Stone Burden Measurement by 3D Reconstruction on Noncontrast Computed Tomography Is Not a More Accurate Predictor of Stone-Free Rate After Percutaneous Nephrolithotomy Than 2D Stone Burden Measurements

A machine learning approach using stone volume to predict stone-free status at ureteroscopy

INTRODUCTION

To develop a predictive model incorporating stone volume along with other clinical and radiological factors to predict stone-free (SF) status at ureteroscopy (URS).

MATERIAL AND METHODS

Retrospective analysis of patients undergoing URS for kidney stone disease at our institution from 2012 to 2021. SF status was defined as stone fragments < 2 mm at the end of the procedure confirmed endoscopically and no evidence of stone fragments > 2 mm at XR KUB or US KUB at 3 months follow up. We specifically included all non-SF patients to optimise our algorithm for identifying instances with residual stone burden. SF patients were also randomly sampled over the same time period to ensure a more balanced dataset for ML prediction. Stone volumes were measured using preprocedural CT and combined with 19 other clinical and radiological factors. A bagged trees machine learning model with cross-validation was used for this analysis.

RESULTS

330 patients were included (SF: n = 276, not SF: n = 54, mean age 59.5 ± 16.1 years). A fivefold cross validated RUSboosted trees model has an accuracy of 74.5% and AUC of 0.82. The model sensitivity and specificity were 75% and 72.2% respectively. Variable importance analysis identified total stone volume (17.7% of total importance), operation time (14.3%), age (12.9%) and stone composition (10.9%) as important factors in predicting non-SF patients. Single and cumulative stone size which are commonly used in current practice to guide management, only represented 9.4% and 4.7% of total importance, respectively.

CONCLUSION

Machine learning can be used to predict patients that will be SF at the time of URS. Total stone volume appears to be more important than stone size in predicting SF status. Our findings could be used to optimise patient counselling and highlight an increasing role of stone volume to guide endourological practice and future guidelines.

Treatment of ureteropelvic junction obstruction in patients with renal calculi via laparoscopic pyeloplasty and flexible vacuum-assisted ureteral access sheath ureteroscopy: a multicenter retrospective observational study

BACKGROUND

Ureteropelvic junction obstruction (UPJO) is a common obstructive disease of the urinary tract. UPJO patients commonly exhibit coexistent renal calculi. The main aim of therapy is to relieve the obstruction and remove the stones at the same time.

METHODS

This retrospective study included 110 patients diagnosed with UPJO coexisting with multiple renal calculi at Shanxi Bethune Hospital and the First Hospital of Shanxi Medical University between March 2016 and January 2022. Patients were divided according to the methods used for dealing with UPJO and renal calculi. In Group A, patients underwent traditional open pyeloplasty and pyelolithotomy. In Group B, patients underwent percutaneous nephrolithotomy first and then laparoscopic pyeloplasty. In Group C, patients underwent flexible cystoscopy to remove stones and then laparoscopic pyeloplasty. In Group D, patients underwent flexible vacuum-assisted ureteral access sheath (FV-UAS)assisted flexible ureteroscopy (f-URS) and underwent laparoscopic pyeloplasty. The stones were broken up using a holmium laser. The pyeloplasty success rate, stone clearance rate, operation time, bleeding amount, complication occurrence rate, postsurgical pain, length of stay, and hospitalization cost were compared between the groups. The follow-up period was at least 2 years.

RESULTS

The use of f-URS and the FV-UAS, significantly increased the renal stone clearance rate and significantly reduced the complication incidence and operation time in UPJO patients with multiple coexisting renal calculi.

CONCLUSIONS

Laparoscopic pyeloplasty combined with f-URS and FV-UAS is safe and effective for treating UPJO in patients complicated by renal caliceal stones.

TRIAL REGISTRATION

Retrospectively registered.

Comparison of ureteral stone measurements for predicting the efficacy of a single session of extracorporeal shockwave lithotripsy: one-, two-, and three-dimensional computed tomography measurements

The objective of this study was to compare the value of one-, two- and three-dimensional computed tomography (CT) measurements for predicting the efficacy of a single session of extracorporeal shock wave lithotripsy (ESWL) in patients with a single ureteral stone. A total of 165 patients were included based on the inclusion and exclusion criteria. Different models were constructed using a combination of patients' clinical data and measurements obtained by manual sketching and automated extraction software. Multivariate logistic regression was used to develop the models. Receiver operating characteristic curves were used to assess the performance of the models. There was good interobserver agreement for all measurements in different dimensions (P < 0.001). We also found that hydronephrosis, the largest diameter, the largest area, volume, and mean CT value were significantly greater in the failure group than in the success group (P < 0.01). Furthermore, all sizes and CT measurement values were found to be independent predictors for predicting efficacy after one session of ESWL (P < 0.05). In addition, the multivariate logistic analysis showed that the area under the curve (AUC) for two-dimensional and three-dimensional measurements was superior to that of one-dimensional measurement (P < 0.01). However, when size alone was included as a measurable predictor, there was no significant difference in the AUC among the one-, two-, and three-dimensional measurements (P > 0.05). In summary, after adjusting for clinical data, two- and three-dimensional measurements combining ureteral stone size and CT values were found to be the best predictors of ESWL efficacy, and software-based three-dimensional measurements should be considered to avoid interobserver variability in clinical practice.

