Ultrasound guidance can be used safely for renal tract dilatation during percutaneous nephrolithotomy

Training ultrasound-guided percutaneous nephrostomy technique with porcine model

PURPOSE

There is increasing interest in the use of ultrasound for endoscopic and percutaneous procedures. Access can be achieved without radiation exposure under ultrasound guidance. Our aim was to develop a porcine-based training model for ultrasound-guided percutaneous renal access that could also be personalized to a specific patient.

MATERIALS AND METHODS

The Institutional Animal Care and Use Committee of Severance Hospital approved the study protocol. An anesthetized pig was placed in the dorsal lithotomy position. For the nephrostomy puncture, a Chiba biopsy needle with an echo tip was used under ultrasound guidance. Eight residents and three consultants in urology participated. Puncture time was defined as the nephrostomy time to confirm the flow of irrigation via the needle. After training, satisfaction survey results for clinical usability and procedural difficulty were evaluated.

RESULTS

The 5-point Likert scale satisfaction survey for clinical usability and procedural difficulty found mean results of 4.64 and 4.09 points, respectively. There were no differences between residents and consultants for either variable. For all participants combined, there was a significant difference for nephrostomy time between the first and second trials (278.8±70.6 s vs. 244.5±47.0 s; p=0.007). The between-trial difference was greater for residents (291.5±71.2 s vs. 259.1±41.9 s; p=0.039). The difference for the consultant was not significant (245.0±69.4 s vs. 205.7±42.5 s; p=0.250).

CONCLUSIONS

We developed a porcine-based ultrasound-guided nephrostomy puncture training model. Satisfaction survey results indicated high clinical usability and procedural difficulty. For nephrostomy time, the model was more effective for urology residents than for consultants.

Comparison of Treatment Outcomes for Fluoroscopic and Fluoroscopy-free Endourological Procedures: A Systematic Review on Behalf of the European Association of Urology Urolithiasis Guidelines Panel

CONTEXT

Endourological procedures frequently require fluoroscopic guidance, which results in harmful radiation exposure to patients and staff. One clinician-controlled method for decreasing exposure to ionising radiation in patients with urolithiasis is to avoid the use of intraoperative fluoroscopy during stone intervention procedures.

OBJECTIVE

To comparatively assess the benefits and risks of "fluoroscopy-free" and fluoroscopic endourological interventions in patients with urolithiasis.

EVIDENCE ACQUISITION

A systematic review of the literature from 1970 to 2022 was performed using the MEDLINE/PubMed, Embase, and Cochrane controlled trials databases and ClinicalTrials.gov. Primary outcomes assessed were complications and the stone-free rate (SFR). Studies reporting data on ureteroscopy and percutaneous nephrolithotomy (PCNL) were eligible for inclusion. Secondary outcomes were operative duration, hospital length of stay, conversion from a fluoroscopy-free to a fluoroscopic procedure, and requirement for an auxiliary procedure to achieve stone clearance.

EVIDENCE SYNTHESIS

In total, 24 studies (12 randomised and 12 observational) out of 834 abstracts screened were eligible for analysis. There were 4564 patients with urolithiasis in total, of whom 2309 underwent a fluoroscopy-free procedure and 2255 underwent a comparative fluoroscopic procedure for treatment of urolithiasis. Pooled analysis of all procedures revealed no significant difference between the groups in SFR (p = 0.84), operative duration (p = 0.11), or length of stay (p = 0.13). Complication rates were significantly higher in the fluoroscopy group (p = 0.009). The incidence of conversion from a fluoroscopy-free to a fluoroscopic procedure was 2.84%. Similar results were noted in subanalyses for ureteroscopy (n = 2647) and PCNL (n = 1917). When only randomised studies were analysed (n = 12), the overall complication rate was significantly in the fluoroscopy group (p < 0.001).

CONCLUSIONS

For carefully selected patients with urolithiasis, fluoroscopy-free and fluoroscopic endourological procedures have comparable stone-free and complication rates when performed by experienced urologists. In addition, the conversion rate from a fluoroscopy-free to a fluoroscopic endourological procedure is low at 2.84%. These findings are important for clinicians and patients, as the detrimental health effects of ionising radiation are negated with fluoroscopy-free procedures.

