The learning curve for access creation in solo ultrasonography-guided percutaneous nephrolithotomy and the associated skills

Analyzing learning curve for supine percutaneous nephrolithotomy in urology resident training programme: comparative analysis

INTRODUCTION

This article attempts to provide a comprehensive review of the learning objectives and importance of the supine percutaneous nephrolithotomy (PCNL) technique.

MATERIAL METHOD

We retrospectively reviewed the cases of Supine PCNL between January 2018 and January 2024. We divided the groups into 3: residents between 2 and 3 years (Group 1), residents between 4 and 5 years (Group 2), and endourologist (Group 3). The 2-3-year resident started to perform PCNL for the first time, while the 4-5-year resident started to perform Supine PCNL for the first time while previously performing prone PCNL.

RESULTS

Access, fluoroscopy, and operation time were higher in Group 1, shorter in Group 2, and shortest in Group 3 (p < 0.001). Postoperative length of stay and the need for additional treatment were found to be shorter (p < 0.001), and the stone-free rate (SFR) increased (p < 0.001) from Group 1 to Group 3. The highest complication rates were observed in Group 1 (p = 0.002). SFR rate increased as the number of cases increased in Group 1 patients. Success was stable after 46-60 cases in terms of SFR. In Group 2, the SFR rate was stable after 31-45.

CASES

The most complications were observed in Group 1 and the least in Group 3.

CONCLUSION

In 2-3-year residents, access time and fluoroscopy time decrease with experience. In 4-5-year residents, due to their expertise in prone PCNL, the operation time and fluoroscopy time decrease with the number of cases performed. SFR is higher after 46-60 cases for 2-3-year residents and 31-45 cases for 4-5-year residents.

Renal Access in Pediatric Supine Miniaturized Percutaneous Nephrolithotomy: Comparative Evaluation of Ultrasound-Fluoroscopy Combined and Biplanar (0°-90°) Fluoroscopic Techniques

Introduction: Ultrasound (US)-guided puncture has the benefits of avoiding radiation and limiting the risk of visceral injury. We aimed to evaluate the results of two different renal access techniques during pediatric supine mini percutaneous nephrolithotomy (smPCNL) in a comparative manner. Patients and Methods: Data obtained from pediatric patients undergoing smPCNL by single surgeon between September 2021 and 2023 were reviewed retrospectively. Children were divided into two groups namely; biplanar 0°-90° fluoroscopy (Group-F) and US-fluoroscopy combined (Group-C). In all cases, preoperative, operative, and postoperative findings were recorded. Success was defined as the determination of either no (complete stone-free status) or < 4 mm residual fragments (CIRF) on US and X-ray (postoperative 3rd month) images. Complications were evaluated according to modified Clavien-Dindo classification. Results: Data of 54 patients with a mean age of 8.6 years (Group-F = 30, Group-C = 24) are reviewed. In addition to the similar success rates in both groups (Group-F = 86.7% Group-C = 87.5% p = 0.928), similar minor complications were noted in the majority of the cases. No child required transfusion and/or angioembolization. Although the fluoroscopy and operation time were lower in Group-C, the difference was not statistically significant. Conclusion: US-fluoroscopy combined access technique can be applied with similar success and complication rates in pediatric smPCNL. Ultimately, as experience is gained, this technique may lower radiation exposure, although this was not observed in the current study.

Adopting ultrasound guided PCNL in nephrolithiasis management

INTRODUCTION

This study aimed to evaluate the learning curve associated with the adoption of US guided PCNL and demonstrate that it can be carried out safely with results comparable to those obtained using standard PCNL.

METHODS

Prospective study with 65 patients who underwent PCNL between 2019 and 2020. all procedures were performed in supine position and an initial attempt to gain access to the kidney using US was made.

RESULTS

Mean procedure duration was 69.5 ± 27.8 min. Fluoroscopy was used with a mean dose of 276.68 ± 560.71 (cGycm3) and mean fluoroscopy time 40.25 ± 77.69 (s). Throughout the study there was a steady decrease in the use of fluoroscopy and amount of radiation to gain access to the kidney to only 25% at the study end. 76.5% of the patients were stone free at follow-up. Complication rate was 9.2%.

CONCLUSIONS

Fluoroless US guided PCNL is safe, feasible and reproducible procedure.

Advances in percutaneous renal puncture: a comprehensive review of the literature

PURPOSE OF REVIEW

Percutaneous nephrolithotomy (PCNL) constitutes the gold standard procedure for patients suffering from more than 2 cm renal stones. The puncture is a very critical step of PCNL, affecting manoeuvrability of the nephroscope, possibility to remove stone fragments, risk of bleeding and radiation exposure. The aim of the current review was to discuss the advances in percutaneous renal puncture.

