Utility of the Guy's Stone Score Based on Computed Tomographic Scan Findings for Predicting Percutaneous Nephrolithotomy Outcomes

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.

Clinical Utility of S.T.O.N.E, Guy's Scoring System, and Renal Stone Complexity Scoring in Predicting Outcome of Single-Tract Percutaneous Nephrolithotomy

BACKGROUND

Several imaging-based scores have been developed to predict postoperative stone-free state (SFS) and complications. This study aimed to assess the accuracy of the S.T.O.N.E., Guy Scoring System (GSS), and Seoul National University Renal Stone Complexity (S-ReSCS) scores in predicting the outcomes of single-tract percutaneous nephrolithotomy (ST-PCNL). This scoring system holds paramount importance for low-income and low-middle-income countries (LMICs), as it is inexpensive and cost-effective for the healthcare system.

METHODOLOGY

This retrospective study was carried out with 147 participants. Based on the preoperative computerized tomographic (CT) scan, each patient's S.T.O.N.E. score, GSS, and S-ReSCS were recorded. The modified Clavien grading system was used to document intra- and postoperative complications.

RESULTS

The mean age of the sample population was 45 years. SFS was achieved in 110 (74.8%) patients. The number of calyces involved (p = 0.008), S.T.O.N.E. scoring (p = 0.001), GSS (p = 0.008), and S-ReSCS (0.001) correlated well with the SFS. Forty-nine (33.33%) patients developed complications. The most common complications fell within Clavien grade II. No statistical significance was noted between the S.T.O.N.E. score, GSS, and S-ReSCS with the modified Clavien grading system.

CONCLUSION

The S.T.O.N.E. scoring, GSS, and S-ReSCS have a high predictive value for achieving SFS in ST-PCNL. In addition, findings from LMICs are comparable with those from the rest of the world.

Is Guy's stone score useful for predicting outcomes in percutaneous nephrolithotomy?

INTRODUCTION

Percutaneous Nephrolithotomy (PCNL) is currently the treatment of choice in large kidney stones. Guy's stone score was developed to predict treatment outcomes. The aim of this study was to evaluate the relationship between Guy's score and outcomes in our institution.

MATERIALS AND METHODS

The medical records of patients diagnosed with urolithiasis and treated by PCNL were retrospectively evaluated between January 2017 and December 2018. Analyzed data included: age, sex, Guy's score based on preoperative findings, transfusion, stone-free rate and requirement of auxiliary procedures. Chi-square test was used for the comparison of proportions. Odds ratios (OR) with confidence intervals (CIs) of 95% were calculated by logistic regression.

RESULTS

A total of 386 patients, 53.89% female, mean age of 45.59 ± 15 years were analyzed. Guy's score was as follows: 112 patients (29.04%) were classified as Guy I, 92 patients (23.82%) as Guy II, 94 patients (24.34%) as Guy III, and 88 patients (22.80%) as Guy IV. There were no differences between groups in terms of blood transfusions. Stone-free rate was 96.43% (n = 108) for patients Guy I; 84.78% (n = 72) for Guy II; 76.59% (n = 72) for Guy III and 50% (n = 44) for Guy IV categories (p < 0.0001). Taking as a reference Guy I group, the OR to require new treatment for residual stones were: Guy II 4.85 (CI = 0.95 to 24.60, P = 0.05) to Guy III 8.25 (CI = 1.73 to 39.44, P = 0.008) and Guy IV 27 (CI = 5.84 to 124.70; p < 0.0001).

CONCLUSION

There was a statistically significant association between Guy's Score and stone-free rates following PCNL. Guy's score was useful to predict results of PCNL in our group.

Comparison of percutaneous nephrolithotomy and retrograde intrarenal surgery outcomes for kidney stones larger than 2 cm from Guy's stone scoring system perspective

OBJECTIVE

To compare surgical outcomes of percutaneous nephrolithotomy (PNL) and retrograde intrarenal surgeries (RIRS) as a result of kidney stones larger than 2 cm, together with Guy's stone scores (GSS).

MATERIALS AND METHODS

The data of 811 patients with stone sizes 2-6 cm were operated using PNL (n = 361) and RIRS (n = 450) reviewed retrospectively. GSS were graded 1, 2, 3 or 4 according to the computed tomography findings. Stone-free rate (SFR), operation times, length of hospital stay (LOHS) and Clavien complications (CC) were recorded.

RESULTS

Although mean operative times were significantly longer in the RIRS group than the PNL group in GSS grades 1, 2 and 3 (P < .001), it was similar between the two groups in GSS grade 4 (P = .186). SFRs in the PNL and RIRS group were 90.3% and 58.4% on post-operative 10th day (P < .001), and it raised up to 95.3% and 81.6% after secondary interventions (P < .001). Significantly higher SFRs observed in the PNL group in GSS grades 1, 2 and 3 categories. On postoperative 10th day, the SFRs were similar in both GSS grade 4 categories (P = .06). LOHS was longer in the PNL group (P < .001). Although LOHS was significantly longer only in GSS grade 3 (P = .043) and GSS grade 4 (P < .001) in the PNL group, it was similar in GSS grade 1 and 2 between groups. Clavien complications increased in line with GSS in the PNL group (P < .001), but the difference did not differ between GSS grade 3 and 4.

CONCLUSION

SF of PNL in a single session and short operation time seems to be significant especially in GSS grades 1, 2 and 3 category stones. Although the number of patients in the GSS 4 group is very small to claim this, RIRS might be considered as an alternative to PNL in a special group of patients such as GSS grade 4 because of its lower complication rates and shorter LOHS.

