Seoul National University Renal Stone Complexity Research Articles

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

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). 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 4mm 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. 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). 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.

Endoscopic combined intrarenal surgery versus percutaneuos nephrolithotomy for complex pediatric stone disease: A comparative analysis of efficacy and safety

INTRODUCTIONDecision-making for complex pediatric urinary system stone disease is still a challenge for pediatric urologists. The interest in supine percutaneous nephrolithotomy (PCNL) is increasing among centers to achieve high surgical success rates with less morbidity. Despite advanced retrograde intrarenal surgery armamentarium, percutaneous approaches remain the first-line surgical treatment modality for >2 cm and complex renal stones. There are no comparative studies yet in the literature for pediatric endoscopic combined intrarenal surgery (ECIRS) OBJECTIVEIn this study, we aimed to contribute to the literature by evaluating the safety and efficacy of ECIRS by comparing it with PCNL. STUDY DESIGNPatients under 18 years of age who underwent PCNL and ECIRS for urinary tract stone disease at our Pediatric Urology department between 2012 and 2024 were included. Preoperative (demographic characteristics, stone characteristics, biochemical parameters), perioperative (duration of surgery, number of accesses, lasing and fluoroscopy times, endoscopic and fluoroscopic stone-free rates) and postoperative (hospital stay, urinary tract infection, complication and radiological stone-free rates) parameters were retrospectively evaluated. RESULTSA total of 68 children [28 (41%) girls and 40 (59%) boys] aged 5 (0-17) years were included in the study. ECIRS was performed in 19 (28%), supine in 28 (41%) and prone PCNL in 21 (30%) patients. Age (p = 0.029), Guy's stone score (p<0.001), S.T.O.N.E. (p<0.001), and Seoul National University Renal Stone Complexity (S-ReSC) scores (p=0.001) for preoperative parameters were found to be higher in ECIRS group over both PCNL methods (Summary Table). However, Clinical Research Office of the Endourological Society (CROES) score was seen lower for ECIRS group patients compared to other groups (p=0.028).Surgery time (in favor of supine over prone PCNL), fluoroscopy time (in favor of ECIRS and Supine PCNL over Prone PCNL), preferred laser type (prone PCNL group was mostly performed with holmium laser, whereas other groups were balanced between Holmium and Thulium Fiber Laser) and exit strategy (the preferred exit strategy was DJ Stent in most of the ECIRS patients, whereas nephrostomy tube was used in some of the PCNL group) showed significant difference among the groups as perioperative parameters (p=0.042, <0.001, <0.001, <0.001, respectively). Surgery time was lower for supine PCNL compared to prone PCNL. For postoperative parameters, stone-free rates, complication rates and urinary tract infections were similar between the 3 groups, while a difference was detected in terms of length of hospital stay in favor of ECIRS over both supine and prone PCNL (p = 0.006). DISCUSSIONThe current trial suggests that stone-free and complication rates of ECIRS and supine PCNL were similar in the pediatric complex stone patients. Although, the stones in the ECIRS group we found to be more complex. Also, ECIRS was superior to PCNL in terms of fluoroscopy exposure and hospital stay. CONCLUSIONWith the widespread use of new generation ureteral access sheaths and flexible ureterorenoscopes, ECIRS may have an important role in treatment of complex pediatric kidney stones.

A new protocol for renal collecting system sterilization with antibiotic irrigation during lithotripsy in retrograde intrarenal surgery: a prospective, comparative study

PurposeTo present a new protocol using antibiotic irrigation during lithotripsy in retrograde intrarenal surgery (RIRS) to provide sterility of the renal collecting system.MethodsThis prospective study included 102 patients who underwent RIRS between January 2022 and August 2023. The patients were examined in two groups as those who received antibiotic irrigation (n:51) and standard irrigation (n:51). In the antibiotic irrigation group, 80 mg of gentamicin was dissolved in normal saline in a 3 L irrigation pouch to obtain a 26.7 mg/L concentration. In the standard irrigation group, normal saline was used. Preoperative information, including age, sex, body mass index (BMI), ASA score, stone side, volume, and density, and the Seoul National University Renal Stone Complexity (S-ReSC) score. The groups were compared with respect to postoperative fever (> 38 °C), urinary tract infection (UTI), systemic inflammatory response syndrome (SIRS), infectious complications such as sepsis, and stone-free rate.ResultsNo statistically significant difference was determined between the groups with respect to age, sex, BMI, ASA score, stone side, volume and density, and S-ReSC score (p > 0.05 for all). Statistically significant differences were determined between the groups with respect to postoperative fever (p = 0.05), SIRS (p = 0.05), and hospital length of stay (p = 0.05). Sepsis was observed in one patient in the standard irrigation group and in none of the antibiotic irrigation group.ConclusionThe reliability, efficacy, and utility of antibiotic irrigation during lithotripsy in RIRS were presented in this study as a new protocol for sterilization of the renal collecting system which will be able to reduce infectious complications.