PATIENT SUMMARY

We compared treatments for kidney stones with and without the use of radiation. We found that kidney stone procedures without the use of radiation can be safely performed by experienced urologists in patients with normal kidney anatomy. These findings are important, as they indicate that the harmful effects of radiation can be avoided during kidney stone surgery.

2022 Recommendations of the AFU Lithiasis Committee: Percutaneous nephrolithotomy

Percutaneous nephrolithotomy (Labate et al.) is the standard procedure for the treatment of large (≥2cm) kidney stones. The patient can be in prone or modified supine position. The puncture is performed under fluoroscopy and/or ultrasound guidance. The stone-free rate seems to be comparable between miniaturized and standard PCNL. Procedures performed with smaller diameter instruments tend to be associated with significant lower blood loss, but longer procedure times. The limitation of the number of percutaneous tracts results in better preservation of the kidney function and lowers the risk of complications. The use of tranexamic acid during PCNL may be interesting for reducing the bleeding risk, the transfusion rate, and possibly the intervention duration. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis [EAU 2022]) and their adaptability to the French context.

Ultrasound-Only Percutaneous Nephrolithotomy Is Safe and Effective Compared to Fluoroscopy-Directed Percutaneous Nephrolithotomy

Introduction: Outcomes after ultrasound-only percutaneous nephrolithotomy (PCNL), in which no fluoroscopy is used, are not well known. The goal of this study was to compare outcomes of ultrasound-only and fluoroscopy-directed PCNL. Materials and Methods: Prospectively collected data from the Registry for Stones of the Kidney and Ureter database were reviewed for all patients who underwent PCNL at one academic center from 2015 to 2021. Primary outcomes were complications and stone-free rates (no residual fragments ≥3 mm). Results: Of the 141 patients who underwent ultrasound-only PCNL and 147 who underwent fluoroscopy-directed PCNL, there was no difference in complication rates (15% vs 16%, p = 0.87) or stone-free status (71% vs 65%, p = 0.72), respectively. After adjusting for body mass index, American Society of Anesthesiologists (ASA), stone size, and stone complexity by Guy score, ultrasound-only PCNL was not associated with any increased odds of complications (odds ratio [OR] 0.7, 95% confidence interval [CI] 0.3-1.6, p = 0.41) or residual stone fragments ≥3 mm (OR 1.0, 95% CI 0.5-1.9, p = 0.972) compared with fluoroscopy-directed PCNL. Ultrasound-only PCNL was associated with shorter operative time (median 99.5 vs 126 minutes, p < 0.001), and the use of ultrasound remained a significant predictor of short operative time (<100 minutes) after controlling for supine positioning, stone size, and stone complexity by Guy score (OR 2.31, 95% CI 1.01-5.29, p = 0.048). Patients in the ultrasound-only group were spared a mean radiation exposure dose of 10 mGy per procedure. Conclusions: Ultrasound-only PCNL is safe and achieves similar stone-free rates compared with fluoroscopy-directed PCNL with the added benefit of avoidance of radiation.

Ultrasound-Guided PCNL - Why Are We Still Performing Exclusively Fluoroscopic Access?

PURPOSE OF REVIEW

While urologists are traditionally taught to perform percutaneous nephrolithotomy (PCNL) utilizing exclusively fluoroscopy, ultrasound has emerged as a safe alternative. This article showcases the major reasons why ultrasound-guided access should be considered the first-line approach for performing access for PCNL.

RECENT FINDINGS

There continues to be a need to further reduce radiation exposure in the management of kidney stone patients. This review showcases how performing ultrasound-guided PCNL has been associated with a shorter learning curve, increased patient safety, and the ability to perform x-ray free PCNL. Ultrasound-guided PCNL is not only an achievable skill for urologists to learn but provides multiple advantages over traditional fluoroscopic access. As every effort should be given to help reduce radiation exposure for kidney stone patients as well as performing surgeons and operating theater personnel, endourologists should strive to add this technique to their armamentarium.