THE FUNCTIONAL STATE OF THE RENAL PARENCHYMA AFTER VARIOUS VIDEO ENDOSURGICAL METHODS OF TREATMENT OF PATIENTS WITH LARGE AND COMPLEX KIDNEY STONES

The work is based on the analysis of literature data devoted to the problem of preserving the functional state of the kidneys with various video endoscopic methods of surgical treatment of large and complex kidney stones. The purpose of the review is to highlight the likelihood of deterioration in the functional state of the kidneys in the postoperative period. A detailed analysis of postoperative outcomes in various minimally invasive methods of treatment of patients with large and complex kidney stones was carried out, with an overview of the possibility of using dynamic nephroscintigraphy as a method of objectively assessing the functional state of the kidneys.

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.

Role of Preoperative Renal Stone Complexity Assessment by Guy's Stone Score as a Predictor of Percutaneous Nephrolithotomy Outcomes

INTRODUCTION

Various nephrolithometric scoring systems have recently emerged to predict the outcomes of percutaneous nephrolithotomy (PCNL). However, there is no consensus upon an ideal tool. The current study aimed to assess the correlation between Guy's stone score (GSS) and PCNL outcomes.

METHOD

This was a hospital-based observational study of 2-year duration. All patients electively undergoing PCNL for renal stones during the study period were included. Based on the imaging findings, the stones were categorized as simple (GSS I &amp; II) and complex (GSS III &amp; IV). The association between GSS and duration of the procedure, the number of percutaneous tracts needed, stone-free rate (SFR), and the severity of complications based on modified Clavien classification and postoperative stay were assessed.

RESULTS

Total number of the patients studied were 100 (n = 100), and most of the patients were in the category of GSS II (51%). Post-extrapolation of χ2 to Pearson's test, GSS demonstrated a significant association with duration of surgery, the number of percutaneous tracts needed, the severity of complications, and SFR.

CONCLUSIONS

Preoperative assessment of stone complexity by using GSS effectively correlated with SFR as well as other PCNL outcomes. Hence, we recommend utilizing this predictive tool for standardized documentation, preoperative planning, and better patient counseling.

Tranexamic acid in patients with complex stones undergoing percutaneous nephrolithotomy: a randomised, double-blinded, placebo-controlled trial

OBJECTIVES

To assess the efficacy and safety of single-dose tranexamic acid on the blood transfusion rate and outcomes of patients with complex kidney stones undergoing percutaneous nephrolithotomy (PCNL).

PATIENTS AND METHODS

In a randomised, double-blinded, placebo-controlled trial, 192 patients with complex kidney stone (Guy's Stone Scores III-IV) were prospectively enrolled and randomised (1:1 ratio) to receive either one dose of tranexamic acid (1 g) or a placebo at the time of anaesthetic induction for PCNL. The primary outcome measure was the occurrence rate of perioperative blood transfusion. The secondary outcome measures included blood loss, operative time, stone-free rate (SFR), and complications. ClinicalTrials.gov identifier: NCT02966236.

RESULTS

The overall risk of receiving a blood transfusion was reduced in the tranexamic acid group (2.2% vs 10.4%; relative risk, 0.21, 95% confidence interval [CI] 0.03-0.76, P = 0.033; number-needed-to-treat: 12). Patients randomised to the tranexamic acid group had a higher immediate and 3-month SFR compared with those in the placebo group (29% vs 14.7%, odds ratio [OR] 2.37, 95% CI 1.15-4.87, P = 0.019, and 46.2% vs 28.1%, OR 2.20, 95% CI 1.20-4.02, P = 0.011, respectively). Faster haemoglobin recovery occurred in patients in the tranexamic acid group (mean, 21.3 days; P = 0.001). No statistical differences were found in operative time and complications between groups.

CONCLUSIONS

Tranexamic acid administration is safe and reduces the need for blood transfusion by five-times in patients with complex kidney stones undergoing PCNL. Moreover, tranexamic acid may contribute to better stone clearance rate and faster haemoglobin recovery without increasing complications. A single dose of tranexamic acid at the time of anaesthetic induction could be considered standard clinical practice for patients with complex kidney stones undergoing PCNL.

Percutaneous nephrolithotomy in patients with spinal cord injury: should all these patients be automatically assigned a Guy's stone score of 4?

PURPOSE

To assess the complication and stone-free rates of PCNL in patients with spinal cord injury (SCI) and to evaluate whether this population should be assigned a Guy's stone score (GSS) of 4.

METHODS

A case-control study was conducted, and electronic charts were reviewed to search for patients with SCI, bladder dysfunction, and kidney stones who had undergone PCNL. Control cases were randomly selected from among patients with complete staghorn calculus (GSS = 4).

RESULTS

One hundred and seventeen patients were included. Patients with SCI had a significant shorter operative time (119 vs. 141 min; p = 0.018). There were no significant differences between the groups in terms of the patients' position, number of renal tracts, bleeding or transfusion rate; however, there was a significantly higher complication rate (23.1% vs. 7.8%; p = 0.009) and a longer hospital stay (5.8 vs. 3.1 days; p = 0.002) among patients with SCI. With regards to the stone-free rate in patients with different grades of GSS patients with SCI who had a GSS of 1 had a stone-free rate of 85.7%, while those with a GSS of 2, 3, or 4 had 50%, 50%, and 31.5%, respectively (p = 0.024). Only patients with a GSS of 4 in the SCI group had outcomes that were similar to those of control patients (31.5% vs. 31.6%).

CONCLUSION

Patients with SCI should not be automatically assigned GSS 4. Stone-free rate is related to stone burden in these patients, although they do show a higher complication rate and a longer hospital stay than non-neurological patients.

