Clinical significance of residual fragments in 2015: impact, detection, and how to avoid them

Clinical study of UMP and RIRS in 1.0-2.0 cm diameter renal/upper ureteral calculi

BACKGROUND

The purpose of this study was to compare the efficacy and safety of Ultra-mini-percutaneous nephrolithotomy (UMP) and Retrograde intrarenal surgery (RIRS) for renal/upper ureteral calculi in 1.0-2.0 cm diameter.

METHODS

From October 2017 to October 2022, the surgical treatment of patients with renal/upper ureteral calculi in 1.0-2.0 cm diameter who were admitted to our hospital was retrospectively analyzed. They were divided into two groups, the UMP group (sixty-two cases) and the RIRS group (one hundred and nine cases), according to the different surgical methods. Baseline data includes general information, stone size, location, CT value, hydronephrosis, creatinine level, etc. RESULTS: Intraoperative blood loss was 33.6 ± 8.5 ml in the UMP group was significantly more than 4.3 ± 0.7 ml in the RIRS group (P < 0.05). Intraoperative renal pelvis pressure of UMP group 10.5 ± 1.3 mmHg was significantly lower than RIRS group 23.6 ± 5.6 mmHg (P < 0.05). The incidence of postoperative infection was higher in the RIRS group (thirteen cases [11.93%]), and one case ([1.61%]) in the UMP group (P < 0.05). Routine CT scans on the second day and two months after surgery showed that the stone clearance rates in the UMP group were 87.1% and 93.5%, respectively, higher than those in the RIRS group (69.7% and 79.8%, respectively; P < 0.05).

CONCLUSION

UMP has the advantage of a higher stone-free rate but a higher risk of injury and bleeding. The advantages of RIRS include less trauma, less bleeding, and faster recovery, but lower stone-free rates and a higher risk of infection.

The significance of clinically insignificant residual fragments after percutaneous nephrolithotomy: an analysis into the relevance of complete stone clearance

PURPOSE

After treatment for kidney stones, residual fragments with a diameter of ≤ 4 mm are traditionally referred to as 'clinically insignificant residual fragments'. We hypothesize that patients with these fragments are at an increased risk for stone-related morbidity, such as complaints, hydronephrosis, and stone regrowth, when compared to stone-free patients. This study aimed to investigate the relevance of complete stone clearance in surgical treatment of urolithiasis.

METHODS

We conducted a single-center retrospective cohort study. Patients who underwent percutaneous nephrolithotomy between 2015 and 2020 were included if a CT-scan was available within 6 months after the procedure, and the follow-up duration was at least 1 year. The stone-free status at the end of the first stone episode during the study period was categorized as fully stone-free, not stone-free with small residual fragments (≤ 4 mm) and not stone-free with large residual fragments (> 4 mm). Follow-up data were collected, including stone-related events and re-intervention rates.

RESULTS

A total of 103 subjects were included with a median follow-up of 21.4 months. Stone-related events occurred in 10 (29.4%) of the fully stone-free subjects, 20 (58.8%) of the subjects with small residual fragments and 25 (71.4%) of the subjects with large residual fragments. The stone-related event-free survival per subgroup resulted in a significantly different survival distribution in a log rank test (p = 0.008).

CONCLUSION

A complete stone-free status seems to be of fundamental importance for decreasing stone-related morbidity. Further developments and research should focus on optimizing the full clearance of stone material during PCNL.

Efficacy and safety of fluoroless ureteroscopy and retrograde intrarenal surgery for the treatment of urolithiasis: A comparative study

INTRODUCTION

Ureteroscopy (URS) and retrograde intrarenal surgery (RIRS) are traditionally guided by fluoroscopy, but the risks of exposure to ionizing radiation may present a matter of concern for patients and urologists. The aim of this study was to evaluate the efficacy and safety of fluoroless URS and RIRS compared with conventional fluoroscopy-guided procedures for the treatment of ureteral and renal stones.