Ultrasound versus fluoroscopy as imaging guidance for percutaneous nephrolithotomy: A systematic review and meta-analysis

OBJECTIVES

To determine whether the outcomes of ultrasound-guided percutaneous nephrolithotomy (UG-PCNL), an alternative to traditional fluoroscopy-guided percutaneous nephrolithotomy (FG-PCNL), are comparable.

METHODS

A systematic search of PubMed, Embase, and the Cochrane Library was carried out to discover investigations comparing UG-PCNL to FG-PCNL, and accordingly, a meta-analysis of those studies was performed. The primary outcomes included the stone-free rate (SFR), overall complications based on Clavien-Dindo classification, duration of surgery, duration of patients' hospitalization, and hemoglobin (Hb) drop during the surgery. All statistical analyses and visualizations were implemented utilizing R software.

RESULTS

Nineteen studies, including eight randomized clinical trials (RCTs) and eleven observational cohorts, comprising 3016 patients (1521 UG-PCNL patients) and comparing UG-PCNL with FG-PCNL met the inclusion criteria of the current study. Considering SFR, overall complications, duration of surgery, duration of hospitalization, and Hb drop, our meta-analysis revealed no statistically significant difference between UG-PCNL and FG-PCNL patients, with p-values of 0.29, 0.47, 0.98, 0.28, and 0.42, respectively. Significant differences were discovered between UG-PCNL and FG-PCNL patients in terms of the length of time they were exposed to radiation (p-value< 0.0001). Moreover, FG-PCNL had shorter access time than UG-PCNL (p-value = 0.04).

CONCLUSION

UG-PCNL provides the advantage of requiring less radiation exposure while being just as efficient as FG-PCNL; thus, this study suggests prioritizing the use of UG-PCNL.

Best Practice in Interventional Management of Urolithiasis: An Update from the European Association of Urology Guidelines Panel for Urolithiasis 2022

PURPOSE

The European Association of Urology (EAU) has updated its guidelines on clinical best practice in urolithiasis for 2021. We therefore aimed to present a summary of best clinical practice in surgical intervention for patients with upper tract urolithiasis.

MATERIALS AND METHODS

The panel performed a comprehensive literature review of novel data up to May 2021. The guidelines were updated and a strength rating was given for each recommendation, graded using the modified Grading of Recommendations, Assessment, Development, and Evaluations methodology.

RESULTS

The choice of surgical intervention depends on stone characteristics, patient anatomy, comorbidities, and choice. For shockwave lithotripsy (SWL), the optimal shock frequency is 1.0-1.5 Hz. For ureteroscopy (URS), a postoperative stent is not needed in uncomplicated cases. Flexible URS is an alternative if percutaneous nephrolithotomy (PCNL) or SWL is contraindicated, even for stones >2 cm. For PCNL, prone and supine approaches are equally safe. For uncomplicated PCNL cases, a nephrostomy tube after PCNL is not necessary. Radiation exposure for endourological procedures should follow the as low as reasonably achievable principles.

CONCLUSIONS

This is a summary of the EAU urolithiasis guidelines on best clinical practice in interventional management of urolithiasis. The full guideline is available at https://uroweb.org/guidelines/urolithiasis.

PATIENT SUMMARY

The European Association of Urology has produced guidelines on the best management of kidney stones, which are summarised in this paper. Kidney stone disease is a common condition; computed tomography (CT) is increasingly used to diagnose it. The guidelines aim to decrease radiation exposure to patients by minimising the use of x-rays and CT scans. We detail specific advice around the common operations for kidney stones.

Ultrasound-guided renal access and balloon dilation for PCNL in the prone position: results of a multicenter prospective observational study

PURPOSE

To investigate the safety and efficacy of ultrasound-guided renal access and tract dilation using balloon dilators, as well as to identify suitable patients for this technique.

METHODS

Consecutive patients undergoing ultrasound-guided PCNL using balloon dilators between December 2019 and June 2020 in seven large medical centers from China were prospectively enrolled. Demographic and perioperative parameters of the patients were collected. Logistic regression analysis was used to analyze factors that would affect the success rate of tract establishment using ultrasound-guided renal access and balloon dilation.