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.

The Consecutive 200 Cases of Endoscopic-Combined Intrarenal Surgery: Comparison between Standard and Miniature Surgeries.

Background and Objectives: Percutaneous nephrolithotomy (PCNL) is still the gold-standard treatment for large and/or complex renal stones. Endoscopic combined intrarenal surgery (ECIRS) was developed with the goal of minimizing the number of access tracts of PCNL while simultaneously improving the one-step stone-free rate (SFR). The aim of this study was to share the experience of the consecutive 200 cases of ECIRS in one institute and analyze surgical outcomes of mini-ECIRS and standard ECIRS. Materials and Methods: We performed ECIRS for 200 adult patients between July 2017 and January 2020. An ECIRS was performed with the patient under general anesthesia in the intermediate-supine position. Surgeries were finished using a tubeless technique with a simple ureteral stent insertion. Results: There were significant differences in the mean maximal stone length (MSL), the variation coefficient of stone density (VCSD), the linear calculus density (LCD), the Seoul National University Renal Stone Complexity (S-ReSC), and the modified S-ReSC scores in stone characteristics, and estimated blood loss (EBL) and operation time in peri-operative outcomes between conventional and mini-ECIRS. After propensity-score matching, there was only a difference in EBL between the two groups. In logistic regression models, MSL [odds ratio (OR) 0.953; 95% confidence interval (CI) 0.926-0.979; p < 0.001], LCD (OR 4.702; 95% CI 1.613-18.655; p = 0.013) were significant factors for the success rate after ECIRS. Conclusions: In patients who underwent a mini-ECIRS, the stones were relatively smaller and less complex, and the operation time was shorter. However, if the size of stones was similar, there was no difference in the success rate, but EBL was lower in mini-ECIRS than in standard surgery.

External Validation of the Seoul National University Renal Stone Complexity Scoring System

Background: Preoperative determination of patient characteristics and the complexity of renal calculi is essential for optimizing the outcomes of percutaneous nephrolithotomy (PCNL). The Seoul National University Renal Stone Complexity (S-ReSC) scoring system is a popular system for predicting stone-free rates (SFR). Objective: To assess the predictive accuracy of the S-ReSC scoring system for PCNL in an external cohort. Materials and Methods: The perioperative data of consecutive patients undergoing PCNL in the standard prone position from January 2011 until August 2020 and S-ReSC scores assigned preoperatively were retrospectively analysed. Results: The study included 270 patients undergoing PCNL. The mean S-ReSC score was 5.4&plusmn;2.9. The overall SFR was 60.7%. The SFRs in the low- (1 to 2), intermediate- (3 to 4), and high-score (5 to 9) groups were 100%, 97.8%, and 27.3%, respectively. Multivariate logistic regression showed that the S-ReSC score, stone size, number of stones, and operative time were independent predictors of the stone-free status after PCNL (p&lt;0.001, p=0.015, p=0.004, and p=0.015, respectively). The area under the curve of the S-ReSC score was 0.949, indicating high predictive accuracy. Moreover, the S-ReSC score significantly correlated with estimated blood loss (r=0.15; p=0.014), and operative time (r=0.14; p=0.025). Conclusion: The S-ReSC score is highly useful for nephrolithiasis assessments and is a reliable predictor of the SFR, bleeding and operative time. Keywords: Renal calculus; S-ReSC; Percutaneous nephrolithotomy; Stone-free rate

External Validation and Comparison of Nephrolithometric Scoring Systems Predicting Outcomes of Retrograde Intrarenal Surgery.

