Prediction of Pediatric Percutaneous Nephrolithotomy Outcomes Using Contemporary Scoring Systems

Validation of stone-kidney size score to predict outcome and complications of pediatric percutaneous nephrolithotomy

INTRODUCTION

The prevelance of urinary system stone disease in children is emphasizing the need for minimally invasive treatments to decrease morbidity and recurrence risk. Percutaneous nephrolithotomy (PCNL) has emerged as a preferred approach for pediatric patients with complex stones due to its minimally invasive nature, including miniaturized and vacuum-assisted access sheaths, advanced laser technology and tubeless and outpatient procedures. However, adult scoring systems have proven ineffective in predicting success and complications in pediatric PCNL. This highlights the need for specialized scoring systems, such as the Stone-Kidney Size (SKS) scoring system, tailored to pediatric patients and will be evaluated in our study for its association with the stone-free rate (SFR) and complications.

MATERIALS AND METHODS

The data of 144 patients aged <17 years who had undergone PCNL between January 2008 and December 2019 were evaluated retrospectively. Demographics, stone characteristics, perioperative/postoperative outcomes were recorded for each patient. The SKS scoring system comprises the stone kidney index (SKI) and the number of stones, assigns one or two points based on single or multiple stones and an SKI value of <0.3 or ≥0.3, respectively. The SKI is computed by dividing the stone's longest axis by the kidney's longest axis. Residual stones less than 4 mm on non-contrast computed tomography are considered clinically insignificant residual fragments (CIRFs). Stone-free and CIRF patients were considered successful results. The relationship between the SKS scoring system and SFR, success, and complication rates after surgery was investigated. Statistical analyses were conducted using SPSS 22.0 software.

RESULTS

The SFR was 67.36% and 74.31% when CIRF patients were included, respectively, with a complication rate of 27%. In multivariate analysis, stone treatment history, stone burden, and SKS score were statistically significantly associated with SFR (p < 0.001, p = 0.032, p < 0.001, respectively). Furthermore, the SKS score was the only variable that showed a statistically significant relationship with success. No significant association was found between SKS score and complications (p = 0.342).

DISCUSSION

Our study demonstrates a relationship between the SKS scoring system and SFR in pediatric PCNL patients. However, shortcomings have been observed in its capacity to accurately predict post-PCNL complications. Despite being a retrospective analysis and having a single-center design, our study externally validates the relationship between the SKS scoring system and SFR after pediatric PCNL.

CONCLUSIONS

The SKS scoring system is associated with SFR in pediatric patients undergoing PCNL; however, this relationship has not been established for complications.

Prediction of percutaneous nephrolithotomy outcomes and flexible ureteroscopy outcomes using nephrolithometry scoring systems

BACKGROUND

Kidney stones account for a high proportion of urological emergencies. The main objective of this paper is to evaluate the predictive ability of five scoring systems for overall stone-free status and postoperative complications after percutaneous nephrolithotomy and retrograde ureteroscopy.

MATERIALS AND METHODS

This study retrospectively analysed 312 cases of kidney stone patients between January 2021 and May 2022 at our centre. Multivariate logistic regression as well as ROC curves were applied to determine the ability to evaluate each scale to predict stone-free rates and postoperative complications.

RESULTS

179 patients have undergone PCNL. After multivariate logistic regression, the S.T.O.N.E score and history of ipsilateral renal surgery were predictive of stone-free status, and the predictive power of the S.T.O.N.E score was higher than that of history of ipsilateral renal surgery. Grade 1 complications were considered to be related to Guy's score and grade 2 complications were considered to be related to history of diabetes mellitus. 133 patients have undergone f-URS. After multivariate logistic regression analysis, the modified S-ReSC score, RUSS score, and R.I.R.S score were predictive of stone-free status, with the R.I.R.S score being the strongest predictor. Evidence of grade 2 complications was considered to be related to abnormal renal function.