Impact of Obesity on Outcomes of Supine Percutaneous Nephrolithotomy

Objectives: To determine whether obesity has an impact on the outcomes of supine percutaneous nephrolithotomy (PCNL). Patients and Methods: We retrospectively evaluated a prospectively created database of patients who underwent PCNL in the supine position from June 2009 to June 2014. The patients were divided into two groups according to their body mass index (BMI): <30 kg/m² (group 1, nonobese) and ≥30 kg/m² (group 2, obese). Pre, peri, and postoperative data were analyzed. Stone complexity was classified according to Guy's stone score. The primary endpoint was the absence of stone fragments of ≥4 mm on CT scans at postoperative day 1. Complications were graded according to the modified Clavien classification. Results: Of the 401 patients, 307 (76.6%) were nonobese and 94 (23.4%) were obese. Regarding demographic and stone characteristics, group 2 (BMI ≥30 kg/m²) had a higher percentage of female patients (67.3% vs 50.4%, p = 0.002) and a higher mean BMI (34.8 vs 24.5 kg/m², p < 0.001) than group 1. Success rates were not statistically different between the groups (group 1 = 61.8%, group 2 = 51%, p = 0.08). There were no differences in the transfusion rate (group 1 = 2.9%, group 2 = 4.2%, p = NS) or total number of complications greater than Clavien grade 1 (group 1 = 13.6%, group 2 = 13.8%, p = NS). Conclusion: In a retrospective study of 400 patients undergoing PCNL, the outcomes were not different between nonobese and obese patients. To our knowledge, this is the first study evaluating these outcomes for PCNL performed in the supine position. Further multicenter and prospective studies are necessary to verify these findings.

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.

Comparing different kidney stone scoring systems for predicting percutaneous nephrolithotomy outcomes: A multicenter retrospective cohort study

OBJECTIVE

To compare the predictive performance of five previously described scoring systems (i.e., S.T.O.N.E., Guy's, Clinical Research Office of the Endourological Society (CROES), the Seoul National University Renal Stone Complexity (S-RESC) and the new Stone Kidney Size (SKS) score) for postoperative outcomes regarding stone-free rate (SFR) and complications in adult patients.

METHODS

Data from 349 patients who underwent percutaneous nephrolithotomy (PCNL) in three urology departments were analyzed. SKS, S.T.O.N.E., S-ReSC, CROES and Guy's nephrolithometry scoring systems were used to retrospectively calculate predictions for each patient. Univariate and multivariate analyses were performed to evaluate factors associated with SFR and complication rates. Receiver operating characteristic (ROC) curves were generated and areas under curves (AUC) were compared to identify the method with the highest predictive value.

RESULTS

Median SKS, S.T.O.N.E., S-ReSC, CROES and Guy's scores were 4, 7, 3, 170.8 and 2, respectively. Overall, SFR was 67.0% (234/349) with a complications rate of 36.7% (128/349). AUCs of each method for predicting stone-free status, highlighted reasonable predictive capabilities with 0.709, 0.806, 0 0.869, 0.207, and 0.735, respectively; however, the S-ReSC scoring system had the best discriminative performance. According to multivariate logistic regression and AUC results, none were effectively capable of predicting complications.

CONCLUSIONS

All scoring systems correlated significantly with stone-free status; although, S-ReSC appears to have the greatest predictive ability. This method is also relatively easy to implement and highly reproducible. However, none of the methods analyzed are able to accurately predict postoperative complications.

Percutaneous Nephrolithotomy in Horseshoe Kidneys: Results of a Multicentric Study

Objective: To report the outcomes of percutaneous nephrolithotomy (PCNL) in horseshoe kidneys (HSK) in 12 institutions worldwide and evaluate the impact of patient position during operation. Methods: We carried out a retrospective analysis of PCNL procedures performed between 2008 and 2018 in patients with HSK. Pre-, peri-, and postoperative data were collected, and a subgroup analysis was performed according to patient position. Success was defined as an absence of >4-mm fragments. Values of p < 0.05 were considered significant. Results: We analyzed 106 procedures. The transfusion, complication, and immediate success rates (ISRs) were 3.8%, 17.5%, and 54.7%, respectively. The final success rate (FSR) increased to 72.4% after a mean of 0.24 secondary procedures. Logistic regression showed that higher body mass index (BMI) and stone size were significantly associated with residual fragments ≥4 mm. Sixty-seven patients (63.2%) were treated in prone and 39 (36.8%) in supine position. The prone group had a significantly higher BMI than the supine group (30.1 vs 27.7, p = 0.024). The transfusion, complication, and ISRs between the prone and supine groups were 4.5% vs 2.6% (p = 0.99), 16.9% vs 18.4% (p = 0.99), and 52.5% vs 69.2% (p = 0.151), respectively. Surgical time was significantly longer in the prone group (126.5 vs 100 minutes, p = 0.04). Upper pole was the preferred access in 80.3% of the prone group and 43.6% of the supine group (p < 0.001). The prone group had significantly more Clavien 2 complications than the supine (p = 0.013). The FSR in the prone and supine groups increased to 66.1% and 82.1% after 0.26 and 0.21 secondary procedures, respectively. No complications higher than Clavien 3 occurred. Conclusion: PCNL in patients with HSK is safe and effective with a low complication rate. Higher BMI and stone size negatively impacted outcomes. Supine PCNL may be an option for treating kidney stones in patients with HSK.

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.

Preoperative imaging in staghorn calculi, planning and decision making in management of staghorn calculi

Objective

Staghorn calculi present a particular and challenging entity of stone morphology. Treatment is associated with lower stone-free rates and higher complication rates compared to non-staghorn stones. In this review we looked for the most relevant data on preoperative imaging and access planning to help decision making for percutaneous surgery with this complex condition.

Methods

We conducted a PubMed search of publications in the past 2 decades that include relevant information on the planning for management of staghorn stones. Non-contrast computerized tomography (NCCT) is indeed the standard imaging tool for percutaneous nephrolithotomy (PCNL); additional tools such as three-dimensional computed tomography (CT) reconstruction of the staghorn calculus may help plan access in complex cases. Ultrasound guided percutaneous access may be considered for staghorn stones when planning upper pole access in kidney malposition or complex intrarenal anatomy or with complex body habitus. Wideband doppler ultrasound and real-time virtual sonography can assist. New technologies to improve kidney access such as Uro Dyna-CT or electromagnetic sensor have been reported, but have not shown utilization in staghorn cases. Staghorn morphometry-based prediction algorithms may predict the number of tract(s) and stage(s) for PCNL monotherapy. Lower pole access can be equally effective as upper pole when planning for staghorn and complex stones, with significantly less complications rate; Stone-Tract length-Obstruction-Number of involved calyces-Essence of stone density (STONE) nephrolithometry seems to be the best system to predict outcomes of PCNL in staghorn cases. There is a growing trend of endoscopic combined intrarenal surgery (ECIRS) in concordance with PCNL to treat larger stones. Conservative management of staghorn calculi is an undesired option, but can be an alternative for a carefully selected group of high-risk patients.