Introduction: Preoperative assessment of renal stones is essential to selecting treatment options and achieving high success rates; thus, some nephrolithometric scoring systems have been developed by using preoperative clinical data and stone characteristics. Initially, nomograms predicting stone-free rates (SFRs) were designed for percutaneous nephrolithotomy. After this, some were modified, and new scoring systems were developed for retrograde intrarenal surgery (RIRS). In this study, we aimed at validating and comparing the accuracy of four scoring systems predicting the SFR of RIRS. Materials and Methods: We conducted a prospective study. The data of 110 consecutive patients who required RIRS for renal stones between May 2018 and February 2020 were evaluated. The patients were divided into four groups regarding total score: 0, 1, 2, ≥3 according to the Resorlu-Unsal Stone Score (RUSS). The scores were calculated between 5 and 15 for the size of the stone, topography or location, degree of obstruction of the urinary system, number of stones, and evaluation of Hounsfield units (S.T.O.N.E.) scoring system. Modified Seoul National University Renal Stone Complexity (S-ReSC) scores of the patients were between 1 and 12. Finally, the patients were classified between 4 and 10 points with the R.I.R.S. scoring system. Results: The mean RUSS, S.T.O.N.E., R.I.R.S., and modified S-ReSC scores were 1.14 (±0.818), 10.78 (±1.499), 6.50 (±1.305), and 2.29 (±1.710), respectively. The area under curve values of RUSS, S.T.O.N.E., R.I.R.S., and S-ReSC were 0.735 (95% confidence interval [CI] 0.623-0.826), 0.725 (95% CI 0.626-0.823), 0.752 (95% CI 0.646-0.857), and 0.755 (95% CI 0.660-0.849), respectively. Logistic regression analysis revealed that the RUSS was an independent predictive factor for SFR (p = 0.028). Conclusion: The results showed that all four scoring systems predict the SFRs for RIRS accurately. However, surgeons should prefer RUSS when all four nomograms are available, except when assessing single renal stones. In that case, S-ReSC should be used for assessment. Three other nomograms except the S.T.O.N.E. scoring system can be suitable for the assessment of lower caliceal stones.

A Comprehensive Comparison of Guy’s Stone Score, CROES Nomogram, S.T.O.N.E. Nephrolithometry, and the Seoul Renal Stone Complexity Scoring System in Predicting Perioperative Outcomes after Percutaneous Nephrolithotomy

Background: Various nephrolithometry scoring systems (NSS) are proposed to determine the structural configuration of kidney stones. Nevertheless, evidence of the comparison among these scoring systems in anticipating postoperative outcomes after percutaneous nephrolithotomy (PCNL) are limited. Objective: To compare the correlation of four NSS with stone-free rates and perioperative results following PCNL. Materials and Methods: The authors examined a retrospective study of patients with kidney stones who received PCNL. One hundred seventy-two patients admitted for surgery at Ramathibodi Hospital were assessed. Four NSS were compared, Guy’s Stone Score (GSS), the Clinical Research Office of the Endourological Society nephrolithometric nomogram (CROES), S.T.O.N.E. Nephrolithometry (STONE), and the Seoul National University Renal Stone Complexity (S-ReSC) scoring system. The authors evaluated the correlations between these four scoring systems with stone-free rates and postoperative outcomes. Results: The stone-free status was 53.5%. There were significant differences in the mean scores of the four systems between the stone-free group and the not stone-free group (1.97 versus 3.70, p&lt;0.05 in GSS; 242.40 versus 159.28, p&lt;0.05 in CROES; 6.64 versus 9.08, p&lt;0.05 in STONE; and 3.44 versus 8.41, p&lt;0.05 in S-ReSC). Multivariate analysis revealed only S-ReSC as independent preoperative factors for PCNL success (p&lt;0.001). Moreover, each scale had a significant correlation with blood loss, length of hospital stay, and operative time. Three scoring systems, all except STONE, were significantly associated with percentage change in estimated glomerular filtration rates (eGFR). There was no significant association among all four scoring systems with postoperative complications. Conclusion: All four NSS represent excellent predictors for stone-free rates and correlate well with surgical outcomes. Keywords: GSS, CROES, STONE, S-ReSC, Percutaneous nephrolithotomy

Evaluation of Nephrolithometric Scoring Systems to Predict Outcomes of Retrograde Intrarenal Surgery.

The aim of the study was to evaluate the predictive value of nephrolithometric scoring systems used to predict the complexity of renal stones for the outcomes of retrograde intrarenal surgery (RIRS). A total of 81 patients who underwent RIRS for nephrolithiasis between January 2013 and October 2017 were reviewed in this retrospective study. Guy's Stone Score (GSS), the S.T.O.N.E., Clinical Research Office of the Endourologic Society (CROES), and Seoul National University Renal Stone Complexity (S-ReSC) nephrolithometry scores were assessed by same researcher for each patient from preoperative non-contrast enhanced computed tomography scans. These nephrolithometric scores, stone characteristics and complications were compared in patients with/without residual stone. The median (IQR) age of patients (37 female/44 male) was 45 (20) years. The median (IQR) stone burden was 139.4 (125.4) mm2 and the mean Hounsfield unit (HU) value was 1034.46 ± 239.56. The stone burden, S.T.O.N.E. and S-ReSC scores were statistically significantly higher and the CROES score was significantly lower in patients with a residual stone (p < 0.001, for all). The incidence of residual stones was statistically significantly higher in patients with Grade 3 GSS (p = 0.018). While S.T.O.N.E., S-ReSC and CROES were significantly correlated with stone-free rates, GSS failed to correlate with stone-free status. According to the receiver operating characteristic (ROC) curve analysis, the predictive value of stone burden was higher for residual stones, compared to S-ReSC scoring (p < 0.05). Nephrolithometric scoring systems nomograms used to predict the PCNL success were not superior to stone burden in predicting the RIRS success.

