Size is Not Everything That Matters: Preoperative CT Predictors of Stone Free After RIRS

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.

Residual fragment size following retrograde intrarenal surgery: a critical evaluation of related variables

Given the limited data on the predictive factors of residual kidney stone size after flexible ureteroscopy (fURS), this study aims to investigate the variables affecting residual stone size. The medical records of 642 patients without complications being treated for kidney stones with fURS between July 2014 and May 2022 were reviewed retrospectively, and the information of the 170 patients in whom residual stones were found was recorded. In addition to patient-specific factors and stone characteristics, length of postoperative hospital stay, postoperative fever, and preoperative antiaggregant use were evaluated. Of the 170 patients ultimately included in the study. The mean age was 51.56 (± 14.70). The mean stone size was 14.01 mm (± 5.75), the mean residual stone size was 7.04 mm (± 2.51), and the mean stone density was 829 Hounsfield units (± 395.06). The mean infundibulopelvic angle (IPA) was 49.37º (± 15.37), and 41.2% of the stones were non-opaque. The mean parenchymal thickness was 22.88 mm (± 5.55). 34 patients were on antiaggregant therapy. Preoperative stone size increases in stone density and decreases in IPA were found to be correlated with increase residual stone size (p < 0.001, p < 0.001, and p < 0.001, respectively). In addition, larger residual stones were observed after the fURS procedure in patients using anticoagulants and those without hydronephrosis (p = 0.02 and p = 0.016, respectively). Use of reliable predictive factors to forecast residual stone size after fURS may help to inform those treated and enable urologists to design rational surgical strategies.

External validation of the current scoring systems and derivation of a novel scoring system to predict stone free rates after retrograde intrarenal surgery in patients with cumulative stone diameter of 2-4 cm

OBJECTIVE

Our primary aim is to perform the external validation of the current scoring systems in predicting stone-free status (SFS) after retrograde intrarenal surgery (RIRS) for renal stones 2-4 cm and develop a novel scoring system by re-examining possible predictive factors related to SFS.

METHODS

Patients who underwent RIRS due to renal stones with a cumulative stone diameter of 2-4 cm between January 2017 and March 2021 were retrospectively screened. Residual stones ≤2 mm were defined as clinically insignificant, and these cases were considered to have SFS. Possible predictive factors related to SFS were examined using the multivariate logistic regression analysis. A nomogram and a scoring system were developed using independent predictive variables. The prediction ability of the previous and the new scoring system were evaluated with the ROC analysis.

RESULTS

The existing scoring systems were found to be insufficient in predicting SFS (AUC < 0.660 for all). The independent predictors of SFS were identified as stone surface area (OR: 0.991, p < 0.001), stone density (OR: 0.998, p < 0.001), number of stones (OR: 0.365, p = 0.033), and stone localization (p = 0.037). Using these predictive markers, a new scoring system with a score ranging between 4 and 15 was developed. The AUC value for this scoring system was 0.802 (0.734-0.870).

CONCLUSION

The RUSS, S-ReSC and R.I.R.S. scoring systems and Ito's nomogram failed to predict SFS in stones >2 cm. The SFS predictive ability of our new scoring system was higher in >2 cm stones compared to the other scoring systems.

International Alliance of Urolithiasis guideline on retrograde intrarenal surgery

OBJECTIVES

To set out the second in a series of guidelines on the treatment of urolithiasis by the International Alliance of Urolithiasis that concerns retrograde intrarenal surgery (RIRS), with the aim of providing a clinical framework for urologists performing RIRS.

MATERIALS AND METHODS

After a comprehensive search of RIRS-related literature published between 1 January 1964 and 1 October 2021 from the PubMed database, systematic review and assessment were performed to inform a series of recommendations, which were graded using modified GRADE methodology. Additionally, quality of evidence was classified using a modification of the Oxford Centre for Evidence-Based Medicine Levels of Evidence system. Finally, related comments were provided.

RESULTS

A total of 36 recommendations were developed and graded that covered the following topics: indications and contraindications; preoperative imaging; preoperative ureteric stenting; preoperative medications; peri-operative antibiotics; management of antithrombotic therapy; anaesthesia; patient positioning; equipment; lithotripsy; exit strategy; and complications.

CONCLUSION

The series of recommendations regarding RIRS, along with the related commentary and supporting documentation, offered here should help provide safe and effective performance of RIRS.