Conclusion

Staghorn stones may lead to deterioration of renal function and life-threatening urosepsis. This entity should be managed aggressively with planning ahead for surgery using the different tools available as the cornerstone for a successful outcome.

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]

The evolution of percutaneous nephrolithotomy: Analysis of a single institution experience over 25 years

INTRODUCTION

Over time, the incidence of nephrolithiasis has risen significantly, and patient populations have become increasingly complex. Our study aimed to determine the impact of changes in patient demographics on percutaneous nephrolithotomy (PCNL) outcomes.

METHODS

A retrospective analysis of a prospectively collected database was carried out from 1990-2015. Patient demographics, comorbidities, stone and procedure characteristics were analyzed. Multivariate logistic regression was used to evaluate differences in operative duration, complications, stone-free rate, and length of stay.

RESULTS

A total of 2486 patients with a mean age of 54±15 years, body mass index (BMI) of 31±8, and stone surface area of 895±602 mm² were analyzed; 47% of patients had comorbidities, including hypertension (22%), diabetes mellitus (14%), and cardiac disease (13%). Complication rate was 19%, including a 2% rate of major complications (Clavien grade III-V). There was a statistically significant increase in patient age, BMI, and comorbidities over time, which was correlated with an increased complication rate (odds ratio [OR] 1.15; p=0.010). The overall transfusion rate was 1.0% and remained stable (p=0.131). With time, both OR duration (mean Δ 16 minutes; p<0.001) and hospital length of stay (mean Δ 2.4 days; p<0.001) decreased significantly. Stone-free rate of 1873 patients with available three-month followup was 87% and decreased significantly over time (OR 1.09; p<0.001), but was correlated with an increased use of computed tomography (CT) scans for followup imaging.

CONCLUSIONS

Despite an increasingly complex patient population, PCNL remains a safe and effective procedure with a high stone-free rate and low risk of complications.

Comparative study of percutaneous nephrolithotomy performed in the traditional prone position and in three different supine positions

Purpose:

To compare the outcomes of percutaneous nephrolithotomy (PCNL) performed in the prone position (PRON) and in three variations of the supine position.

Materials and Methods:

We performed a retrospective analysis of patients that underwent PCNL at our institution from June 2011 to October 2016 in PRON and in three variations of the supine position: complete supine (COMPSUP), original Valdivia (VALD), and Galdakao - modified Valdivia (GALD). All patients had a complete pre - operative evaluation, including computed tomography (CT). Success was defined as the absence of residual fragments larger than 4 mm on the first post - operative day CT.

Results:

We analyzed 393 PCNLs: 100 in COMPSUP, 94 in VALD, 100 in GALD, and 99 in PRON. The overall success rate was 50.9% and was similar among groups (p = 0.428). There were no differences between groups in the number of punctures, stone - free rate, frequency of blood transfusions, drop in hemoglobin level, length of hospital stay, and severe complications (Clavien ≥ 3). COMPSUP had a significantly lower operative time than the other positions. COMPSUP had lower fluoroscopy time than VALD.

Conclusion:

Patient positioning in PCNL does not seem to impact the rates of success or severe complications. However, COMPSUP is associated with a shorter surgical time than the other positions.

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.

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.

Impact of patient position on the outcomes of percutaneous neprolithotomy for complex kidney stones

Purpose:

To evaluate the impact of the patient position on the outcomes of PCNL among patients with complex renal stones.

Material and Methods:

From July 2011 to July 2014, we collected prospective data of consecutive patients who underwent PCNL. We included all patients with complex stones (Guy's Stone Score 3 or 4 (GSS) based on a CT scan) and divided them based on the position used during PCNL (prone or supine). The variables analyzed were gender, age, body mass index, ASA score, stone diameter, GSS, number of punctures, calyx puncture site, intercostal access and patient positioning. Complications were graded according to the modified-Clavien Classification. Success was considered if fragments ≤ 4mm were observed on the first postoperative day CT scan.

Results:

We analyzed 240 (46.4%) of 517 PCNL performed during the study period that were classified as GGS 3-4. Regarding patient positions, 21.2% were prone and 79.8% were supine. Both groups were comparable, although intercostal access was more common in prone cases (25.5% vs 10.5%; p=0.01). The success rates, complications, blood transfusions and surgical times were similar for both groups; however, there were significantly more visceral injuries (10.3% vs 2.6%; p=0.046) and sepsis (7.8% vs 2.1%; p=0.042) in prone cases.

Conclusion:

Supine or prone position were equally suitable for PCNL with complex stones and did not impact the success rates. However, supine position was associated with fewer sepsis cases and visceral injuries.

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.

Do 3D-calculated volume distribution of a stone in pelvicalyceal system affect complications of percutaneous nephrolithotomy?