Percutaneous Nephrolithotomy Outcomes Based on S.T.O.N.E., GUY, CROES, and S-ReSC Scoring Systems: The First Prospective Study.

Objective: To evaluate predictive capability and clinical applicability of the current nephrolithometric scoring systems of S.T.O.N.E. score, Guy's scoring system (GSS), CROES (Clinical Research Office of the Endourological Society) nomogram, and S-ReSC (Seoul National University Renal Stone Complexity) score for percutaneous nephrolithotomy (PCNL) outcomes in the same cohort in a prospective study. Methods: Consecutive patients undergoing PCNL between 2015 and 2018 were included calculating the four scores in the same cohort. Stone-free status (SFS), complications, operative time (OT), estimated blood loss (EBL), fluoroscopy time, and length of hospital stay were investigated. Receiver operator characteristic (ROC) curves for predictive accuracy and regression analysis for predictors of SFS were performed. Results: In all, 162 PCNLs were accomplished and analyzed. Overall, SFS was 75.9% and complication rate was 30.9%. The mean acquisition time of scores was 52.9 ± 0.5 seconds for GSS, 05.1 ± 0.3 seconds for S.T.O.N.E. score, 224 ± 3.1 seconds for CROES, and 102.6 ± 3.5 seconds for S-ReSC score. SFS had the best association with CROES grade. Clavien grade was associated with S.T.O.N.E. score. Moreover, EBL and OT had best association with S-ReSC score. All scores had comparable predictive accuracy on ROC curves regarding SFS. Stone essence and tract length are not different in cases with residual stones. Number of involved calyces, single vs multiple stones and renal pelvic obstruction were significant predictors of SFS in regression analysis. Conclusion: The four scoring systems had comparable predictive accuracy for SFS. However, S.T.O.N.E. and S-ReSC scores were easily applicable and provided better association with EBL and OT compared with the GSS score. Number of involved calyces, stone multiplicity, and renal pelvic obstruction were significant predictors of SFS; hence, further studies are needed to invent a universally agreeable scoring system covering reported shortcomings in the currently used scores.

External validation and comparison of the scoring systems (S.T.O.N.E, GUY, CROES, S-ReSC) for predicting percutaneous nephrolithotomy outcomes for staghorn stones: A single center experience with 160 cases

The aim of this study was validation and comparison of stone scoring systems (S.T.O.N.E, GUY, CROES, S-ReSC) used to predict postoperative stone-free status and complications after percutaneous nephrolithotomy (PCNL) for staghorn stones. A total of 160 patients who had staghorn renal stones and underwent PCNL between January 2012 and August 2015 were included in the current retrospective study. Guy, S.T.O.N.E., S-ReSC (Seoul National University Renal Stone Complexity) and CROES (Clinical Research Office of the Endourological Society) nephrolithometry scores were calculated for each patient, and their potential association with stone-free status, operative and fluoroscopy time, and length of hospital stay (LOS) were evaluated. Postoperative complications were graded according to the modified Clavien classification, and the correlation of scoring systems with postoperative complications was also investigated. The mean CROES, S.T.O.N.E, Guy and S-ReSC scores were 143.5 ± 33.6, 9.7 ± 1.6, 3.5 ± 0.5 and 6.2 ± 2.0 respectively. The overall stone-free rate was 59%. All scoring systems were significantly correlated with stone-free status in univariate analysis. However, Guy and S-ReSC scores were the only significant independent predictor in multivariate analysis. And all four nomograms failed to predict complication rates. Current study demonstrated that Guy and S-ReSC scoring systems could effectively predict postoperative stone-free status for staghorn stones. However all four scoring systems failed to predict complication rates.

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

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). 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. 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]). 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.