The effect of Trendelenburg position on outcomes of retrograde intrarenal surgery for medium sized renal pelvis stones

Aim: To compare safety and efficiency between Trendelenburg position retrograde intrarenal surgery (tRIRS) and conventional position retrograde intrarenal surgery (cRIRS) in the management of renal pelvis stones 10-20 mm in size. Material and Method: From September 2018 to September 2019, the patients undergoing RIRS for single renal stones between 10-20 mm were included in the study prospectively. Patients were divided into two groups randomly. First group of patients were positioned completely parallel to the ground (cRIRS), second group were positioned with Trendelenburg (tRIRS). Success was evaluated at end of 3rd months by non-contrast enhanced tomography. Stones that smaller than 4 mm were accepted as clinical insignificant residual fragment. Complications was classified according to Clavien, class 2 or more complications were recorded. Results: Totally 100 patients were included to final analyze. Patients’ age, gender, stone side and mean stone surface area were similar between groups. Success rate was higher in tRIRS group (90% vs 72% p=0.022). Mean operation time was lower (41.8 vs 58.2 min. p

External validation of efficacy and reliability of different retrograde intrarenal surgery (RIRS) scoring systems for pediatric nephrolithiasis

INTRODUCTION

Retrograde Intrarenal Surgery (RIRS) is one of minimally invasive procedures for pediatric upper urinary stones. However, a RIRS predictive system for children to evaluate postoperative stone free rate (SFR) is still unavailable.

OBJECTIVE

The aim of this study is to validate the efficacy and reliability of different RIRS scoring systems for children.

STUDY DESIGN

We collected clinical data of 137 pediatric patients treated with RIRS in our center between 2014 and 2021. All the predictors were acquired by preoperative non-contrast CT or CT urography. Receiver Operative Curve (ROC) and Area Under Curve (AUC) were showed to compare the predictive power of different models.

RESULTS

A total of 162 RIRS procedures were performed for these 137 pediatric patients. Median surgical duration, irrigation volume and hospitalization were 30 (20, 40) min, 500 (300, 1000) ml and 6 (4, 7) days, respectively. Overall SFR and complication rate was 79.6% (129/162) and 29.2% (40/137), respectively. Significant difference was detected between non-stone free group and stone free group in terms of stone complexity (p < 0.001), cumulative stone sizes [2.3 (2.0, 3.5) cm vs. 1.5 (1.0, 2.0) cm, p < 0.001], RUS groups (p < 0.001), S-ReSC groups (p < 0.001) and RIRS nomogram score [10 (8, 12) vs. 23 (18, 25), p < 0.001]. Among them, RIRS nomogram presented with the maximum AUC values in comparison with the other two systems (RUS: 0.944 vs. 0.874, p = 0.001; S-ReSC: 0.944 vs. 0.808, p < 0.001).

DISCUSSION

We reported the largest sample size of pediatric patients treated with RIRS in our center. Similar with previous studies, RIRS is an efficacious and safe option for pediatric patients. RIRS nomogram showed the best predictive outcome due to the inclusion of multiple parameters, but an innovative predictive system based on pediatric clinical data is warranted in the future.

CONCLUSION

Among the three scoring systems, RIRS nomogram showed the most optimal predictive power of postoperative SFR for pediatric patients.

Comparison of the outcomes of flexible ureteroscopy and mini-percutaneous nephrolithotomy for the treatment of kidney stones: a matched-pair analysis

OBJECTIVE

Mini-percutaneous nephrolithotomy is a recent advancement in the field of kidney stone treatment; however, its role has not been completely established. We aimed to compare the outcomes of initial Mini-percutaneous nephrolithotomy and flexible ureteroscopy.

METHODS

A retrospective review of consecutive mini-percutaneous procedures was performed. Inclusion criteria were as follows: all percutaneous nephrolithotomy procedures performed with an access sheath up to 24Fr, kidney stone burdens up to 1550 mm3; and the presence of postoperative computed tomography (for control). The data collected for Mini-percutaneous nephrolithotomy procedures were paired 1:2 with patients treated with flexible ureteroscopy for stones between 100 and 1550 mm3, and with postoperative computed tomography for control. A 14Fr Mini-percutaneous nephrolithotomy set was used. The stone-free rate was defined as the absence of fragments on the control computed tomography, whereas success was limited to 2-mm residual fragments. Statistical analysis was performed using SPSS version 19.

RESULTS

A total of 63 patients met the inclusion criteria (42 with flexible ureteroscopy and 21 with mini-percutaneous nephrolithotomy). Demographic data were comparable. The stone-free rate and success were similar between the groups (76.2 vs. 66.7%, p=0.42 and 90.5 vs. 85.7%, p=0.57). The complication rate was also similar (26.1 vs. 9.6%, p=0.188), but Mini-percutaneous nephrolithotomy had longer hospitalization and fluoroscopy time (p=0.001 in both).