RESULTS

A total of 170 patients were included in this study, among whom, 91.18% of the (155/170) patients had a successful tract establishment under ultrasound guidance on the first attempt. The stone-free rate was 83.5% and postoperative complications occurred in 14 patients (8.23%). In univariate analysis, history of ipsilateral surgery (p = 0.026), and stone diameter (p = 0.01) were significantly associated with tract establishment failure, while a larger width of the target calyx (p = 0.016) and the presence of hydronephrosis (p = 0.001) were significantly associated with a successful tract establishment. In multivariate analysis, only hydronephrosis in target calyx (p = 0.027) was a favorable factor for successful tract establishment, and the history of ipsilateral renal surgery (p = 0.012) was the only independent risk factor for failure of tract establishment.

CONCLUSION

It was safe and effective to establish percutaneous renal access with balloon dilation under whole-process ultrasound monitoring during PCNL. Furthermore, patients with a hydronephrotic target calyx and without history of ipsilateral renal surgery were most suited to this technique. Trial registration CHiCTR1800014448.

Presence of a Novel Anatomical Structure May Cause Bleeding When Using the Calyx Access in Mini-Percutaneous Nephrolithotomy

Background

Fused renal pyramid (FRP) is a kidney anatomical structure which was first identified by us. The vascular anatomy of FRP exhibits different from that of the normal renal pyramid (NRP), manifested by the distribution of the ectopic interlobar arteries in FRP. In this study, we analyzed the effect of FRPs on bleeding when using calyx access in mini-percutaneous nephrolithotomy (PCNL).

Patients and Methods

Overall, 633 patients who underwent ultrasound-guided single-tract mini-PCNL were divided into two groups according to the puncture method used: in group A, puncture was performed through the axial direction of the renal calyx, the line from the apex of the fornix to the center of the neck plane under B-mode ultrasound guidance; and in group B, Doppler ultrasound-guided axillary puncture through calyces corresponding to NRPs when the plane of renal column blood vessels on both sides was selected or calyx puncture through the hypovascular area of the FRPs. Relevant demographic and clinical data were retrospectively analyzed.

Results

The two groups exhibited similar baseline characteristics. No significant differences were found in hemoglobin reduction, puncture site, tract size, postoperative creatinine level, or stone-free rate between the two groups (P > 0.05). Blood transfusion and embolization rates in group B were significantly lower than those in group A (P = 0.03 and 0.045, respectively). No differences were found between the two groups in terms of persistent pain, hydrothorax, fever, subcapsular hematoma, and urosepsis (P > 0.05). The overall complication rate was not significantly different between the two groups (P = 0.505).

Conclusions

FRP is a non-negligible anatomical structure that may cause hemorrhage when using calyx access. Doppler ultrasound can identify ectopic blood vessels in FRPs to reduce bleeding during calyx access in mini-PCNL procedures.

A novel spherical-headed fascial dilator is feasible for second-stage ultrasound guided percutaneous nephrolithotomy: A pilot study

Objective

In second-stage percutaneous nephrolithotomy (PCNL), because the hydronephrosis has been decompressed, the dilated renal pelvis has resolved and the space is small. Consequently, introduction of the tip of the Amplatz dilator can cause injury to the opposite side of the renal-pelvic mucosa. In this study, we report the experimental and initial clinical performance of a spherical-headed fascial dilator developed specifically for second-stage PCNL.

Methods

The novel spherical-headed dilator was compared with existing tapered-headed dilators in configuration and in puncture resistance utilizing a static puncture test. Subsequently, a pilot clinical study was conducted during which patients scheduled to undergo second-stage PCNL from June 2019 to October 2019 in our center were enrolled. A typical ultrasound guided PCNL procedure was performed with the exception that the new spherical-headed fascial dilator was substituted for a tapered-headed one.

Results

Experimentally, stab resistance against polyethylene film was significantly increased using the novel spherical-headed dilator compared to the traditional tapered-headed dilators (p<0.005). In the clinical study, the novel dilators were successfully introduced into the renal pelvis and passed down the collecting system in all eight second-stage PCNL cases. There were no cases of renal pelvic perforation or brisk hemorrhage nor need for transfusion.