How to estimate stone volume and its use in stone surgery: a comprehensive review

OBJECTIVE

Current interventional guidelines refer to the cumulative stone diameter to choose the appropriate surgical modality (ureteroscopy [URS], extracorporeal shockwave lithotripsy [ESWL] and percutaneous nephrolithotomy [PCNL]). The stone volume (SV) has been introduced recently, to better estimate the stone burden. This review aimed to summarize the available methods to evaluate the SV and its use in urolithiasis treatment.

MATERIAL AND METHODS

A comprehensive review of the literature was performed in December 2022 by searching Embase, Cochrane and Pubmed databases. Articles were considered eligible if they described SV measurement or the stone free rate after different treatment modalities (SWL, URS, PCNL) or spontaneous passage, based on SV measurement. Two reviewers independently assessed the eligibility and the quality of the articles and performed the data extraction.

RESULTS

In total, 28 studies were included. All studies used different measurement techniques for stone volume. The automated volume measurement appeared to be more precise than the calculated volume. In vitro studies showed that the automated volume measurement was closer to actual stone volume, with a lower inter-observer variability. Regarding URS, stone volume was found to be more predictive of stone free rates as compared to maximum stone diameter or cumulative diameter for stones >20 mm. This was not the case for PCNL and SWL.

CONCLUSIONS

Stone volume estimation is feasible, manually or automatically and is likely a better representation of the actual stone burden. While for larger stones treated by retrograde intrarenal surgery, stone volume appears to be a better predictor of SFR, the superiority of stone volume throughout all stone burdens and for all stone treatments, remains to be proven. Automated volume acquisition is more precise and reproducible than calculated volume.

Development of a novel mesh model to define a new index "amount of stone" to evaluate calculus and predicting the lithotripsy time

OBJECTIVE

Develop a mesh model to define a new "index amount of stone" to evaluate calculus and predict lithotripsy time.

METHODS

The stones were divided into target units with diameter of 5 mm by the mesh from x, y and z directions, and the cross-sectional areas between units were calculated as amount of stone as a new index to evaluate calculus. Design a prospective study with 112 cases of percutaneous nephrolithotomy to verify the reliability of this index, and to compare the accuracy of the quantity, volume and maximum diameter of stones in predicting the time of lithotripsy.

RESULTS

Amount of stone (Q) is reliable. The lithotripsy time was significantly correlated with the amount of stone, volume and maximum diameter of the stone (p < 0.01). The three regression equations were valid. The linear fit in the amount group was larger than that in the volume group, and further larger than that in the maximum diameter group, with R2 values of 0.716, 0.661 and 0.471, respectively.

CONCLUSIONS

It is more accurate and convenient to use amount of stone to evaluate calculus, which can be used to predict the lithotripsy time.

Classification and clinical significance of the posterior group of renal calyces

To study the anatomical orientation of the posterior group of calyces based on reconstructed images of computerized tomography urography (CTU) and provide a novel classification with its clinical significance. Clinical data of a total of 1321 patients, who underwent CTU examination in our hospital were retrospectively analyzed. Among these, a total of 2642 3-dimensional reconstructed images of CTU scans were considered in this study. Based on the morphology of the renal calyces and the influence on the establishment of surgical access, the posterior group renal calyces are classified into 3 major types including pot-belly type, classically branched and elongated branched. The classically branched type is further classified into 3 sub-types: a, b and c, based on the association of minor calyces of the posterior group to the major calyces. Type a is derived from 1 group of major calyces only, type b is derived from 2 groups of major calyces simultaneously, and type c is derived from 3 groups of major calyces simultaneously. Statistical findings revealed that all kidneys possess posterior group calyces. The percentage of occurrence of pot-belly type, classically branched and elongated branched is 8.06%, 73.13%, and 18.81%, respectively. The anatomical typing of the classical branching type occurred in 19.36%, 68.17%, and 12.47% for types a, b, and c, respectively. In this study, the posterior group calyces were found to be present across all patients. The posterior group calyces were highest in the classical branching type, of which anatomical typing was highest in type b. The typing of the posterior group of calyces could provide an anatomical basis for percutaneous nephrolithotomy (PCNL) puncture from the posterior group.