MATERIAL AND METHODS

Patients treated with URS or RIRS for urolithiasis between August 2018 and December 2019 were retrospectively evaluated and grouped according to the use of fluoroscopy. Data was collected from individual patient records. The main outcomes were stone-free rate (SFR) and complications, compared between the fluoroscopy and fluoroless groups. A subgroup analysis by type of procedure (URS and RIRS) and a multivariate analysis to identify predictors of residual stones were conducted.

RESULTS

A total of 231 patients met the inclusion criteria: 120 (51.9%) in the conventional fluoroscopy group and 111 (48.1%) in the fluoroless group. No significant differences were found between groups regarding SFR (82.5% vs 90.1%, p=.127) or postoperative complication rate (35.0% vs 31.5%, p=.675). In the subgroup analysis these variables did not present significant differences, regardless of the procedure considered. In the multivariate analysis the fluoroless technique was not an independent predictor of residual lithiasis (OR 0.991; 95% IC 0.407-2.411; p=.983), when adjusted for procedure type, stone size and stone number.

CONCLUSION

URS and RIRS can be done without fluoroscopic guidance in selected cases, without affecting the efficacy or safety of the procedure.

High-frequency shock wave lithotripsy: stone comminution and evaluation of renal parenchyma injury in a porcine ex-vivo model

BACKGROUND

The electrohydraulic high-frequency shock wave (Storz Medical, Taegerwilen, Switzerland) is a new way to create small fragments with frequencies up to 100 Hertz (Hz). This study evaluated the efficacy and safety of this method in a stone and porcine model.

MATERIALS AND METHODS

BEGO stones were put in a condom in a specifically designed fixture treated with different modulations to see stone comminution. Standardized ex vivo porcine model with perfused kidneys with 26 upper and lower poles of 15 kidneys was treated with the following modulations: voltage 16-24 kV, capacitor 12 nF and frequency up to 100 Hz. 2000-20,000 shock waves were applied to each pole. The kidneys were perfused with barium sulfate solution (BaSO4) and x-ray was performed to quantify the lesions using pixel volumetry.

RESULTS

There was no correlation between the number of shock waves and the powdering degree or the applied Energy and the grade of pulverization in the stone model. Regarding the perfused kidney model, the number of shock waves, applied voltage and frequency had no direct correlation with the occurrence of parenchymal lesions The detected lesions of the renal parenchyma were minimal, technical parameters had no significant impact and the lesions did not differ from the results of former experiments using 1-1.5 Hz in the same model.

CONCLUSIONS

High-frequency shock wave lithotripsy can produce small stone fragments to pass in a very short time. The injury to the renal parenchyma is comparable to the results of the conventional SWL using 1-1.5 Hz.

Novel flexible vacuum-assisted ureteral access sheath(FV-UAS) can actively control intrarenal pressure and obtain a complete stone-free status

OBJECTIVES

To compare the safety and effectiveness of a novel flexible vacuum-assisted ureteral access sheath (FV-UAS) and traditional ureteral access sheath (UAS) in simulating retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

Amanometric model was established in porcine kidneys to observe the change inintrarenal pressure in the FV-UAS and traditional UAS groups at different irrigation fluid velocities of 30 ml/min, 50 ml/min, 80 ml/min, and 100 ml/min. Establish a kidney stone model (with 0.2 g, dry, ≤ 5 mm stones) to simulate RIRS. A total of 20 porcine kidneys wererandomly numbered from 1 to 20 (FV-UAS group, 1-10; traditional UAS group, 11-20). The stone volume clearance rate and operation time were compared between the two groups. [" Stone volume clearance rate= (1-(residual stone volume)/(preoperative stone volume))×100%" )]. Stones volume was obtained by computed tomography (CT) preoperatively and postoperatively.