RECENT FINDINGS

Following technological evolution in medicine, there was a consistent development in the puncture techniques, aiming at the improvement of its efficacy and safety. The use of specific agents can improve ultrasonic guidance, making the challenging step of gaining access to the kidney easier for the experienced surgeon and more accessible for the resident urologist. Future developments in the electromagnetic and three-dimensional (3D) technology may establish a high level of accuracy with decreased rates of related complications, even in the hands of beginners.

SUMMARY

The advances in percutaneous puncture can lead to improved safety and accuracy of this procedure decreasing the radiation exposure and the complication rate.

Electromagnetic-guided puncture: a tool or a tale?

PURPOSE OF REVIEW

The puncture technique and site of the puncture can impact the clinical outcome and the development of postoperative adverse events following percutaneous nephrolithotomy (PCNL). The aim of the current review was to discuss the available puncture guidance approaches and outline the potential role of the recently introduced electromagnetic-guided method.

RECENT FINDINGS

The puncture and PCNL tract establishment is usually performed using fluoroscopic or ultrasound guidance or a combination of two approaches. Electromagnetic-guided puncture is one of the most recent advancements of technology. The puncture navigation to the renal collecting system is available after placing a special wire with an electromagnetic tracking sensor into the desired calyx through the flexible ureterorenoscope. The available experimental and clinical studies have shown a high first puncture rate, decreased median time for obtaining a puncture, and shorter learning curves for beginners.

SUMMARY

Fluoroscopic and ultrasound guidance are the main approaches used by urologists. However, these modalities require a steep learning curve, approximately 60 cases for reaching competency. The initial data on electromagnetic navigation have shown the feasibility and potential promising outcomes of this novel approach. New studies are required to investigate its potential implementation opportunities in the daily practice of urologists.

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.

Case selection and implementation of tubeless percutaneous nephrolithotomy

Background

The tubeless percutaneous nephrolithotomy (PCNL) was proposed to eliminate the side effects of the nephrostomy tube in recent years, such as pain, channel infection, postoperative bleeding, and longer hospital stay. But there is neither clinical guidelines nor consensus about tubeless PCNL in clinical practice. The study is aimed to how to implement the tubeless PCNL step by step, including case selection preoperatively, improving the technique of the surgeon, making the correct decisions at the end of the procedure, which had not been previously examined.

Methods

From January 2017 to March 2018, 364 consecutive patients requiring PCNL were comprehensively analyzed preoperatively and patients were selected for scheduled tubeless PCNL based on four aspects. The selected patients were divided into two groups according to whether the nephrostomy tube was finally placed. The mean operative time, intraoperative blood loss, stone clearance rate, visual pain score, postoperative hospitalization days and perioperative complications were all evaluated.

Results

Based on the preoperative evaluation, 42 patients were selected for tubeless PCNL, among which there were finally 37 cases of completed tubeless PCNL. Compared with patients undergoing conventional PCNL, there were not statistical differences in the mean operative time (P=0.207) or intraoperative blood loss (P=0.450) in the tubeless group. Stone clearance rate was 100% in both groups. The visual pain scores in the tubeless PCNL group were lower on operation day (P=0.029), first postoperative day (P<0.001) and the day of discharge (P=0.025). The postoperative hospitalization for the tubeless PCNL group was shorter than that of the control group (P<0.001). No significant difference in grade 1 complications was seen (P=0.424), and no grade 2 or higher complications were observed in either group.

Conclusions

Postoperative pain was significantly relieved and postoperative hospitalization was significantly shortened in the tubeless PCNL group. Tubeless PCNL is safe if patients are carefully selected using four criteria before operation, attention is paid to four key points and five confirmations are made during operation.

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.

The Outcomes of Minimally Invasive Percutaneous Nephrolithotomy with Different Access Sizes for the Single Renal Stone ≤25 mm: A Randomized Prospective Study

OBJECTIVES

The aim of this study was to provide a randomized controlled trial comparing the outcomes of different access sizes used in the solo ultrasonic-guided minimally invasive percutaneous nephrolithotomy (mini-PCNL).

METHODS

From January 2018 to December 2019, a total of 160 cases with single renal stones of <25 mm were randomized to undergo mini-PCNLs with Fr16, Fr18, Fr20, or Fr22 accesses. All accesses were established with the axis of the target calyx as the marker for puncture location and then expanded to the desired size. Hemoglobin reduction, operative time, stone-free rate, complications, etc., were all recorded and assessed.