In our study, we examined the effect of the three-dimensional (3D) stone segmentation volume and its ratio to the renal collecting system on complication rates. Data from141 patients who underwent PCNL surgery were analyzed retrospectively. Volume segmentation of both the renal collecting system and stones was obtained from 3D segmentation software with the images on CT data. After creation of a 3D surface volume rendering of renal stones and the collecting system, segmentation of the renal collecting system volume (RCSV) and analyzed stone volume (ASV) was analyzed and the ASV-to-RCSV ratio was calculated. Univariate analysis and multivariate logistic regression model were used to determine factors that affected complication status. Diagnostic value for the prediction of complication rates was analyzed using receiver operating characteristic (ROC) incline. Overall, there were 141 (92 male and 49 female) eligible patients included in the current study. The overall complication rate for PCNL monotherapy was 31.9%. Multivariate regression analysis (forward stepwise) revealed that the ASV-to-RCSV ratio and number of tracts were independent risk factors for developing complications (OR 1.17, p < 0.001; OR 7.87, p = 0.002; respectively). The ROC analysis revealed a cut-off value of 16.23% (AUC 0.869, p < 0.001, sensitivity 93.3%, specificity 78.1%) for the ASV-to-RCSV ratio. The distribution of stone burden volume in the pelvicalyceal system, which is calculated as a numerical value using the 3D volume segmentation method, is an important predictor of the complication rate before PCNL. The ASV-to-RCSV ratio as a quantitative value may be an instrument for urologists before surgery to help preoperative planning.

What is the quickest scoring system to predict percutaneous nephrolithotomy outcomes? A comparative study among S.T.O.N.E score, guy's stone score and croes nomogram

Objective:

To compare the application time and the capacity of the nomograms to predict the success of Guy's Stone Score (GSS), S.T.O.N.E. Nephrolithometry (STONE) and Clinical Research Office of the Endourological Society nephrolithometric nomogram (CROES) of percutaneous nephrolithotomy (PCNL), evaluating the most efficient one for clinical use.

Materials and Methods:

We studied 48 patients who underwent PCNL by the same surgeon between 2010 and 2011. We calculated GSS, STONE and CROES based on pre-operative non-contrast computed tomography (CT) images and clinical data. A single observer, blinded to the outcomes, reviewed all images and assigned scores. We compared the application time of each nomogram. We used an analysis of variance for repeated measures and multiple comparisons by the Tukey test. We compared the area under the ROC curve (AUC) of the three nomograms two by two to determine the most predictive scoring system.

Results:

The immediate success rate was 66.7% and complications occurred in 16.7% of cases. The average operative time was 122 minutes. Mean application time was significantly lower for the GSS (27.5 seconds) when compared to 300.6 seconds for STONE and 213.4 seconds for CROES (p<0.001). There was no significant difference among the GSS (AUC=0.653), STONE (AUC=0.563) and CROES (AUC=0.641) in the ability to predict immediate success of PCNL.

Conclusions:

All three nomograms showed similar ability to predict success of PCNL, however the GSS was the quickest to be applied, what is an important issue for routine clinical use when counseling patients who are candidates to PCNL.

Outcomes of more than 1 000 percutaneous nephrolithotomies and validation of Guy's stone score

OBJECTIVE

To present the experience with percutaneous nephrolithotomy (PCNL) at a high-volume Brazilian centre and to evaluate Guy's stone score (GSS) as a predictor of success and complications in PCNL.

PATIENTS AND METHODS

We prospectively evaluated patients who underwent PCNL between June 2011 and October 2016. Indications for PCNL included renal stones >2 cm in size and stones <2 cm in size in which first-line techniques had failed. All patients underwent a complete preoperative evaluation, including non-contrast-enhanced abdominal computed tomography (CT). Stone complexity was assessed using GSS. Success was defined as the absence of fragments >2 mm on CT on postoperative day 1. Complications were classified according to the Clavien grade.

RESULTS

A total of 1 066 PCNLs were performed on 891 patients. In all, 20.2% were classified as GSS1, 27.4% as GSS2, 35.0% as GSS3, and 17.4% as GSS4. The mean operating time was 108.44 min, and the mean fluoroscopy time was 13.57 min. The overall immediate success rate based on postoperative day 1 CT was 43.8%. Complications occurred in 14.9% of cases, and the mean length of hospital stay was 54.55 h. Stratifying patients according to GSS, success rate was inversely proportional to the calculus complexity: GSS1: 87.9%; GSS2: 62.1%; GSS3: 44.0%; and GSS4: 24.3% (P < 0.001). Higher GSS categories were significantly correlated with the number of puncture tracts (P < 0.001), operating time (P < 0.001), fluoroscopy time (P < 0.001), blood transfusion rate (P < 0.001), complications (P < 0.001) and length of stay (P < 0.001).

CONCLUSION

In a high-volume centre, PCNL was a reliable surgical technique, with low morbidity and short hospital stay. GSS was confirmed to be a very useful tool for predicting the outcomes of PCNL, and its use should be encouraged.

Rearrangement of the Guy's stone score improves prediction of stone-free rate after percutaneous nephrolithotomy

Objective

We propose a modification of the original Guy's Stone Score (GSS) to hold on 20 % of prognostic discrimination among groups which makes this score a more reliable resource for risk assessment in patients undergoing percutaneous nephrolithotomy (PCNL).

Material and methods

Historical cohort of 126 patients undergoing PCNL from December 2010 to November 2014 was included in the survey. Every patient was classified according to the original GSS. For the new classification of Guy Stone Score (GSS-M) all of the subgroups included in the scale were analyzed individually and then ranked from better to worst according to the postoperative stone- free rates (SFRs). This ranking led us to reclassify all the original subgroups, clustering them in three new categories according to their SFRs as subgroups of good, intermediate and poor prognosis, trying to achieve at least 20% of prognostic discrimination among the groups.

Results

Hundred and twenty-six PCNL procedures were evaluated, but only 124 were included for statistical analysis and classified based on SFR according to the GSS as follows: 76% for grade 1, 71% for grade 2, 55% for grade 3 and 20% for grade 4. The SFRs were also assessed for the GSS-M obtaining the following predictive values as 93%, 67% and 44% for the good, intermediate and poor prognostic groups, respectively. The prognostic difference among the GSS-M groups was always >20% (p<0.05).

Conclusion

The original GSS has limitations to predict SFR because of its poor discrimination power among prognostic groups. This rearrangement improves prediction of SFR and better discriminates risk groups in PCNL.