RESULTS

FV-UAS can follow flexible ureteroscopy (f-URS) to cross the ureteropelvic junction (UPJ) and into the renal pelvis and calyces. FV-UAS can actively make intrarenal pressure (IRP) less than 10 cmH2O by adjusting the negative values atdifferent irrigation fluid velocities. The mean residual stone volume of the FV-UAS vs. traditional UAS groups was33.7 mm3 vs. 92.5 mm3 (P = 0.017). The mean stone volume clearance rates of the FV-UAS vs. traditional UAS groups were 98.5 % and95.9 %, respectively (P = 0.017). Seven cases achieved complete stone-free status in the FV-UAS group. All patients hadresidual fragments postoperatively in the traditional UAS group.

CONCLUSIONS

FV-UAS can follow f-URS to cross the UPJ and into the renal pelvis and calyces, avoiding the interference of UPJ in controlling IRP. FV-UAS can actively control the IRP to be reduced to the desired range by adjusting the negative value under any irrigation fluid velocity. FV-UAS close to the stone can achieve complete stone-free in RIRS.

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.

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

The removal of kidney stones can lead to small residual fragments remaining in the human body. Residual stone fragments can act as seeds for kidney stone crystallization and may necessitate another intervention. Therefore, it is important to create a consistent model with a particle size comparable to the range of kidney stone fragments. Thus, the size-determining parameters such as supersaturation ratio, energy input, and pH value are examined. The batch crystallizations were performed with supersaturation ratios between 5.07 and 6.12. The compositions of the dried samples were analyzed with Raman spectroscopy, infrared spectroscopy, and X-ray diffraction (XRD). The samples were identified as calcium oxalate monohydrate with spectroscopic analysis, while calcium oxalate dihydrate being the most prominent crystalline species at all supersaturation ratios for the investigated conditions. The aggregate size, obtained with analytical centrifugation, varied between 2.9 and 4.3 μm, while the crystallite domain size, obtained from XRD, varied from 40 to 61 nm. Our results indicate that particle sizes increase with increasing supersaturation, energy input, and pH. All syntheses yield a high particle heterogeneity and represent an ideal basis for reference materials of small kidney stone fragments. These results will help better understand and control the crystallization of calcium oxalate and the aggregation of such pseudopolymorphs.

In-vitro comparison of two electromagnetic shock-wave generators: low-pressure-wide focus versus high-pressure small focus - the impact on initial stone fragmentation and final stone comminution

CONTEXT

Recently developed concepts for higher efficacy ESWL with low-pressure wide focus systems resulting in finer fragmentation of the calculi.

OBJECTIVE

To compare two different electromagnetic shock wave sources (low-pressure wide focus (XL) versus high-pressure small focus (SL)) by sound-field measurements and in-vitro fragmentation.

EVIDENCE ACQUISITION

The CS-2012A XX-ES lithotripter (self-focusing electromagnetic shock-wave generator with concave spherical curved electrical coil; Xinin Lithotripter = XL) was compared to the Siemens Lithoskop (= SL) (electromagnetic generator with a flat electric coil with an acoustical lens). Different sound-field measurements were performed using a fiber-optic hydrophone. Measurements at three different power settings (XL: 8.0kV, 9.3kV and 10.3kV; SL: Level 1, 5 and 8). 10 ATS-stones and 15 BegoStones (9.3 kV, Level 3) with a frequency of 90/minute (SL) and 20/minute (XL). Number of impulses to the first crack and for complete stone comminution (residual fragments <2mm) were documented.

RESULTS

The median number of shock waves for the first crack in ATS-stones with the XL was 12 (10-14), with the SL 7 (6-9). Complete disintegration was accomplished after 815 (782-824) shock waves with XL, 702 (688-712) with SL. The difference was not statistically significant. The median number of shock waves to produce the first crack in BegoStones was 524 (504-542) with XL and only 151 (137-161) with SL. Numbers of shock waves for complete disintegration did not differ significantly (XL:2518 vs SL:2287). Using a wide focus with low pressure shows more homogeneous disintegration.