RESULTS

The demographic data were similar, and there were no significantly intergroup differences in stone-free rate, complications, and hospital stay time. The hemoglobin reduction was comparable and was 0.9 ± 0.6, 0.9 ± 0.7, 1.0 ± 0.5, and 1.1 ± 0.7 g/dL for the groups Fr16, Fr18, Fr20, and Fr22, respectively. The operative time was 53.4 ± 14.5, 48.5 ± 15.2, 42.8 ± 13.3, and 43.3 ± 13.1 min for the 4 groups, which decreased significantly from group Fr16 to Fr20, but there was no significant difference between Fr20 and Fr22 groups.

CONCLUSIONS

The axis of target calyx is a reliable marker for establishment of percutaneous renal access under ultrasonic guidance. The surgical outcomes of different access sizes were comparable, but the operation time was significantly shortened with the increase of size. However, Fr22 was not more efficient than Fr20.

An Assessment of the Impact of Flow Disruptions on Mental Workload and Performance of Surgeons During Percutaneous Nephrolithotomy

Objective

The aim of this study was to assess the impact of intraoperative disruptions on surgeons’ workload and performance during percutaneous nephrolithotomy (PCNL).

Materials and methods

A structured and standardized tool was used to identify disruptions and interferences that occurred during 33 PCNL procedures. The surgical steps during PCNL were divided into four phases: ureteric catheter placement (phase I), puncture and tract dilation (phase II), intra-calyceal navigation and stone fragmentation (phase III), and tube placement (phase IV). Surgeons’ workload was evaluated using a validated tool: Surgery Task Load Index (SURG-TLX), and correlated with the mean observed intraoperative disruptions. All operating team members evaluated the teamwork immediately after the procedure. Statistical analysis was performed using SPSS Statistics version 22 (IBM, Armonk, NY).

Results

A total of 1,897 disturbances were observed, with an average of 57.48 ± 16.36 disruptions per case. The largest number of disruptions occurred during phase III of PCNL (32.06 ± 14.12). The most common cause of the disruption was people entering or exiting the operating room (OR) (29.1 ± 10.03/case), followed by the ringing of phones or pagers (6.42 ± 2.4). The mean observed intraoperative disruptions were significantly associated with the operating surgeon’s mental workload, and it had a significant impact on all domains of surgeons’ mental workload as measured by SURG-TLX. Compared to other team members, surgeons’ assistants experienced an inferior sense of teamwork (r=-0.433; p=0.012).

Conclusion

Significant intraoperative disruptions were observed during PCNL. They were observed to directly correlate with the surgeon's workload and had a detrimental effect on teamwork. Improving OR dynamics by reducing unnecessary disruptions would help establish an efficient and smooth surgical work environment for safe surgical care.

Simplified biplanar (0-90°) fluoroscopic puncture technique for percutaneous nephrolithotomy: the learning curve

PURPOSE

To evaluate the learning curve of the simplified fluoroscopic biplanar (0-90º) puncture technique for percutaneous nephrolithotomy.

METHODS

We prospectively evaluated patients with renal stones treated with percutaneous nephrolithotomy by a single institution's fellows employing the simplified bi-planar (0-90º) fluoroscopic puncture technique for renal access. The learning curve was assessed with the fluoroscopic screening time and the percutaneous renal puncture time. Data obtained were compared to a subset of patients operated by a senior surgeon.

RESULTS

Eighty-nine patients were included in the study. Forty patients were operated by fellow-1, 39 by fellow-2, and 10 patients by the senior surgeon. Demographic data of all patients between groups were homogeneous, with no difference in gender (p = 0.432), age (p = 0.92), stone volume (p = 0.78), puncture laterality (p = 0.755), and body mass index (p = 0.365). The mean puncture time was 7.5, 4, and 3.1 min for fellow-1, fellow-2, and expert, respectively. The mean fluoroscopic screening time for the puncture was 10, 11, and 5.1 s for fellow-1, fellow-2, and the expert, respectively. Stone cases, both fellows needed to complete 10 procedures to match the senior surgeon in the mean puncture time (p = 0.046); meanwhile, the fluoroscopic screening time was equal even before to complete 10 procedures.

CONCLUSION

This study suggests that with the simplified biplanar (0-90º) puncture technique, the fluoroscopic screening time used in the learning process is brief. A novice fellow could require to complete ten cases to flatten the learning curve treating complex stone cases, and a flat learning curve is seen since the beginning when treating simple renal stones.

Balloon versus Amplatz for tract dilation in fluoroscopically guided percutaneous nephrolithotomy: a systematic review and meta-analysis

OBJECTIVE

To compare the safety and efficacy of balloon and Amplatz for tract dilation in fluoroscopically guided percutaneous nephrolithotomy (PCNL).