STONE score versus Guy's Stone Score - prospective comparative evaluation for success rate and complications in percutaneous nephrolithotomy

Purpose

The aim of the current study was to compare Guy's score and STONE score in predicting the success and complication rate of percutaneous nephrolithotomy (PCNL).

Materials and Methods

A total of 445 patients were included in the study between July 2015 and December 2016. The patients were given STONE score and Guy's Stone Score (GSS) grades based on CT scan done preoperatively and intra- and post-operative complications were graded using the modified Clavien grading system. The PCNL were done by a standard technique in prone positions.

Results

The success rate in our study was 86.29% and both the GSS and STONE score were significantly associated with a success rate of the procedure. Both the scoring systems correlated with operative time and postoperative hospital stay. Of the total cases, 102 patients (22.92%) experienced complications. A correlation between STONE score stratified into low, moderate, and high nephrolithometry score risk groups (low scores 4-5, moderate scores 6-8, high scores 9-13), and complication was also found (P = 0.04) but not between the GSS and complication rate (P = 0.054).

Conclusion

Both GSS and STONE scores are equally effective in predicting success rate of the procedure.

Can renal stone size and the use of the nephrolithometric system increase the efficacy of predicting the risk of failure of percutaneous nephrolithotripsy?

OBJECTIVE

to verify the association of success rate of percutaneous lithotripsy, Guy score and size of the stone.

METHODS

one hundred patients submitted to percutaneous nephrolithotripsy were evaluated. All stones were classified according to Guy Score. Patient free of stone was considered when residual fragments were ≤2mm.

RESULTS

according to guy Score, 54% were score 1 (Group 1), 18% score 2 (Group 2), 15% score 3 (Group 3), and 13% score 4 (Group 4). Success was observed in 77.77% in Group 1, 27.77% in group 2, 26.6% in Group 3, and 7.69% in Group 4. In patients with Guy score 1, there was statistical significance of prediction of free stone rate when evaluated according to the size of the stone. Among groups 2, 3 and 4 there was no statistical significance, but it was observed a trend in relation to stone size, the bigger the higher the chance of residual fragments.

CONCLUSION

nephrolithometry by Guy Score and size of the stone are single predictors of success of percutaneous nephrolithotripsy. Stone size may influence success rate of patients with Guy Score 1.

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.

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 Validation and Comparisons of the Scoring Systems for Predicting Percutaneous Nephrolithotomy Outcomes: A Single Center Experience with 506 Cases

BACKGROUND

To validate and compare the stone scoring systems (stone size [S], tract length [T], obstruction [O], number of involved calices [N], and essence or stone density [E] [S.T.O.N.E.], Guy's Stone Score [GSS], Clinical Research Office of the Endourological Society [CROES], and Seoul National University Renal Stone Complexity [S-ReSC]) used to predict postoperative stone-free status and complications after percutaneous nephrolithotomy (PCNL).

METHODS

A total of 567 patients who underwent PCNL for renal stones between January 2012 and August 2015 were included in the recent retrospective study. Sixty-one patients who had not done preoperative CT were excluded from the study. GSS, S.T.O.N.E., S-ReSC, and CROES nephrolithometry scores were calculated for each patient, and their potential association with stone-free status, operative and fluoroscopy time, and length of stay (LOS) was evaluated. Postoperative complications were graded according to the modified Clavien classification, and the correlation of scoring systems with postoperative complications was also investigated.

RESULTS

The mean CROES, S.T.O.N.E., GSS, and S-ReSC scores were 203.7 ± 59.8, 7.52 ± 1.8, 2.08 ± 0.9, and 3.35 ± 2.2, respectively. The overall stone-free rate was 77.9%. All scoring systems were significantly correlated with stone-free status and operation time. While GSS, S.T.O.N.E., and CROES systems were significantly correlated with complication rates (CR), S-ReSC score failed to predict CR. All scoring systems except S.T.O.N.E. were significantly correlated with LOS. CROES and S-ReSC scores were predictive of estimated blood loss (EBL), while GSS and S.T.O.N.E. failed to predict EBL.

CONCLUSIONS

Recent study demonstrated that S.T.O.N.E., GSS, CROES, and S-ReSC scoring systems could effectively predict postoperative stone-free status. Although S-ReSC scoring system failed to predict CR, the rest three scoring systems were significantly correlated with postoperative CR.

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.

Prediction of Pediatric Percutaneous Nephrolithotomy Outcomes Using Contemporary Scoring Systems

PURPOSE

We evaluate the applicability of contemporary percutaneous nephrolithotomy scoring systems in pediatric patients and compare their predictive power regarding postoperative outcomes.

MATERIALS AND METHODS

We retrospectively analyzed the records of 125 children who were diagnosed with renal calculi and underwent percutaneous nephrolithotomy between March 2011 and April 2016. Predictive scores, which consisted of Guy's Stone Score, S.T.O.N.E. (stone size, tract length, obstruction, number of involved calyces and essence/stone density) nephrolithometry and CROES (Clinical Research Office of the Endourological Society) nomogram, were calculated for all patients included in the study. Patient demographics, stone-free rate and complications were all analyzed and are reported.

RESULTS

Median Guy's Stone Score was 2 (IQR 2 to 3) in patients with residual stones (group 1) and 2 (1 to 2) in those who were stone-free (group 2). Median respective CROES nomogram scores were 215 (IQR 210 to 235) and 257 (240 to 264), and S.T.O.N.E. nephrolithometry scores were 8 (7 to 9) and 5 (5 to 6, all p <0.0001). S.T.O.N.E. score demonstrated the greatest accuracy in predicting stone-free rate. Guy's Stone Score was significantly correlated with complications but the CROES and S.T.O.N.E. scores were not significantly correlated with complications.

CONCLUSIONS

The scoring systems analyzed could be used to predict success of percutaneous nephrolithotomy in the pediatric setting. However, further studies are needed to formulate modifications for use in children. The main variables in the scoring systems, ie stone burden, tract length and case volume, were measured using records from adult patients. Besides these variables, the relatively small pelvicalyceal system and higher incidence of anatomical malformations in children could potentially affect percutaneous nephrolithotomy outcomes.