CONCLUSION

For PCNL, the S.T.O.N.E score had the best efficacy in predicting stone-free status, and the Guy's score had the best efficacy in predicting postoperative complications; for f-URS, the R.I.R.S score had the best efficacy in predicting stone-free status, and no scoring system predicted postoperative complications.

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.

Current status of nomograms and scoring systems in paediatric endourology: A systematic review of literature

INTRODUCTION

The incidence of paediatric kidney stone disease is increasing worldwide, with the requirement for endourological interventions mirroring this. Multiple nomograms, grading tools and scoring systems now exist in the adult setting, which aim to enhance the pre-operative planning and decision-making associated with these surgeries. In recent years, there has been increasing interest in nomograms dedicated for use in the paediatric setting. This study provides an up-to-date review and assessment of available paediatric endourology nomograms and scoring systems.

METHODS

A comprehensive search of worldwide literature was conducted according PRISMA methodology. Studies describing paediatric-specific endourology nomograms, scoring systems or grading tools and studies externally validating these tools, or existing adult tools in a paediatric population, were evaluated and included in the narrative data synthesis.

RESULTS

A total of 7 endourology nomograms were identified. 4 were paediatric-specific, 2 for shockwave lithotripsy, 1 for percutaneous nephrolithotomy or ureteroscopy and 1 for percutaneous nephrolithotomy specifically. Only the 2 shockwave lithotripsy nomograms have been externally validated in 4 further studies and showed efficacy in predicting treatment success. 3 adult tools, all specific to PCNL have been investigated and validated in a paediatric setting in 11 studies. In general, they showed efficacy in the prediction of stone free rate but were poor at predicting likelihood of complications.

CONCLUSION

A limited number of paediatric-specific endourology predictive nomograms are available to aid in the management of kidney stone disease, with the strongest evidence supporting those designed for shockwave lithotripsy. Although 3 adult tools have been implemented, there are problems applying these to the paediatric setting and further development of paediatric-specific tools is necessary.

A systematic review of nomograms used in urolithiasis practice to predict clinical outcomes in paediatric patients

INTRODUCTION

Nomograms, used to predict the risk and success of treatment of urinary tract stones, are being used in paediatric clinical practice. However, no studies have determined the best prediction model. This study aimed to identify the most robust nomogram(s) for predicting clinically relevant outcomes in urinary stone disease in paediatric patients.

METHODS

The EMBASE, MEDLINE, Cochrane Systematic Reviews, and Cochrane Central Register of Controlled Trials via Ovid were searched for publications on May 13, 2021. No study design and publication year limitations were applied. The risk of bias in the included studies was determined using PROBAST.

RESULTS

The review included fourteen studies, involving 3888 paediatric patients. We identified seven prognostic stone nomograms (Dogan, Onal, CMUN, SKS, Guy's stone score, S.T.O.N.E and CROES) that were validated for use in paediatric patients. Both Dogan and Onal scores were developed and internally and externally validated in different studies with similar AUC scores between 0.6 and 0.7. For PCNL practice, two nomograms were developed and internally validated (CMUN, SKS) but not externally validated. The Guy's stone score was found to have the lowest overall accuracy in predicting stone-free rates in the externally validated nomograms studies. Nine of the fourteen studies included were judged as having a high risk of bias in their overall judgement.

CONCLUSION

The systematic review findings should be interpreted with caution given the heterogeneity of included studies. There is no difference between the use of the Dogan or Onal score for predicting outcomes associated with ESWL. For predicting outcomes of PCNL, CROES had the greatest supportive evidence, whilst the SKS or CMUN scores lack external validation and require further evaluation to assess their utility in predicting PCNL outcomes.

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.

Nomograms predicting the outcomes of endoscopic treatments for pediatric upper urinary tract calculi

OBJECTIVES

To demonstrate the efficacy and safety of mini-percutaneous nephrolithotomy, micro-percutaneous nephrolithotomy, and flexible ureteroscopy for pediatric upper urinary tract calculi and to develop nomograms predicting surgical outcomes.