CONCLUSIONS

Our initial study of Mini-percutaneous nephrolithotomy showed that it is a promising procedure, with outcomes similar to flexible ureteroscopy, but with higher inpatient numbers and fluoroscopy times. A larger study population size and better equipment may improve the outcomes of mini-percutaneous nephrolithotomy.

Does previous standard percutaneous nephrolithotomy impair retrograde intrarenal surgery outcomes?

PURPOSE

The objective of this study is to evaluate the impact of a previous standard percutaneous nephrolithotomy (PCNL) on the outcomes of retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

Outcomes of RIRS performed from January 2017 to January 2020 in adult patients with residual stone fragments ≤20mm after a standard PCNL (Post-PCNL) and symptomatic adult patients with kidney stones ≤20mm (Control) were prospectively studied. Stone-free rate (SFR) was evaluated on a postoperative day 90 non-contrast computed tomography. Surgical complications based on Clavien-Dindo classification during the 90 days of follow-up were recorded.

RESULTS

Outcomes of 55 patients and 57 renal units of the post-PCNL group were compared to 92 patients and 115 renal units of the control group. SFR was lower in post-PCNL group than in control (28/57, 49.1% vs. 86/115, 74.8%, p < 0.001). Overall complications were more frequent in post-PCNL group (p=0.004). Infundibula strictures were identified and incised with laser in 15/57 (26.3%) renal units of the post-PCNL group. Thirteen renal units had infundibulum stricture at the site of previous percutaneous tract (13/15; 86.7%, p=0.004) and one renal unit had three infundibula strictures. Postoperative complications were not affected by the treatment of infundibula strictures (p=0.198).

CONCLUSIONS

Previous standard PCNL significantly impairs the outcomes of RIRS. Infundibula strictures can be found in 26.3% of the patients with residual stone fragments after standard PCNL for large burden kidney stones. The main site of infundibulum stricture after standard PCNL is the infundibulum of the entry calyx.

Novel Use of a Modified Triangular Prismatic Double-J Stent for 2- to 3-cm Renal Stones after One-Stage Retrograde Intrarenal Surgery

OBJECTIVES

To initially evaluate the outcomes of the modified triangular prismatic double-J (DJ) stent in the management of 2- to 3-cm renal stones after one-stage retrograde intrarenal surgery (RIRS).

METHODS

Patients with 2- to 3-cm renal stones who underwent one-stage RIRS with indwelling DJ stents were retrospectively evaluated. Eighty-eight patients who were placed the triangular prismatic DJ stents and 64 patients who received standard DJ stents were randomly included. The clinical characteristics and intraoperative and postoperative outcomes of the 2 groups were compared and analyzed.

RESULTS

The 2 groups had similar baseline characteristics. The urinary symptom score and pain score did not differ between groups (p > 0.05). The residual fragments of the 2 groups were similar 1 day after operation (p = 0.134). There was no significant difference in residual fragments in the lower calyx between groups at the time of stent removal (p = 0.834). The patients in the modified group had better spontaneous passage of residual fragments in the nonlower calyx than those in the standard group during the 2 weeks with the stents (p = 0.005). Fewer patients in the modified group had residual fragments (>4 mm) in the nonlower calyx (p = 0.026) and ureter (p = 0.010) than the patients with standard stents at the time of stent removal.

CONCLUSION

The indwelling triangular prismatic DJ stent is a safe and efficient treatment method. Patients with these stents had better spontaneous residual fragment passage than those with the standard DJ stents.

Residual Stone Fragments After Percutaneous Nephrolithotomy: Shockwave Lithotripsy vs Retrograde Intrarenal Surgery