Conclusion

The design of the novel spherical-headed fascial dilator avoided the concentration of pressure at the tapered tip of the current Amplatz dilator by increasing the contact area and uniformly distributing and diffusing the pressure. Therefore, it is feasible to use the spherical-headed fascial dilator for second-stage PCNL.

Percutaneous nephrolithotomy - the puncture

OBJECTIVE

To determine what importance is given to the puncture and assistive technologies in percutaneous nephrolithotomy (PNL) in the current urological literature.

METHODS

PubMed was searched for English publications and reviews for the keywords: 'percutaneous nephrolithotomy', 'percutaneous nephrostomy', 'puncture'. The search was limited to the last 5 years, January 2016 until February 2021. Based on 183 abstracts, 121 publications were selected, read, and reviewed. References, older or seminal papers were read and cited if they contributed to a better understanding. A total of 198 references form the basis of this narrative review.

RESULTS

The puncture is frequently referred to as the most crucial part of PNL. In contrast, the influence of the puncture on the failure rate of PNL and the specific puncture-related complications seems to be low in the single-digit percentage range. However, there are no universally accepted definitions and standards measuring the quality of puncture. Consequently, the impact of the puncture on general PNL complications, on stone scores predicting success rates and on learning curves evaluating surgeons' performance have not been systematically studied. Assistive technologies rely on fluoroscopy and ultrasonography, the latter of which is becoming the preferred imaging modality for monitoring the entire procedure. Needle bending, a problem relevant to all puncture techniques, is not addressed in the urological literature.

CONCLUSIONS

The importance attached to puncture in PNL in the current urological literature is subjectively high but objectively low. Some basics of puncture are not well understood in urology. Disciplines other than urology are more actively involved in the development of puncture techniques.

Optically tracked needle for ultrasound guided percutaneous nephrolithotomy (PCNL) puncture: A preliminary report

Introduction Precise needle puncture of the renal collecting system is an essential step for successful percutaneous nephrolithotomy (PCNL). The use of ultrasound for puncture is receiving increased attention. Ultrasound has recognised limitations related to poor visualisation of the needle tip. We aimed to assess if an affordable open source computerized needle navigation training system, using optically tracked ultrasonography, could improve performance of simulated PCNL puncture by urological trainees, compared to conventional free hand manual sonographic puncture. Methods This study describes a PCNL navigation system which can be recreated with any standard ultrasound machine using relatively inexpensive components. The system allows the needle tip to be precisely appreciated in the ultrasound image, its trajectory planned, and the appreciation of needle tip to target calyx proximity aided by sound. Eight urology trainees participated in assessment of the PCNL training model. Alternating freehand (control) and tracked needle (experimental) punctures were performed on a phantom kidney. Total procedure and the number of reinsertions required were recorded. Results The mean time for freehand puncture was 89 seconds (range 13 - 173), while that of the optically tracked needle was 36 seconds (range 12 - 72). Thus, puncture time was significantly reduced by an average of 53 seconds (p=0.045) in the experimental arm. The mean number of needle reinsertions was 3,3 with freehand compared to 1,3 in the optically tracked puncture (p = 0.005). The mean square root error (MSRE) of the system was 1,8 mm. Conclusion This study demonstrates that affordable hardware and open source software can be used to construct an optically tracked ultrasound navigation system for PCNL training. Statistically significant reduced puncture time and number of passes required for successful puncture was demonstrated. We feel that computerised needle tracking during PCNL puncture deserves further evaluation in a training, and potentially, a clinical setting.

Trends of percutaneous nephrolithotomy in Saudi Arabia

Objective:

The objective of the study was to present the current practice patterns on percutaneous nephrolithotomy (PCNL) in Saudi Arabia and to compare it with the international patterns and to observe the adherence to the guidelines.

Materials and Methods:

A survey consisting of 28 questions was sent to urologists working in Saudi Arabia using a Google Forms questionnaire. The questioner covered most aspects of performing PCNL starting from preparing the patient till discharging him.