METHODS

A prospectively managed database containing children who were diagnosed with upper urinary tract calculi and treated with mini-percutaneous nephrolithotomy, micro-percutaneous nephrolithotomy, and flexible ureteroscopy between June 2014 and April 2019 was analysed. Patient demographics, intraoperative data, stone characteristics, stone-free rate, and complication rate were analysed and compared. Nomograms predicting the postoperative stone-free rate and complication rate were established based on predictors, and internal validation was performed. Calibration curves and decision curves were generated to assess the predictive efficacy and clinical benefit.

RESULTS

Forty-three children underwent mini-percutaneous nephrolithotomy on 56 sides in 47 operations, 30 children underwent micro-percutaneous nephrolithotomy on 30 sides in 30 operations, and 275 children underwent flexible ureteroscopy on 320 sides in 288 operations. The stone-free rates were 88.5% (282/320) for flexible ureteroscopy, 89.3% (50/56) for mini-percutaneous nephrolithotomy, and 90.0% (27/30) for micro-percutaneous nephrolithotomy (P = 0.94). And the complication rates were 19.8% (57/288), 36.2% (17/47), and 33.3% (10/30), respectively (P = 0.02). Nomograms based on stone characteristics, operation duration, and the physical condition of the child were shown to have good discrimination and calibration. The area under the curve of the models was 81% for stone-free rate and 73% for complication rate. The calibration curves showed that the nomogram might underestimate the probability of stone-free rate when the threshold was below 82% and might overestimate the risk of complication rate when the threshold was over 25%. The decision curves demonstrated that the Capital Medical University nomograms improved clinical risk prediction against threshold probabilities of stone-free rate ≤20% and complication rate ≤10%.

CONCLUSIONS

Both the percutaneous nephrolithotomy and flexible ureteroscopy procedures could have acceptable stone-free rates when treating pediatric stones. The Capital Medical University nomograms performed well in helping to predict stone-free and complication rates.

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.

Critical Application of Adult Nephrolithometric Scoring Systems to Children Undergoing Mini-Percutaneous Nephrolithotomy

Objective: To evaluate and compare the ability of the Guy's stone score (GSS), the S.T.O.N.E. nephrolithometry, and the Clinical Research Office of the Endourology Society (CROES) nomogram to predict the outcome of mini-percutaneous nephrolithotomy (MPNL) in children, and to identify which of the predictors involved in these scoring systems can separately affect this outcome. Patients and Methods: All children younger than 14 years who had MPNL in our center over a period of 3 years were included prospectively. Bivariate analyses were done to evaluate the associations of the three scoring systems and the predictors composing them with single-session stone clearance and complications. Receiver operating characteristic (ROC) curve analyses of the three scoring systems were conducted to evaluate and compare their abilities to predict the outcomes. Decision curve analyses for the three scoring systems were conducted to evaluate the clinical benefit of using each of them to predict stone clearance. Results: We consecutively enrolled 92 renal units in 89 children with a median age of 9.5 years. Single-session stone clearance was achieved in 76 (82.6%) renal units. Complications occurred with 19 (20.7%) procedures. Stone multiplicity (p = 0.043), staghorn stone (p = 0.007), prior stone treatment (p < 0.001), number of calices involved (p = 0.006), stone burden (p = 0.003), GSS (p < 0.001), S.T.O.N.E. nephrolithometry (p = 0.012), and CROES nomogram (p < 0.001) had significant associations with stone clearance. Only stone attenuation was significantly associated with complications (p = 0.031). For prediction of stone clearance, CROES nomogram demonstrated the greatest area under the ROC curve and the greatest net benefit on decision curve analyses. Conclusions: For children undergoing MPNL, CROES nomogram is the best to predict stone clearance. However, none of the studied scoring systems predicted complications efficiently.

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.