CONCLUSION

Two stone models showed significant differences regarding form and time of the initial fragmentation. Impulses for stone comminution did not differ significantly. The advantages of a low-pressure wide focus-system include minimal trauma and a homogeneous fragment size but is more time consuming. High-pressure small focus systems are clinically effective.

Novel Biocompatible Adhesive to Remove Stone Dust: Usability Trial in a Kidney Model

Introduction and Objective: "Clinically insignificant residual fragments" are an independent predictive factor for recurrence of nephrolithiasis. To improve the stone-free rates (SFR), we tested the viability of a novel bioadhesive system for intrarenal embedding and retrieval of residual fragments <1 mm in a kidney model. Materials and Methods: All procedures were performed in a standardized setting, including a kidney model (Kidney module right, Samed GmbH, Dresden) in a plastic basin filled with water. We used a Viper URF flexible ureterorenoscope (fURS) (6.6/8F, Richard Wolf, Knittlingen). A mean amount of 138 mg (standard deviation [SD] ±32.2 mg) of sand grains (range, 0.2-0.8 mm) was inserted in renal calices of the kidney model. We assessed the extraction efficacy of fURS using the bioadhesive system. In total, eight different surgeons performed each one trial, respectively. The endoscopic and macroscopic SFR, the level of the surgeons' experience, and the overall time of stone retrieval were evaluated. Additionally, a survey of the participants was conducted, to assess the contentment with this novel system. Results: The extraction of the sand grains was only possible using the bioadhesive system, otherwise they were too small sized to grab with a retrieval basket. The total SFR was 84% (SD ±11.7%). The operation time (p = 0.052) and the percentage of extracted sand grains (p = 0.194) were not significantly different between experienced and less experienced surgeons. All participants stated that it was a promising technique, which they could imagine using on a daily basis. Conclusions: The bioadhesive system improves the SFR with fragments from 0.2 to 0.8 mm (0% vs 84%). Also, the performance of this operation is not dependent on the surgeon's experience level. This method might improve the SFR in difficult anatomic conditions, that is, lower calices or anomalous kidneys.

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.

[Innovative laser technologies in the treatment of urolithiasis : A change to more gentle methods with increased patient safety]

Management of urolithiasis has undergone fundamental changes with the introduction of extracorporeal shock wave lithotripsy (ESWL) and percutaneous and ureterorenoscopic techniques in the 1980s. Since then, these minimally invasive techniques have been continuously optimized and specific laser techniques for stone disintegration have emerged. Besides the established holmium laser, other types of lasers are also emerging. Especially the thulium fiber laser is the subject of promising research due to its variable adjustment options. In terms of patient safety, both holmium and thulium techniques seem to be similar . While serious direct physical lesions are rare, there is increasing evidence of clinically relevant secondary thermal injury due to increased temperatures in the upper urinary tract during treatment. Our research group has recently demonstrated in both in vitro and in vivo (porcine animal model) experiments that monitoring the fluorescence spectra of calculi allows precise target differentiation between stone, tissue, and endoscope components. Consequently, pulse emissions were only emitted when stone material was detected. We believe that target monitoring will minimize the risk of laser-induced urothelial damage and decrease energy release into the upper urinary tract allowing adequate temperature management.

Extracorporeal shock-wave lithotripsy: is it still valid in the era of robotic endourology? Can it be more efficient?

PURPOSE OF REVIEW

The aim of the article is to evaluate the actual role of extracorporeal shock-wave lithotripsy (ESWL) in the management of urolithiasis based on the new developments of flexible ureterorenoscopy (FURS) and percutaneous nephrolithotomy (PCNL).

RECENT FINDINGS

In Western Europe, there is a significant change of techniques used for treatment of renal stones with an increase of FURS and a decrease of ESWL. The reasons for this include the change of indications, technical improvement of the endourologic armamentarium, including robotic assistance. Mostly relevant is the introduction of digital reusable and single-use flexible ureterorenoscopes, whereas micro-PCNL has been abandoned. Some companies have stopped production of lithotripters and novel ideas to improve the efficacy of shock waves have not been implemented in the actual systems. Promising shock-wave technologies include the use of burst-shock-wave lithotripsy (SWL) or high-frequent ESWL. The main advantage would be the very fast pulverization of the stone as shown in in-vitro models.