METHOD

EMBASE, PUBMED, MEDLINE and the Cochrane Central Register of Controlled Trials were searched for pertinent studies up until 30 October 2019. Pooled effects were calculated as ORs with 95% CIs or mean differences (MD) with 95% CIs. Endpoints included postoperative decrease in haemoglobin, transfusion rate, complication rate, successful dilation rate, stone-free rate, fluoroscopy time, access time, total operation time and length of postoperative hospitalisation (LPH). Bonferroni's correction was intercalated to reduce the likelihood of making a meta-analytical false positive.

RESULTS

One randomised controlled trial and five controlled clinical trials were included, which involved 1317 patients in total. We found a lower drop in postoperative haemoglobin for patients receiving balloon dilation compared with those in the Amplatz group (MD=-0.21, 95% CI -0.33 to 0.09, p=0.0005; Bonferroni correction a=0.005). Access time in the balloon group was also, on average, 2.61 min shorter than the Amplatz group (MD=-2.61, 95% CI -4.20 to 1.01, p=0.001; Bonferroni correction a=0.005). No significant differences were identified between the two dilation methods in terms of transfusion rate, complication rate, successful dilation rate, stone-free rate, fluoroscopy time, total operation time and LPH.

CONCLUSION

Balloon dilation is a safe and effective tract dilation technique for access creation during fluoroscopically guided PCNL. Both of methods have similar success rates although balloon dilation is associated with significantly less postoperative haemoglobin decline and shorter access time. Therefore, balloon dilation appears to be the superior tract dilation technique, but further confirmatory research is required to confirm these findings.

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.

Learning Curves in Urolithiasis Surgery: A Systematic Review

BACKGROUND AND AIMS

Procedures for urolithiasis are a core part of the development for the urologist in training. Understanding the learning curve of the procedures is important, allowing for planning in the training and assessment of trainees. The aim of this study was to systematically review the literature pertaining to learning curves in urolithiasis surgery.

MATERIALS AND METHODS

The review was registered on the PROSPERO database and conducted in keeping with the Preferred Reporting Items for Systematic reviews and Meta-Analysis statement. Embase, MEDLINE, and PsycINFO were systematically searched from inception to January 2018, with a reference review conducted. All empirical studies on learning curves in urolithiasis surgery were included irrespective of procedure. Articles describing pediatric surgery, nontechnical skills in surgery, or those not written in English were excluded.

RESULTS

Of 390 articles identified from screening, a final 18 studies were included. Fourteen studies identified the learning curve in percutaneous nephrolithotomy. These studies identified a learning curve of between 30 and 60 cases for both operative time (OT) and complication rates. Four articles focused on flexible ureteroscopy (FURS); the learning curve for FURS has been outlined as 60 cases for OT and 56 cases for fragmentation efficacy.

CONCLUSIONS

The complexities of determining learning curves are extensive; studies use different parameters to measure outcomes and observe skill acquisition rates of surgeons with differing prior experience. Evidence in this article can guide trainee urologists with regard to the expected rate of progress. Multi-operator multicenter research utilizing standard outcome measures should be conducted to establish definitive learning curves.

The Anatomic Structure of a Fused Renal Pyramid and Its Clinical Significance in the Establishment of Percutaneous Renal Access

OBJECTIVE

To explore the clinical significance of the fused renal pyramid (FRP) in establishing percutaneous renal access, and the anatomic basis for avoiding vascular injury caused by puncturing through this renal pyramid with the aim of achieving accurate puncture in percutaneous nephrolithotomy.

MATERIALS AND METHODS

Sixty-two cadaveric kidneys and 105 porcine kidneys were selected for the assessment of regional anatomy, to explore the anatomic structure of the FRP and determine its frequency. Then, we compared the effects of 4 different puncture paths on the occurrence of renal vascular injury when respectively punctured through the normal renal pyramid (group A), the centerline of one side pyramid of the FRP (group B), the center of the entire FRP (group C) and the renal column (group D).

RESULTS

The incidence of FRP in human kidneys is not low. The artery in the kidney can be divided into 6 grades. The grade IV branch-interlobar artery courses through the FRP. There was significant difference in the degree of arterial injury between the group A and C (P = .003), while no significant difference between the group A and B (P = .151). There was significant difference in the proportion of interlolar artery injury between group A and C (P <.001), while no significant difference between group A and B (P = .239).

CONCLUSION

It is necessary to carefully identify and bypass the FRP when establishing a percutaneous renal access. If unavoidable, the puncture path should be on the centerline of one side pyramid of the FRP.