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.

How practical is the application of percutaneous nephrolithotomy scoring systems? Prospective study comparing Guy's Stone Score, S.T.O.N.E. score and the Clinical Research Office of the Endourological Society (CROES) nomogram

Objective

To prospectively compare the Guy’s Stone Score (GSS), S.T.O.N.E. [stone size (S), tract length (T), obstruction (O), number of involved calices (N), and essence or stone density (E)] score and the Clinical Research Office of the Endourological Society (CROES) nephrolithometric nomogram to predict percutaneous nephrolithotomy (PCNL) success rate and assess the correlation with perioperative complications.

Patients and methods

We prospectively evaluated all consecutive PCNL patients at our institute between 1 November 2013 and 31 May 2015. The above scoring systems were applied to preoperative non-contrast computed tomography and the practical difficulties in such applications were noted. Perioperative complications and the stone-free rate (SFR) were also recorded. Receiver operating characteristic curves were drawn and the areas under curves were compared and appropriate statistical analysis done.

Results

In all, 48 renal units were included in the study. The overall SFR was 62.2%. The presence of staghorn stones (β = 27.285, 95% confidence interval 1.19–625.35; P = 0.039) was the only significant variable associated with the residual stones on multivariate analysis. Stone-free patients had significantly lower median GSS (2 vs 4) and S.T.O.N.E. scores (6 vs 10) and higher median CROES scores (83% vs 63%) (all P < 0.001) compared to residual-stone patients. All scoring systems were significantly associated with SFR (all P < 0.001). There was no significant difference in the areas under curves of the scoring systems (0.858, 0.923, and 0.931, respectively). Furthermore, all scoring systems had weak correlations with Clavien–Dindo classified complications (r = 0.29, P = 0.045; r = 0.40, P = 0.005 and r = −0.295, P = 0.04, respectively). We found no standardisation for the measurement of stone dimensions, tract length, Hounsfield units, and staghorn definition.

Conclusions

All scoring systems equally predicted SFR and had a weak correlation with Clavien–Dindo complications. Standardisation is needed for the variables in which they have been found deficient.

Residual stones after percutaneous nephrolithotomy: comparison of intraoperative assessment and postoperative non-contrast computerized tomography

OBJECTIVES

To compare the intraoperative surgeon perspective for detection of residual fragments (RFs) after percutaneous nephrolithotomy (PNL) with postoperative NCCT.

METHODS

A prospective study of adult patients who underwent PNL between March and September 2014 was conducted. Stone complexity was evaluated using the Guy's stone score (GSS). All patients were evaluated by pre- and postoperative NCCT. After the procedure, the surgeon had been asked whether there were residual stones or not. The sensitivity, specificity and predictive values were tested against postoperative NCCT. Predictors of accurate intraoperative assessment were determined using univariate and multivariate statistical analyses.

RESULTS

The study included 306 consecutive patients. The surgeons reported no residual stones in 236 procedures; of whom 170 (72%) were reported stone-free by NCCT. On the other hand, 65 out of 70 procedures (93%) reported with residual stones by the surgeons were true by NCCT. The sensitivity was 50% and the NPV was 72%, while the specificity was 97% and the PPV was 93%. On multivariate analysis, only lower GSS (p < 0.001) was independently associated with true negative surgeon opinion.

CONCLUSIONS

Although there was a high surgeon ability to detect post-PNL residual stones, postoperative imaging is mandatory because of the high false negative rates and low NPV. The surgeon opinions can be judged only in stones with lower GSS. The NPV could be enhanced if a consistent definition of clinically significant RFs is introduced.

Guy's Stone Score (GSS) Based on Intravenous Pyelogram (IVP) Findings Predicting Upper Pole Access Percutaneous Nephrolithotomy (PCNL) Outcomes

Objective. To predict the success rate and complications following percutaneous nephrolithotomy via the upper pole using the Guy's Stone Score (GSS) based on the findings of a preoperative intravenous pyelogram (IVP). Patients and Methods. Two hundred and twenty-seven renal operations, which were carried out using PCNL via the upper pole, were classified according to the GSS assigned. Any complications were classified according to the Clavien classification. The success rates and incidence of any complications were compared between each GSS. Results. The immediate success rates were 87.50% of GSS1, 71.43% of GSS2, 53.62% of GSS3, and 38.46% of GSS4, P < 0.01. There were statistically significant differences between the groups in stone size, overall immediate success rate, operative time, number of access tracts, and frequency of tubeless PCNL. Major complications (a Clavien score of 3-5) were significantly higher in the cases with a higher GSS. Conclusion. A GSS based on an IVP is a simple and reliable tool in predicting the success rate and possible complications following upper pole access PCNL.

Effects of Parenchymal Thickness and Stone Density Values on Percutaneous Nephrolithotomy Outcomes

BACKGROUND It is unclear whether parenchymal thickness (PT), in combination with stone density measured by Hounsfield Units (HU), affects stone-free rates after PCNL. The aim of the present study was to investigate the relationship between PT in combination with stone density values and the outcomes of PCNL. MATERIAL AND METHODS From 2009 to 2014, data from 216 PCNL patients were prospectively analyzed. In total, 120 patients were included in the study. Using NCCT images, stone burden, stone localization, stone density as HU values, PT, and operative-postoperative parameters were recorded. RESULTS Stone localization, stone type, stone burden, and presence of hydronephrosis were statistically significant factors affecting stone-free status (p<0.001, p<0.001, p<0.01, and p<0.01, respectively). The stone-free rate in patients with thicker renal parenchyma was higher than in patients with lower parenchymal thickness (p<0.01). No correlation was detected between stone density and success rate (p>0.05). Drop in Hb (%) was only correlated with parenchymal thickness (p<0.01). In univariate analyses, factors that affected blood transfusion requirement were PT, BMI, and operative times (p<0.01, p<0.05, and p<0.05, respectively). CONCLUSIONS Stone location, stone burden, and presence of hydronephrosis detected with NCCT were factors affecting PCNL outcome. Stone density values did not correlate with the rate of bleeding or success of PCNL. PT measured by NCCT may predict bleeding and may guide surgeons in determining preoperative blood requirements. The outcome of PCNL appeared to be better in patients with thicker renal parenchyma and should be taken into consideration in the clinical evaluation of patients undergoing PCNL.