SUMMARY

The role of ESWL in the management of urolithiasis is decreasing, whereas FURS is constantly progressing. Quality and safety of intracorporeal shock-wave lithotripsy using holmium:YAG-laser under endoscopic control clearly outweighs the advantages of noninvasive ESWL. To regain ground, new technologies like burst-SWL or high-frequent ESWL have to be implemented in new systems.

Computed tomography window affects kidney stones measurements

OBJECTIVES

Measurements of stone features may vary according to the non-contrast computed tomography (NCCT) technique. Using magnified bone window is the most accurate method to measure urinary stones. Possible differences between stone measurements in different NCCT windows have not been evaluated in stones located in the kidney. The aim of this study is to compare measurements of kidney stone features between NCCT bone and soft tissue windows in patients submitted to retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

Preoperative and 90th postoperative day NCCT were performed in 92 consecutive symptomatic adult patients (115 renal units) with kidney stones between 5 mm to 20 mm (< 15 mm in the lower calyx) treated by RIRS. NCCT were evaluated in the magnified bone window and soft tissue window in three axes in a different time by a single radiologist blinded for the measurements of the NCCT other method.

RESULTS

Stone largest size (7.92±3.81 vs. 9.13±4.08; mm), volume (435.5±472.7 vs. 683.1±665.0; mm3) and density (989.4±330.2 vs. 893.0±324.6; HU) differed between bone and soft-tissue windows, respectively (p<0.0001) 5.2% of the renal units (6/115) were reclassified from residual fragments > 2 mm on soft tissue window to 0-2 mm on bone window.

CONCLUSION

Kidney stone measurements vary according to NCCT window. Measurements in soft tissue window NCCT of stone diameter and volume are larger and stone density is lesser than in bone window. These differences may have impact on clinical decisions.

Viability and biocompatibility of an adhesive system for intrarenal embedding and endoscopic removal of small residual fragments in minimally-invasive stone treatment in an in vivo pig model

PURPOSE

To evaluate the viability and biocompatibility of a novel, patented bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy. Complete stone clearance via active removal of residual fragments (RF) after intracorporeal laser lithotripsy may be time-consuming and fail in many cases. Therefore, the novel adhesive has been developed and evaluated for the first time in an in vivo pig model in the present work.

METHODS

Four female domestic pigs underwent flexible ureteroscopy (RIRS) or percutaneous nephrolithotomy (PNL) under general anesthesia (8 kidneys, 4 × RIRS, 4 × PNL) evaluating the bioadhesive system.

INTERVENTIONS

RIRS without adhesive system (sham procedure, kidney I); 3 × RIRS using the bioadhesive system (kidneys II-IV); and 4 × PNL using the bioadhesive system (V-VIII). We endoscopically inserted standardized human stone probes followed by comminution using Ho:YAG lithotripsy. The bioadhesive (kidney II-VIII) was then applied and the adhesive-stone fragment complex extracted. After nephrectomy, all kidneys were evaluated by two independent, blinded pathologists. Endpoints were the procedure's safety and adhesive system's biocompatibility.

RESULTS

We observed no substantial toxic effects. We were able to embed and remove 80-90% of fragments. However, because of the pig's hampering pyelocaliceal anatomy, a quantified, proportional assessment of the embedded fragments was compromised.

CONCLUSIONS

For the first time, we demonstrated the proven feasibility and safety of this novel bioadhesive system for embedding and endoscopically removing small RF in conjunction with a lack of organ toxicity in vivo.