Results:

One hundred and thirty-two replied to the survey. Almost 70.2% performed PCNL and 59.1% of them learned PCNL during residency. The access was obtained by the urologists in 80.3% from the participants, 68.2% of them uses fluoroscopic guidance for the puncture. The majority (80.3%) perform PCNL in the prone position. Nearly 69.7% use the balloon dilators and 16.7% use the Amplatz dilators. For kidney drainage, 60.6% place a nephrostomy tube and a double-J stent (DJ stent) together and 4.5% perform tubeless PCNL (DJ stent only). About 45.5% stated that the introduction of flexible ureteroscopy decreased the rate of doing PCNL for >20%.

Conclusions:

Data obtained from a group of urologists in Saudi Arabia showed that the majority of urologists practicing in Saudi Arabia perform PCNL. They usually learn PCNL during residency. We observe that the majority of urologists attach to the original patterns in PCNL, i.e., they predominantly prefer the prone position and use fluoroscopy to gain the PCNL access. Furthermore, the data showed that new trends in PCNL did not gain a lot of momentum as few practices miniaturized PCNL and tubeless PCNL. The majority use balloon dilators and combined ultrasonic/pneumatic lithotripters. The complication rate encountered by the participants is concomitance with the published international figures. The introduction of flexible ureteroscopy highly decreased the rate of doing PCNL for most urologists.

European Association of Urology Section of Urolithiasis and International Alliance of Urolithiasis Joint Consensus on Percutaneous Nephrolithotomy

CONTEXT

Although percutaneous nephrolithotomy (PCNL) has been performed for decades and has gone through many refinements, there are still concerns regarding its more widespread utilization because of the long learning curve and the potential risk of severe complications. Many technical details are not included in the guidelines because of their nature and research protocol.

OBJECTIVE

To achieve an expert consensus viewpoint on PCNL indications, preoperative patient preparation, surgical strategy, management and prevention of severe complications, postoperative management, and follow-up.

EVIDENCE ACQUISITION

An international panel of experts from the Urolithiasis Section of the European Association of Urology, International Alliance of Urolithiasis, and other urology associations was enrolled, and a prospectively conducted study, incorporating literature review, discussion on research gaps (RGs), and questionnaires and following data analysis, was performed to reach a consensus on PCNL.

EVIDENCE SYNTHESIS

The expert panel consisted of 36 specialists in PCNL from 20 countries all around the world. A consensus on PCNL was developed. The expert panel was not as large as expected, and the discussion on RGs did not bring in more supportive evidence in the present consensus.

CONCLUSIONS

Adequate preoperative preparation, especially elimination of urinary tract infection prior to PCNL, accurate puncture with guidance of fluoroscopy and/or ultrasonography or a combination, keeping a low intrarenal pressure, and shortening of operation time during PCNL are important technical requirements to ensure safety and efficiency in PCNL.

PATIENT SUMMARY

Percutaneous nephrolithotomy (PCNL) has been a well-established procedure for the management of upper urinary tract stones. However, according to an expert panel consensus, core technical aspects, as well as the urologist's experience, are critical to the safety and effectiveness of PCNL.

Complications and surgical results of stone-directed antegrade pyelography compared to the retrograde pyelographic access method in percutaneous nephrolithotomy using ‘bull’s eye’ technique: A randomized clinical trial

Objectives:

This study aimed to evaluate the differences in outcomes and complications in stone-directed antegrade pyelography using the ‘bull’s eye’ technique in patients with renal stones versus the conventional method of percutaneous nephrolithotomy (PCNL). Although conventional PCNL access using retrograde pyelography is useful, it is time-consuming and may cause postoperative discomfort. Herein, we report our experience in the application of this new technique.

Methods:

Between January 2017 and June 2018, 100 patients participated in this randomized clinical trial. Stone-directed antegrade pyelography using the ‘bull’s eye’ technique under fluoroscopic guidance was used for percutaneous access in the intervention group. The second group, consisting of those who had undergone conventional PCNL using retrograde pyelography and ‘bull’s eye’ technique in the same period, were considered as the controls. Pre- and postoperative laboratory examinations, surgical results and complications were recorded and compared between the two groups.