The challenge of cystine and struvite stone formers: clinical, metabolic and surgical assessment

Purpose:

To compare the clinical, metabolic, and calculi characteristics of cystine and struvite stone patients after percutaneous nephrolithotripsy (PCNL).

Material and Methods:

Between January/2006-July/2013, 11 cystine stone patients were treated in our clinic. Of those, 3 were excluded due to incomplete follow-up. Eight cystine stone patients (2 with bilateral disease; 10 renal units-RU) were considered for further analysis. A cohort of 8 struvite stone formers (10RU) was matched having the same age, gender, body mass index (BMI) and Guys stone score. Analyzed parameters comprised demographic data, serum/urinary metabolic evaluation and surgical outcomes.

Results:

Both groups had 6 female patients. Groups were similar in regards to age, gender, BMI, stone burden, and serum creatinine (p=NS). All patients had PCNL as the first surgical treatment modality. Stone free rate (SFR) after the first PCNL tended to be lower (0%) in the cystine compared to the struvite group (40%)(p=0.08). Final SFR after secondary procedures increased to 70% in cystine and 80% in struvite patients (p=1.0); mean number of procedures to achieve stone free status was higher in the first group (3.57 vs. 2.0;p=0.028). Hypocitraturia was found in all patients, but struvite cases presented with lower mean urinary citrate levels (p=0.016). Other common abnormalities were elevated urinary pH (cystine 75% and struvite 62.5%;p=1.0) and low urinary volume (62.5%,37.5%;p=0.63).

Conclusion:

Multiple interventions and suboptimal stone free rates are trait of the significant stone burden of struvite and cystine patients. Underlying metabolic abnormalities characterized by increased urinary pH, hypocitraturia and low urinary volume are often encountered in both populations.

Implications of different nephrolithometry scoring systems on clinical practice of endourologists: An international web-based survey

OBJECTIVES

To assess the implications of different nephrolithometry scoring systems (NLSS) on clinical practice of endourologists to predict stone-free status (SFS) after percutaneous nephrolithotomy (PCNL).

METHODS

A web-based survey was sent to members of the Endourological Society. Demographic and practice pattern data were collected. Multiple-choice and open-ended questions were used to assess awareness about the NLSS and their authentic use in clinical practice. Surgeon preferences and limitations of NLSS and how to overcome them were asked.

RESULTS

In all, there were 162 responses, including 17 (10.5%) respondents who were not aware of NLSS. Most respondents (82.1%) denied the efficacy of NLSS in predicting SFS after PCNL. Of 145 respondents who were aware of NLSS, 85.5% did not use them in clinical practice. Endourologists aged 40-60 years (P < 0.001), in practice for 10-20 years (P = 0.003), those performing 100-200 PCNLs/year (P = 0.02), and those from North America (P < 0.001) seemed to use NLSS more frequently. In all, 50% of respondents preferred not to use any NLSS, while 29% chose the S.T.O.N.E followed by the Guy's Stone Score (10.3%) and The Clinical Research Office of the Endourology Society (CROES) nomogram (8.3%). Inconsistency and variability among different NLSS were the main drawbacks reported by 82% of 89 respondents. The need for high-level evidence for NLSS through direct randomised prospective comparison was recommended by 24.8% of respondents who answered that question.

CONCLUSION

There is a lack of compliance and acceptance of different NLSS in clinical practice among endourologists. Inconsistency and inaccuracy in predicting SFS after PCNL limits their incorporation into clinical practice. However, the results of this study might not be generalisable due to the selection bias resulting from the geographical distribution of the respondents and the heterogeneity in surgical expertise. Therefore, randomised prospective direct comparisons and validation of these systems are recommended.

Prediction of stone-free status and complication rates after tubeless percutaneous nephrolithotomy: a comparative and retrospective study using three stone-scoring systems and preoperative parameters

PURPOSE

To investigate the factors predictive of surgical outcomes of tubeless percutaneous nephrolithotomy (TPCNL) and to compare the predictability and accuracy of the Guy's stone score, S.T.O.N.E. nephrolithometry, and CROES nomogram.

PATIENTS AND METHODS

We reviewed retrospectively the surgical outcomes recorded consecutively and imaging data of preoperative computed tomography scans of 141 patients who had undergone TPCNL from June 2012 to October 2015. Guy's, S.T.O.N.E., and CROES stone-scoring systems (SSSs) and other prognostic factors were assessed using univariate and multivariate statistical analyses.

RESULTS

The initial stone-free and complication rates after TPCNL were 78.7 (111/141) and 17.0 % (24/141). On univariate analysis, all three scoring systems were identified as significant factors in terms of stone-free rate (SFR). The multivariate logistic regression analysis showed that the Guy's stone score and stone burden ≥385 mm² had significant correlations with stone-free status [odds ratios (OR) = 3.220, p = 0.001 and OR = 6.451, p = 0.002, respectively]. Guy's stone score (OR = 1.879, p = 0.013) was an independent risk factor for the development of complications. The area under the receiver operating characteristic (ROC) curves for the Guy's, S.T.O.N.E., and CROES SSSs and stone burden showed good results (0.821, 0.816, 0.820, and 0.800, respectively). Pairwise comparison of ROC curves showed that there was no significant difference between each final score and stone burden.

CONCLUSIONS

Of the three scoring systems, Guy's stone score was the only significant predictive factor for SFR and complication rates after TPCNL in the multivariate logistic regression analysis. Stone burden was significantly associated with a postoperative stone-free status (SFS).