New for Old-Coagulum Lithotomy vs a Novel Bioadhesive for Complete Removal of Stone Fragments in a Comparative Study in an Ex Vivo Porcine Model

OBJECTIVES

To evaluate a recently reported new bioadhesive system for the retrieval of small residual fragments (RFs) after intracorporeal lithotripsy, we systematically compared this system with coagulum lithotomy in retrograde intrarenal surgery.

MATERIALS AND METHODS

We extracted 30 human stone fragments (≤1 mm) in an ex vivo porcine kidney model using a flexible ureteroscope for three groups: (1) the novel bioadhesive, (2) autologous blood as a natural adhesive, and (3) (control group) a conventional retrieval basket. Each group consisted of 15 test runs. Outcomes were evaluated regarding the macroscopic stone-free rate (SFR), retrieval time, and number of ureteral passages.

RESULTS

For groups 1 and 2, a significant advantage in stone clearance, mean retrieval time, and number of retrievals was detected compared to the control group (p = 0.001). The time and number of retrievals were significantly lower in group 1 (10:36 minutes, p = 0.001) than in group 2 (26:12 minutes, p = 0.001), with shorter clotting time and better visibility.

CONCLUSIONS

These data show the general feasibility of intrarenal RF embedding to improve the SFR. Our data furthermore suggest the superiority of the artificial bioadhesive embedding agent over the application of native blood. Further in vivo studies and other research are necessary to confirm the adhesive's effect in patients.

What is the fate of insignificant residual fragment following percutaneous nephrolithotomy in pediatric patients with anomalous kidney? A comparison with normal kidney

Pediatric population has increasing incidence of renal calculus and it is estimated to be around 50/10,000 population. The treatment of choice for large and complex stone in anomalous kidney is percutaneous nephrolithotomy (PCNL). The fate of insignificant residual fragment after PCNL in pediatric patients is not well documented. Here, we are reporting our long-term experience and follow-up of insignificant residual fragment in pediatric patients with anomalous kidney in comparison to normal kidney. Intuitional ethical approval was taken. A retrospective analysis of PCNL in pediatric (<18 years) anomalous kidney was performed from 2001 to 2013. The data of 52 pediatric patients with anomalous kidney (group B) have been compared to 251 normal kidneys (group A). The mean age of the patients was 7.83 + 3.45 (range 3-18) in group A and 8.21 ± 3.25 (range 5-18) in group B. The mean size of the insignificant residual fragment was 2.2 + 0.5 mm (1-4) in group A and 2.1 + 0.6 mm (range 1-4) in group B. Most of these residual fragments were single in number (72.55 vs. 67.30%, respectively). 54.98% children in group A and 67.30% in group B were symptomatic in the follow-up. Stone size was increased, stable and spontaneously passed in 49.8 vs. 71.15, 22.7 vs. 19.23 and 27.49 vs. 9.61% (p < 0.03), respectively, over mean follow-up of 50.34 months. Insignificant residual fragments in children are notorious for regrowth (49.8% in normal and 71.15% in anomalous kidney) in future. Most of the children will require symptomatic treatment (55.37 vs. 82.69%) or reintervention (39 vs. 46%) for insignificant residual fragment.

[Stone treatment tomorrow and the day after]

Urological and surgical treatment of urinary stones are highly technological and technology-driven disciplines in present-day surgery. German medical engineering has always been recognized for its technical innovations in endoscopic surgery. Current and future trends are indicative of further miniaturization and automation of surgical instruments and assist systems to facilitate endourological procedures as well as improvements in the quality of results and ergonomics. These technologies include, e. g. 3D-tracking to facilitate access to the pelvicaliceal system for percutaneous nephrolithotomy (PNL) or robotic master-slave systems for endourology. The aim of all future stone treatment should be complete stone removal. This could be achieved by improved stone fragmentation ("micron-sized debris") or complete removal of fragments (e. g. using a "stone glue"). Integration of diagnostic procedures and treatments will constitute a key aspect of future developments in medical engineering. Intelligent laser systems may be capable of distinguishing stones from mucosa and artificial surfaces and may be used for immediate stone analysis during surgery. A simpler and faster availability of metabolic ("metabolomics") and genetic ("genomics") diagnostics will help to facilitate and improve individual metaphylaxis, e. g. in patient self-management. Nanotechnology and microrobots that may be used for endoluminal diagnostics and treatment of the urinary tract are already in development.