Results:

A single calyceal puncture in partial staghorn and staghorn stone patients was sufficient in 72.2% of the antegrade group and in 78.9% of the retrograde group ( p=0.69). The double-puncture technique was necessary for 71.9% of renal pelvis stones in the antegrade group and for 9.4% in the retrograde group ( p<0.001). The antegrade approach reduced the mean operative time and analgesic requirement significantly ( p<0.001). No statistically significant difference, however, was found between the two groups regarding stone migration to the ureter, radiation time and postoperative complications.

Conclusions:

The stone-directed antegrade approach using the ‘bull’s eye’ technique is a safe and accurate method in PCNL access in patients with radiopaque and semi-opaque renal stones.

Minimizing radiation dose in management of stone disease: how to achieve 'ALARA'

PURPOSE OF REVIEW

Exposure to radiation is known to have adverse effects such as secondary malignancies. Patients with nephrolithiasis are exposed to radiation in the workup and treatment of their condition. Furthermore, exposure to radiation is often repeated due to the high recurrence rate of nephrolithiasis.

RECENT FINDINGS

We discuss practices inside and outside of the operating room to strive to keep radiation exposure as low as reasonably achievable (ALARA) for patients being treated for nephrolithiasis. These efforts include reduced dose computed tomography scans, fluoroless surgical techniques and new alternative technologies.

SUMMARY

Maintaining radiation exposure ALARA for our patients is increasingly practical. The urologist must make every effort to adhere to ALARA principles to protect patients from the stochastic effects of radiation.

Comparison of antegrade and retrograde ureterolithotripsy for proximal ureteral stones: a systematic review and meta-analysis

Background

Antegrade percutaneous ureterolithotripsy (URSL) could be a treatment option for large and/or impacted proximal ureteral stones, which are difficult to treat. To review the current approach and treatment outcomes and to compare the efficacy of retrograde and antegrade URSL for large proximal ureteral stones, we evaluated the unique perspectives of both surgical modalities.

Methods

This systematic literature review and meta-analysis was performed in July 2020. Articles on human studies and treatment of ureteral stones with URSL were extracted from the PubMed, MEDLINE, Embase, Cochrane Library, Scopus, and the Japan Medical Abstracts Society databases without any language restrictions. The risks of bias for randomized controlled trials (RCTs) and non-randomized controlled trials (non-RCTs) were assessed using the Cochrane risk of tool and the Risk of Bias in Non-randomized Studies- of Interventions tool, respectively.

Results

A total of 10 studies, including seven RCTs and three non-RCTs, were selected for the analysis; 433 and 420 cases underwent retrograde and antegrade URSL, respectively. The stone-free rate (SFR) was significantly higher in antegrade URSL than in retrograde URSL (SFR ratio: 1.17, 95% CI: 1.12-1.22; P<0.001), while the hospital stay was significantly longer in antegrade URSL than in retrograde URSL (standardized mean difference: 2.56, 95% CI: 0.67-4.46; P=0.008). There were no significant differences in the operation time and the overall complication rate between the two approaches.

Conclusions

Despite the heterogeneity of data and bias limitations, this latest evidence reflects real practice data, which may be useful for decision making.

Can ultrasound guidance reduce radiation exposure significantly in percutaneous nephrolithotomy in pediatric patients?