Comparison of Guy's Stone Score and clinical research of the endourological society nomogram for predicting surgical outcomes after pediatric percutaneous nephrolithotomy: a single center study

BACKGROUND

The aim of this study was to compare the efficacy of Guy's Stone Score (GSS) and Clinical Research of the Endourological Society (CROES) Nomogram in predicting PCNL outcomes in the pediatric patients with kidney stone.

METHODS

A retrospective review of the clinical data of 120 pediatric patients who underwent PCNL between August 2004 and February 2016 was performed. Patients were grouped according to stone-free (SF) status and complication status. The patients whose history, preoperative physical examination records, biochemical analysis, imaging records were available and who did not neglect the follow-up, were included in the study. The stone size measurement and the scoring system calculation were always performed by the same surgeon. Multivariate logistic regression analysis were performed to identify the factors associated with SF status and complication status.

RESULTS

CROES score was significantly higher in SF patients compared to the patients with residual stones (P=0.009), while stone burden and GSS were significantly lower (P=0.023 and P=0.025). Median hospitalization day of patients with complications was significantly higher compared to the patients without complication (P=0.005). To have stones located in multiple calyces was the only statistically significant condition when two groups were compared (P=0.014). In multivariate analysis, CROES score was the independent factor associated with SF status (OR:0.984 95% CI: 0.959-1.010 P=0.017) and to have stones located in multiple calyces was the independent factor associated with complication status (OR:0.265 95% CI:0.087-0.808 P=0.02).

CONCLUSIONS

CROES nomogram is associated with the SFR while GSS is not. Both scoring systems do not have predictive accuracy on complication status. Further studies are required to make modifications in the scoring systems in the pediatric population.

A new simple scoring system for prediction of success and complication rates in pediatric percutaneous nephrolithotomy: stone-kidney size score

INTRODUCTION

Nomograms and scoring systems designed for predicting the success of percutaneous nephrolithotomy (PCNL) in adults are currently available. However, no scoring system currently exists primarily for predicting PCNL success in children.

OBJECTIVES

The objective of this study was to develop a scoring system to predict the stone-free and complication rates by using pre-operative parameters.

STUDY DESIGN

A retrospective analysis was conducted on data from 434 renal units belonging to patients with kidney stones who underwent PCNL between 1997 and 2017. Renal stone index was calculated by dividing the length of the stone along its longest axis by the length of the kidney along its longest axis. Guy's Stone scores, S.T.O.N.E scores, and CROES scores for adults were calculated by filling in the variables for each patient. Factors that predicted success and complications were examined by univariate and multivariate analyses.

RESULTS

Mean age was 8.3 (1-16) years, and male to female ratio was 236:165. When stone-free patients were compared with other patients, there was a statistically significant difference in the average stone/kidney index (SKI) value (stone size/kidney size on longitudinal axis) (0.266 vs 0.339, P < 0.001). In multivariate analysis, factors that predicted success were the SKI and number of stones. A newly developed scoring scale, the stone-kidney score (SKS), combined scores for both the SKI and the number of stones into one value. A minimum total SKS score was 2, and a maximum total SKS score was 4. Success rates for SKS scores of 2, 3, and 4 were 86.4%, 73%, and 62.9% (P < 0.001), respectively. Complication rates for SKS scores of 2, 3, and 4 were 13%, 22.1%, and 23.8%, respectively.

DISCUSSION

The new scoring system has only two variables (number of stones and SKI) and three risk groups. An SKS score is easier to use and calculate. An SKI value can be simply calculated on any imaging modality by dividing the length of the stone along its longest axis by the length of the kidney along its longest axis. As in the new scoring system, the SKI value combined with the number of stones is useful in predicting stone-free rates after PCNL.

CONCLUSION

When evaluated together, the SKI and presence of multiple stones may predict stone-free rates pre-operatively. The SKS is an individual-specific method that can be easily used in pediatric clinical practice. Further studies are required to develop and standardize this method.

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.