Modified Seoul National University Renal Stone Complexity score for retrograde intrarenal surgery

The Seoul National University Renal Stone Complexity (S-ReSC) score is a well-validated tool for the prediction of stone-free rate (SFR) after percutaneous nephrolithotomy. We modified the S-ReSC score system for application to retrograde intrarenal surgery (RIRS) and evaluated this score. A total of 88 patients who underwent RIRS from 2011 to 2013 were included. The modified S-ReSC score was assigned according to the number of sites involved in the renal pelvis (#1), superior and inferior major calyceal groups (#2-3), and anterior and posterior minor calyceal groups of the superior (#4-5), middle (#6-7), and inferior calyx (#8-9). If the stone was in the inferior sites (#3, #8-9), one additional point per site was added to the original score. The SFR was examined according to the modified S-ReSC score. To evaluate the predictive accuracy, the area under the receiver operating characteristic curve (AUC) was used and compared with the Resorlu-Unsal Stone (RUS) score. The SFR was 85.2% and was significantly decreased in the order of low (1-2: 94.2%), medium (2-4: 84.0%), and high (>4: 45.5%) modified ReSC score groups (p < 0.001). AUCs of the modified S-ReSC score (0.806) and score group (0.766) were higher than the AUC of the RUS score (0.692; p = 0.012 and p = 0.040, respectively). The modified S-ReSC score predicts the SFR after RIRS well. Furthermore, its predictive accuracy is higher than that of the RUS score.

External Validation and Evaluation of Reliability and Validity of the S-ReSC Scoring System to Predict Stone-Free Status after Percutaneous Nephrolithotomy

ObjectivesThe Seoul National University Renal Stone Complexity (S-ReSC) scoring system was developed to predict the stone-free rate (SFR) after single-tract percutaneous nephrolithotomy (PCNL). This study is an external validation of this scoring system.Materials and methodsA retrospective review included 327 patients who underwent PCNL at 2 tertiary referral centers. The S-ReSC score was assigned from 1 to 9 based on the number of sites involved. The stone free status was defined as either complete clearance or clinically insignificant residual fragments <4 mm in size at 1 month follow-up imaging. Inter-observer and test-retest reliabilities were evaluated. The statistical performance of the prediction model was assessed by its predictive accuracy, predictive probability, and clinical usefulness.ResultsThe overall SFR was 65.4%. SFRs were 83.9%, 47.6%, and 21.4% in low (1–2), intermediate (3–4), and high (5–9) score groups, respectively, with significant differences (P<0.001). Inter-observer and test-retest reliabilities revealed almost perfect agreements. External validation of the S-ReSC scoring system revealed an AUC of 0.731 (95% CI 0.675–0.788). The AUC of 3-titered S-ReSC score groups was 0.691 (95% CI, 0.629–0.753). The calibration plot showed that the predicted probability of SFR had a concordance comparable to that of the observed frequency. The Hosmer–Lemeshow goodness-of-fit statistic revealed an adequate performance of the predictive model (P = 0.10). Inter-observer and test-retest reliability showed a good level of agreement.ConclusionsThe S-ReSC scoring system is useful in predicting the post-PCNL SFR and in describing the complexity of renal stones.

Seoul National University Renal Stone Complexity Score for Predicting Stone-Free Rate after Percutaneous Nephrolithotomy

ObjectivesCurrently, no standardized method is available to predict success rate after percutaneous nephrolithotomy. We devised and validated the Seoul National University Renal Stone Complexity (S-ReSC) scoring system for predicting the stone-free rate after single-tract percutaneous nephrolithotomy (sPCNL).Patients and MethodsThe data of 155 consecutive patients who underwent sPCNL were retrospectively analyzed. Preoperative computed tomography images were reviewed. The S-ReSC score was assigned from 1 to 9 based on the number of sites involved in the renal pelvis (#1), superior and inferior major calyceal groups (#2–3), and anterior and posterior minor calyceal groups of the superior (#4–5), middle (#6–7), and inferior calyx (#8–9). The inter- and intra-observer agreements were accessed using the weighted kappa (κ). The stone-free rate and complication rate were evaluated according to the S-ReSC score. The predictive accuracy of the S-ReSC score was assessed using the area under the receiver operating characteristic curve (AUC).ResultsThe overall SFR was 72.3%. The mean S-ReSC score was 3.15±2.1. The weighted kappas for the inter- and intra-observer agreements were 0.832 and 0.982, respectively. The SFRs in low (1 and 2), medium (3 and 4), and high (5 or higher) S-ReSC scores were 96.0%, 69.0%, and 28.9%, respectively (p<0.001). The predictive accuracy was very high (AUC 0.860). After adjusting for other variables, the S-ReSC score was still a significant predictor of the SFR by multiple logistic regression. The complication rates were increased to low (18.7%), medium (28.6%), and high (34.2%) (p = 0.166).ConclusionsThe S-ReSC scoring system is easy to use and reproducible. This score accurately predicts the stone-free rate after sPCNL. Furthermore, this score represents the complexity of surgery.