Background: Despite technology incorporation to percutaneous nephrolithotomy (PCNL), residual stone fragments (RSFs) may still persist after PCNL and need to be addressed to avoid regrowth or ureteral obstruction. The objective of this study was to compare the outcomes of retrograde intrarenal surgery (RIRS) to extracorporeal shockwave lithotripsy (SWL) for treating patients with RSFs after a previous standard PCNL. Materials and Methods: Adult patients with RSF after a standard PCNL submitted to RIRS or SWL in our Institution from January 2017 to January 2020 were retrospectively studied. Stone-free rate (SFR) was evaluated on postoperative day (POD) 90 by noncontrast CT (NCCT) or ultrasound and kidney, ureter, and bladder radiograph (KUB) for each renal unit. Surgical complications based on Clavien-Dindo classification during the 90 days of follow-up were recorded. Sample size was calculated for a power of 80% and a significance level of 0.05, assuming SFR of 20% for SWL and 50% for RIRS. Results: Thirty-three patients treated by SWL were compared with 36 patients treated by RIRS. Hospitalization time was longer in the RIRS group (4.18 vs 12.33 hours, p = 0.001). SFR and success rate were lower in SWL than RIRS group (24.2% vs 58.3%, p = 0.007 and 30.3% vs 72.2%, p = 0.004, respectively), using POD 90 NCCT in 81.8% and ultrasound and KUB in 18.2% of the SWL group and using POD 90 NCCT in 100% of the RIRS group. Minor complications (Clavien-Dindo < III) occurred in 11 of 36 (30.6%) patients submitted to RIRS and in 2 of 33 (6.1%) patients submitted to SWL group (p = 0.025). Two patients (6.1%) of the SWL group had Clavien-Dindo IIIb complication owing to Steinstrasse and were submitted to ureteroscopy. Emergency room visits were similar between groups (6.1% vs 8.3%, p = 1.0). Conclusions: RIRS has better SFR, higher minor complications, and lower major complications than SWL for the treatment of RSFs after standard PCNL.

InsKid-a new mobile application (app) that measures the infundibulopelvic angle before retrograde intrarenal surgery more reliably than does other approaches: pilot study

OBJECTIVE

This study compared our program's ("InsKid") capability for measuring the infundibulopelvic angle (IPA) with existing ones.

METHODS

Prospectively, data from 50 patients with lower pole kidney stones with indications for retrograde intrarenal surgery (RIRS) were collected. All patients underwent computed tomography (CT)-urography. The IPA of each pelvicalyceal (PCS) unit was measured with the Elbahnasy's, Sampaio's, and "InsKid" methods. Results were compared. Finally, we compared the area under the receiver operating characteristic (ROC) curve (AUC) for predicting stone-free status after RIRS. We defined success as stone fragments ≤ 2 mm on the CT scan on the first postoperative day (POD1). The stone-free rate refers to no identifiable stone fragments on the POD1 CT. Test-retest reliability and face validity were defined to estimate psychometric properties of InsKid.

RESULTS

The success rate after first procedure was 87.5%. The average value of IPA using the Elbahnasy and Sampaio methods and our program were 85.2° ± 11.9°, 95.1° ± 10.1°, and 79.9° ± 13.0, respectively. There was a significant difference among the InsKid, Elbahnasy, and Sampaio (AUC = 0.762, 0.601, and 0.629, respectively) approaches with respect to the capability of predicting the immediate success of RIRS. Repeated measurement did not affect values of IPA (1.3° ± 0.7, p = 0.67). All specialist appreciated proposed software as highly useful (5/5).

CONCLUSION

This new application reproduces the intraoperative aspects of the PCS more clearly than the other methods and also provides an easy solution for clearly defining the IPA without relying on the central axes.

Consultation on kidney stones, Copenhagen 2019: aspects of intracorporeal lithotripsy in flexible ureterorenoscopy

Purpose

To summarize current knowledge on intracorporeal laser lithotripsy in flexible ureterorenoscopy (fURS), regarding basics of laser lithotripsy, technical aspects, stone clearance, lithotripsy strategies, laser technologies, endoscopes, and safety.

Methods

A scoping review approach was applied to search literature in PubMed, EMBASE, and Web of Science. Consensus was reached through discussions at the Consultation on Kidney Stones held in September 2019 in Copenhagen, Denmark.

Results and conclusions

Lasers are widely used for lithotripsy during fURS. The Holmium laser is still the predominant technology, and specific settings for dusting and fragmenting have evolved, which has expanded the role of fURS in stone management. Pulse modulation can increase stone ablation efficacy, possibly by minimizing stone retropulsion. Thulium fibre laser was recently introduced, and this technology may improve laser lithotripsy efficiency. Small fibres give better irrigation, accessibility, and efficiency. To achieve optimal results, laser settings should be adjusted for the individual stone. There is no consensus whether the fragmentation and basketing strategy is preferable to the dusting strategy for increasing stone-free rate. On the contrary, different stone scenarios call for different lithotripsy approaches. Furthermore, for large stone burdens, all laser settings and lithotripsy strategies must be applied to achieve optimal results. Technology for removing dust from the kidney should be in focus in future research and development. Safety concerns about fURS laser lithotripsy include high intrarenal pressures and temperatures, and measures to reduce both those aspects must be taken to avoid complications. Technology to control these parameters should be targeted in further studies.