Comparison of Superpulse Thulium Fiber Laser vs Holmium Laser for Ablation of Renal Calculi in an In Vivo Porcine Model

Introduction and Objectives: We sought to compare the effectiveness and efficiency of the superpulse thulium fiber laser (sTFL to the holmium: yttrium-aluminum-garnet [Ho:YAG] laser for ureteroscopic "dusting" of implanted renal stones in an in vivo porcine model. Methods: Twenty-four porcine kidneys (12 juvenile female Yorkshire pigs) were randomized to Ho:YAG or sTFL treatment groups. Canine calcium oxalate stones were scanned with computed tomography to calculate stone volume and stone density; the stones were randomized and implanted into each renal pelvis via an open pyelotomy. In all trials, a 14F, 35 cm ureteral access sheath was placed. With a 9.9F dual lumen flexible ureteroscope, laser lithotripsy was performed using dusting settings: Ho:YAG 200 μm laser fiber at 16 W (0.4 J, 40 Hz) or sTFL 200 μm laser fiber at 16 W (0.2 J, 80 Hz). Lithotripsy continued until no fragments over 1 mm were observed. No stone basketing was performed. Throughout the procedures, intrarenal and renal pelvis temperatures were measured using two percutaneously positioned K-type thermocouples, one in the upper pole calyx and one in the renal pelvis. After the lithotripsy, the ureteropelvic junction was occluded, the kidneys were bivalved, and all residual fragments were collected, dried, weighed, and then measured with an optical laser particle sizer. Results: Implanted stones were similar in volume and density in both groups. Intraoperative collecting system temperatures were similar for both groups (all <44°C). Compared to Ho:YAG, sTFL ablated stones faster (9 vs 27 minutes, p < 0.001) with less energy expenditure (8 vs 26 kJ, p < 0.001), and a greater stone clearance rate (73% vs 45%, p = 0.001). After sTFL lithotripsy, 77% of the remaining fragments were ≤1 mm vs 17% of fragments ≤1 mm after Ho:YAG treatment (p < 0.001). Conclusions: In an in vivo porcine kidney, using dusting settings, sTFL lithotripsy resulted in shorter ablation times, higher stone clearance rates, and markedly smaller stone fragments than Ho:YAG lithotripsy.

Imaging in stone diagnosis and surgical planning

PURPOSE OF REVIEW

Radiological imaging techniques and applications are constantly advancing. This review will examine modern imaging techniques in the diagnosis of urolithiasis and applications for surgical planning.

RECENT FINDINGS

The diagnosis of urolithiasis may be done via plain film X-ray, ultrasound (US), or contrast tomography (CT) scan. US should be applied in the workup of flank pain in emergency rooms and may reduce unnecessary radiation exposure. Low dose and ultra-low-dose CT remain the diagnostic standard for most populations but remain underutilized. Single and dual-energy CT provide three-dimensional imaging that can predict stone-specific parameters that help clinicians predict stone passage likelihood, identify ideal management techniques, and possibly reduce complications. Machine learning has been increasingly applied to 3-D imaging to support clinicians in these prognostications and treatment selection.

SUMMARY

The diagnosis and management of urolithiasis are increasingly personalized. Patient and stone characteristics will support clinicians in treatment decision, surgical planning, and counseling.

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.

Assessment of Three-Dimensional Reconstruction in Percutaneous Nephrolithotomy for Complex Renal Calculi Treatment

Introduction: Three-dimensional (3D) reconstruction is a novel imaging technique widely used to improve surgical operations. Some studies have identified its role in Urology for percutaneous nephrolithotomy (PCNL). Objective: To explore the potential benefits of 3D reconstruction technology in PCNL for complex renal calculi treatment. Methods: A retrospective study involving 139 patients with complex kidney stones who underwent PCNL was conducted between September 30, 2018, to September 30, 2019. Group A patients (72) underwent the 3D reconstruction technique before PCNL, while group B (67) did not. The operation time, the duration of the hospital stay, the puncture accuracy, the decrease in hemoglobin concentration, the stone clearance rate, and the postoperative complications were noted and compared between the two groups. Results: The initial stone clearance rates 2 weeks after PCNL were 81.9 and 64.2% in groups A and B, respectively (P < 0.05). The first-time puncture success rates were 87.5 and 47.8 % in groups A and B, respectively (P < 0.05). Group A had a shorter operation time than group B (62 vs. 79 min, P < 0.05). Besides, the 3D reconstructive technique-assisted patients (91.7%) had no or mild complications, compared with (74.6%) group B patients. There was no significant difference in hemoglobin decline and hospital stay between the two groups. Conclusions: The 3D reconstruction technology is an effective adjunct to PCNL in the complex renal calculi treatment.