Novel Biocompatible Adhesive for Intrarenal Embedding and Endoscopic Removal of Small Residual Fragments after Minimally Invasive Stone Treatment in an Ex Vivo Porcine Kidney Model: Initial Evaluation of a Prototype

PURPOSE

Residual fragments related to endoscopic intracorporeal lithotripsy are a challenging problem. The impact of residual fragments remains a subject of discussion and growing evidence highlights that they have a central role in recurrent stone formation. Therefore, we developed a novel bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy in an ex vivo porcine kidney model.

MATERIALS AND METHODS

In a standardized setting 30 human stone fragments 1 mm or less were inserted in the lower pole of an ex vivo porcine kidney model. We assessed the extraction efficacy of flexible ureteroscopy using the bioadhesive system in 15 preparations and a conventional retrieval basket in 15. Outcomes were compared regarding the endoscopic and macroscopic stone-free rate, and overall time of retrieval.

RESULTS

Embedding and retrieving the residual fragment-bioadhesive complex were feasible in all trial runs. We observed no adverse effects such as adhesions between the adhesive and the renal collecting system or the instruments used. The stone-free rate was 100% and 60% in the bioadhesive and conventional retrieval groups, respectively (p = 0.017). Mean retrieval time was significantly shorter at 10 minutes 33 seconds vs 36 minutes 56 seconds in the bioadhesive group vs the conventional group (p = 0.001).

CONCLUSIONS

This novel method involving adhesive based complete removal of residual fragments from the collecting system has proved to be feasible. Our evaluation in a porcine kidney model revealed that this technology performed well. Further tests, including inpatient studies, are required to thoroughly evaluate the benefit and potential drawbacks of bioadhesive based extraction of residual fragments after intracorporeal lithotripsy.

Endoscopically Determined Stone Clearance Predicts Disease Recurrence Within 5 Years After Retrograde Intrarenal Surgery

OBJECTIVE

To assess stone-related events (SREs) requiring retreatment in a series of 100 consecutive patients treated by retrograde intrarenal surgery (RIRS) for renal stones and to evaluate potential risk factors thereof.

PATIENTS AND METHODS

The primary outcome was incidence of SRE (medical or surgical treatment). Secondary outcomes included side of SRE, time to SRE, and late complications. Analysis of potential risk factors included high-risk stone formers (HRSFs), obesity, high stone burden, and lower pole stones. In addition, we evaluated endoscopically determined small residual fragments (SRF) of <1 mm (i.e., fragments too small for retrieval) as an independent risk factor.

RESULTS

Eighty-five of the 99 patients were followed up for a mean of 59 months (31-69), among whom 26 (30.1%) had SRE. Thirty-four of the 85 (40%) patients were HRSFs, 22 of whom experienced SRE (both sides) during follow-up (64.7%, p < 0.001). Eight of the 17 patients (47.1%) with SRF experienced ipsilateral side SRE compared with 13 (19.1%) of the 68 without SRF (p = 0.022, hazard ratio 2.823, 95% confidence interval [95% CI] 1.16, 6.85). Risk for ipsilateral SRE was unaffected by the presence of SRF among HRSFs (p = 0.561). Of low-risk patients with SRF, 33.3% experienced ipsilateral SRE, while those without SRF experienced no ipsilateral SRE (p < 0.001).

CONCLUSION

Endoscopically determined stone clearance predicts disease recurrence within 5 years after RIRS. Even SRF are an important risk factor for future stone-related (ipsilateral) events; therefore, patients with residual fragments of any size should not be labeled "stone free" and endoscopic stone treatment should aim at complete stone clearance.