In this study, we aimed to compare clinical and technical outcomes between pediatric patients who underwent percutaneous nephrolithotomy (PCNL) under fluoroscopy (FL) and those that underwent this procedure under FL with ultrasound assistance (FLUSA). The data of 66 PCNL patients were analyzed retrospectively. Renal puncture was successful in 22 patients in the FLUSA group and 44 patients in the FL group. In all cases, FL was used for tract dilation and confirmation of ureteral catheter positioning at the beginning of the procedure. The sample consisted of 46 males and 20 females with a mean age of 7.2 ± 2.1 years (range 1-17 years). Stone size varied from 8.0 to 75.4 mm, and 89% of patients achieved a completely stone-free state. The median puncture time was 130.5 ± 25.3 s for FLUSA and 295 ± 82.8 s for FL, the median fluoroscopic screening time was 95 ± 33 and 230 ± 116 s, respectively, and the median radiation dose was 19.04 ± 9.9 dGy/cm² and 54 ± 21.4 dGy/cm², respectively. The median puncture time, fluoroscopic screening time, and radiation dose were statistically lower in the FLUSA group (p = 0.001, Mann-Whitney U test). The greatest problem in PCNL is the use of fluoroscopy. Due to some anatomical differences from adults, applying PCNL in pediatric patients using only ultrasound may decrease the success rate. Puncture with ultrasound significantly reduces the radiation dose in children. Puncture with ultrasound and dilation under fluoroscopy is a successful and safe treatment method with low morbidity and high success rates and shorter hospital stay in pediatric patients.

Efficacy and safety of modified tract dilation technique using simultaneous pulling of proximal and distal ends of a guidewire for percutaneous nephrolithotomy in modified supine position

Purpose

Recently, the needs for supine percutaneous nephrolithotomy (PCNL) have become more increased because of an easy approach for endoscopic combined intrarenal surgery. However, making a nephrostomy tract during supine PCNL is more difficult than prone position due to movable kidney. To overcome this limitation, we used a modified nephrostomy tract dilation (MTD) technique using guidewire traction.

Materials and Methods

From January 2014 to June 2019, a total of 259 patients underwent PCNL in the modified supine position. Among them, the MTD technique was performed in 171 patients. For the MTD technique, two hydrophilic guidewires were passed from the nephrostomy tract and brought out through the urethra, then both proximal and distal ends were contralaterally pulled with tension for the easy placement of a fascia-cutting needle and a balloon catheter. We analyzed the efficacy of this technique in comparison with the conventional method.

Results

Intraoperative radiation exposure time (RET) (68.87 vs. 212.11 s) and hospital stay (5.90 vs. 6.74 days) were significantly shorter, while the success rate (77.2% vs. 63.6%) was significantly higher in the MTD group. Multivariate analysis showed that only the maximal stone diameter (odds ratio [OR], 1.928; 95% confidence interval [CI], 1.314–2.828; p=0.001) and MTD technique (OR, 0.017; 95% CI, 0.007–0.040; p<0.001) were independent factors for predicting short RET (<120 s).

Conclusions

This study demonstrated that MTD technique can be effectively and safely performed in modified supine position PCNL, and it can be helpful in reducing RET and enhancing success rates.

Personalized Renal Collecting System Mockup for Procedural Training Under Ultrasound Guidance

Objective: In recent years, there has been increasing interest in the use of ultrasound guidance for endoscopic and percutaneous procedures. Kidney mockups could be used for training, however, available mockups are normally incompatible with ultrasound imaging. We developed a reproducible method to manufacture an ultrasound-compatible collecting system mockup that can be made at urology laboratories. Methods: Positive and negative molding methods were used. A three-dimensional (3D) digital model of a urinary collecting system and the overlying skin surface were segmented from computed tomography. A containment mold (negative) was made following the shape of the skin surface using 3D printing. A collecting system mold (positive) was also 3D printed, but made of a dissolvable material. The containment mold was filled with a gelatin formula with the collecting system mold submersed in situ within. After the gelatin solidified, a solution was used to dissolve the collecting system mold, but not the gelatin, leaving a cavity with the shape of the collecting system. The gelatin was extracted from the container mockup and the collecting system cavity was filled with water. The mockup was imaged with ultrasound to assess echogenicity and suitability for simulating ultrasound-guided procedures. Results: A clear shape corresponding to the collecting system was observed inside the gel structure. Structural integrity was maintained with no observable manufacturing marks or separation seams. Ultrasound images of the mockup demonstrated clear differentiation at the gelatin/water interface. A mock stone was placed in the collecting system and needle targeted to simulate percutaneous needle access. Conclusion: We developed a simple method to manufacture a personalized mockup of the renal collecting system of a patient that can be used for ultrasound-guided percutaneous needle access. Generic collecting system mockups can be used for training, and patient-specific models can be used to simulate and decide the best access path before a clinical case.