, 248 obese patients were enrolled in the study. Stone size was significantly higher in patients without stone-free status (p = 0.001). In patients who were stone-free and those with residual stones, the mean STONE score was 9.71 and 9.23 (p = 0.160), CROES was 172 and 129 (p = 0.001), and Guy's NSS was 1.67 and 2.75 (p = 0.001). Multivariate regression analysis identified the CROES and Guy's NSS were independent factors for PNL success in obese patients (p = 0.01 and p = 0.01, respectively). The CROES and Guy's NSS showed good accuracy with PNL success (AUC = 0.777 and AUC = 0.844, respectively). None of the three NSS systems were statically associated with a complication rate (p = 0.23 for STONE, p = 0.14 for CROES, and p = 0.51 for Guy's NSS). Our study demonstrated that CROES and Guy's NSS were independent predictors of stone-free rate following PNL in obese patients. Our study also revealed that three of the NSSs were not useful for predicting PNL complications in obese patients.

Comparison of CROES, S.T.O.N.E, and Guy's scoring systems for the prediction of stone-free status and complication rates following percutaneous nephrolithotomy in patients with chronic kidney disease

PURPOSE

To evaluate and compare the accuracy of S.T.O.N.E, Clinical Research Office of the Endourological Society (CROES), and Guy's stone score in patients with chronic kidney disease (CKD) following percutaneous nephrolithotomy (PNL).

METHODS

The charts of patients who had undergone a prone percutaneous nephrolithotomy from June 2006 to June 2016 were retrospectively analyzed. Patients accepted as stage 3 and higher according to chronic kidney disease epidemiology collaboration formula, were enrolled into the study. Calculation of the CROES, S.T.O.N.E, and Guy's scoring system (SS) was made as defined in original papers. Patients were categorized into four scores according to CROES, into nine scores according to S.T.O.N.E, and into four scores according to Guy's SS.

RESULTS

A total of 303 patients fulfilled the study inclusion criteria. The mean preoperative eGFR and creatinine levels were 47 mL/min and 1.55 mg/dL, respectively. In patients who were stone free and those with residual stones, the mean CROES SS was 179 and 137 (p < 0.001), the mean S.T.O.N.E score was 8.8 and 9.9 (p < 0.001), and the mean Guy's SS was 1.8 and 2.4 (p < 0.001), respectively. Multivariate regression analysis revealed CROES SS was the only scoring system, which had a predictive value for PNL outcome in patients with CKD (p = 0.011) and any of three SS were not useful for predicting PNL complications in patients with CKD.

CONCLUSION

Our study demonstrated the CROES SS was the only independent factor in the prediction of PNL outcome in CKD patients. Furthermore, three of the NSSs were not useful for predicting PNL complications in patients with CKD.

Current clinical scoring systems of percutaneous nephrolithotomy outcomes

Percutaneous nephrolithotomy has become the preferred treatment modality for patients with large renal calculi. The technique provides excellent stone clearance, but complication rates are higher than those of minimally invasive techniques, such as ureteroscopy and shockwave lithotripsy. Guy's stone score, S.T.O.N.E. nephrolithometry, the CROES nomogram, and S-ReSC are contemporary scoring systems introduced to provide standardized grading of stone complexity and outcomes of percutaneous stone surgery. Guy's stone score is easy to apply and has been validated in multiple studies. The S.T.O.N.E. score is based on factors determined through CT imaging, which is the currently preferred imaging modality for patients with nephrolithiasis. The CROES nomogram was developed from data in a large multicentre database and has high statistical power. Determination of the S-ReSC score relies on stone location only, providing a simple approach to grading disease complexity. Each system has advantages and disadvantages, but several studies suggest that their ability to predict stone-free rate is comparable. The optimal system should have a high predictive ability, should be simple to use and should be widely applicable. Additional studies are required to evaluate patient clinical factors that influence stone complexity and are predictive of outcomes. A future unified scoring system might incorporate the strengths of each currently available system and optimize care of patients with nephrolithiasis.

Comparison of Guy’s vs S.T.O.N.E. nephrolithometry scoring systems in predicting the success rate of PCNL

Introduction and objective:

The aim of the present study was to compare the accuracy of the Guy’s and S.T.O.N.E. scoring systems in predicting percutaneous nephrolithotomy (PCNL) outcomes.

Methods:

This prospective study was carried out in the Department of Urology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, between August 2013 and September 2015 in collaboration with the Department of Radiodiagnosis and Imaging. A total of 100 cases of renal calculi operated on with PCNL were considered in the study on the basis of CT morphodensitometry. The study was approved by the institute’s ethical committee. Guy’s and S.T.O.N.E. scoring systems were calculated. Regression analysis and ROC curves were performed.

Results:

A total of 100 PCNLs were operated on. The overall stone-free rate was 90% with a complication rate of 17%. When compared to patients with residual fragments, stone-free patients had significantly lower Guy’s grade (3.5 vs 2; p < 0.001) and S.T.O.N.E. score (9.1 vs 7.5; p = 0.023). Logistic regression analysis showed that both Guy’s and S.T.O.N.E. systems were significantly associated with stone-free status, OR 0.96 ( p < 0.001) and OR 0.94 ( p < 0.001), respectively. Furthermore, both scoring systems were significantly associated with estimated blood loss ( p = 0.02 and p = 0.004). There was good correlation between both scoring systems and operative time ( r = 0.2, p < 0.002 and r = 0.3, p < 0.002) and length of hospital stay ( r = 0.1, p = 0.002 and r = 0.2, p < 0.002). There were significant associations between both scoring systems and complications ( p < 0.001 and p = 0.004). There was no significant difference in the areas under the curves for the Guy’s and S.T.O.N.E. scoring systems (0.96 (95% CI 0.92–0.99) vs 0.94 (95% CI 0.89–1.001); p < 0.001).

Conclusion:

Both Guy’s and S.T.O.N.E scoring systems have comparable accuracies in predicting post-PCNL stone-free status. Other factors not included in either scoring system may need to be incorporated in the future to increase their accuracy.

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.

Interobserver Reliability and Reproducibility of the Clinical Research Office of the Endourological Society Nomogram in Predicting Percutaneous Nephrolithotomy Results

OBJECTIVE

To assess interobserver reliability and reproducibility of the Clinical Research Office of the Endourological Society (CROES) nephrolithometric nomogram.

PATIENTS AND METHODS

Preoperative data and postoperative outcomes of 100 consecutive patients who underwent percutaneous nephrolithotomy were obtained. Patients' data were reviewed separately by 4 independent urologists of different academic level: an experienced attending endourologist, a graduated fellow, a young fellow, and a resident. Each rater adjusted a CROES score in all 100 patients. Interobserver reliability was analyzed by assessing intraclass correlation (ICC) and kappa coefficient among and between all different raters.

RESULTS

Assessment of interobserver reliability showed good or excellent agreement among all raters. Moderate agreement was only found between the raters for the "presence of staghorn" score. ICCs among all raters expressed excellent levels for each independent CROES parameter and reached great statistical significance. The highest correlation was noticed for "stone burden" in contrast to "presence of staghorn" parameter that showed the lowest. ICC for the final CROES score revealed good to excellent agreement among all raters and all pairs of raters.

CONCLUSION

CROES nephrolithometry is a reproducible nomogram. Reproducible results were obtained within a single institution by multiple reviewers of varying experience within a short period of time after undergoing standardized training.