Ureteral Access Sheath Insertion Research Articles

Preoperative α1-Blockers Impact on Outcomes of Patients Undergoing Ureteroscopy with Ureteral Access Sheaths: A Systematic Review and Meta-Analysis.

Introduction: The use of a ureteral access sheath (UAS) during ureteroscopy (URS) has been associated with the risk for ureteral injuries. Preoperative administration of α1-blockers presents a potential mitigator of such lesions by inducing ureteral relaxation, which may also contribute to improving other surgical outcomes. Methods: A comprehensive literature search was conducted across MEDLINE, Embase, and Cochrane databases for studies comparing preoperative α1-blockers administration vs its non-use in adult patients without pre-stenting undergoing URS. Binary outcomes were evaluated using risk ratios (RRs) and odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was measured with the Cochran's Q test, I2 statistics, and prediction intervals (PIs). A DerSimonian and Laird random-effects model was utilized for all outcomes. Results: Eleven studies encompassing 1074 patients undergoing URS were included, of whom 522 (48.60%) received α1-blockers before the procedure. Preoperative α1-blockers were associated with a reduction in significant ureteral injuries (RR 0.30; 95% CI 0.17-0.53; I2 = 6%; PI 0.10-0.88) and an increase in mean successful UAS insertion (OR 2.14; 95% CI 1.08-4.23; I2 = 23%; PI 0.51-8.93). In patients undergoing exclusively ureteroscopy lithotripsy (URSL), the medications also reduced total complications (RR 0.62; 95% CI 0.46-0.84; I2 = 0%) and complications graded Clavien-Dindo III or higher (RR 0.16; 95% CI 0.04-0.69; I2 = 0%), but no significant difference between groups was found in the stone-free rate (RR 1.10; 95% CI 0.86-1.40; I2 = 91%; PI 0.47-2.59). Conclusion: Preoperative α1-blockers were linked to a decrease in significant ureteral injuries with UAS use and fewer complications during URSL procedures. However, their impact on the successful insertion of a UAS remains uncertain. Consideration of administering preoperative α1-blockers in non-stented adult patients undergoing URS with UAS is advisable.

Does preoperative silodosin administration facilitate ureteral dilatation during flexible ureterorenoscopy? A randomized clinical trial

PurposeTo assess whether preoperative administration of silodosin can facilitate the placement of ureteral access sheath (UAS) prior to flexible ureteroscopy (F-URS) and reduce the occurrence of ureteric injury in challenging cases.MethodsThis prospective randomized clinical trial was carried out on 147 patients diagnosed with upper ureteric stone or stone kidney, non-stented. The patients were randomly divided into two equal groups. Group A (silodosin group) included patients in whom F-URS was done with daily preoperative intake of 8 mg silodosin for 1 week and group B (placebo/control group) included patients in whom F-URS was done with daily preoperative intake of placebo tablets.ResultsIn group A, a total of 23 (33.3%) experienced ureteral wall injury following UAS insertion, while in group B, this occurred in 40 patients (59.7%). There was a statistically significant difference in the grade of ureteral wall injury between the two groups (P < 0.001). In the multiple regression analysis, age, operative time and silodosin were found to be significant risk factors for ureteral wall injury (P = 0.007, 0.041 and < 0.001, respectively).ConclusionsThe administration of silodosin prior to retrograde intrarenal surgery (RIRS) effectively prevented significant ureteral wall damage and reduced initial postoperative discomfort.

A Good Craftsperson Knows Their Tools: Understanding of Laser and Ureter Mechanics in Training Urologists.

Introduction: Recent decades have seen a move to minimally invasive techniques to manage urolithiasis. Trainees are expected to develop competency in common endourology procedures. Knowledge of ureter mechanics and the theory behind new technologies is important to ensure safe and efficient techniques. We aim to evaluate the exposure to endourology, self-reported competency in common techniques and knowledge of basic ureter biomechanics and technology in training urologists. Methods: An online survey was circulated to all training urologists in the Republic of Ireland. Questions focused on self-reported competency, clinical knowledge, ureter mechanical properties and laser technology. Results: Thirty responses were received with a range of 1-8 years of urology experience (mean=4 years). The respondents reported high levels of exposure to endourology with the majority reporting competency in flexible ureterorenoscopy (FURS) (n=18, 60%) and semi-rigid ureteroscopy (URS) (n=21, 70%). The respondents demonstrated good clinical knowledge but variable knowledge of laser settings, laser thermodynamics and ureter mechanics. Half of the respondents (n=15, 50%) correctly described fragmentation laser settings, with 10 trainees (n=33%) accurately identifying both factors that increase ureteral access sheath (UAS) insertion force. Most of the respondents (n=20, 67%) described the proximal ureter as the site with the greatest compliance, while the site of the greatest force during ureteroscope insertion was correctly identified by 17% (n=5). Conclusion: To our knowledge, this represents the first study evaluating urologist understanding of laser technology and the mechanical properties of the human ureter. Despite trainees reporting high levels of experience in endourology, there is a variable understanding of the principles of laser technology and ureter mechanics. Further research and education are needed with a focus on laser safety, suitable laser settings and the safe limit of insertion forces.

Is It a Good Strategy to Proceed a Retrograde Intrarenal Surgery Session Sheathless After Ureteral Access Sheath Insertion Failure? A RIRSearch Study.

Objectives: To complement our previous findings regarding effect of ureteral access sheath (UAS) use, we checked RIRSearch database for patients who operated without using UAS. The aim of the study was to understand these new data better by comparing outcomes of retrograde intrarenal surgery (RIRS) that continued sheathless after a failed UAS insertion vs those planned and completed sheathless. Materials and Methods: Data of 195 patients who underwent sheathless RIRS for kidney and/or ureteral stones between 2011 and 2021 were retrieved from the database. Patients divided into two groups: cases who were planned and completed sheathless (n = 110, Group 1) and those who proceeded without UAS after insertion failure (n = 85, Group 2). After propensity score matching (PSM), each group consisted of 76 patients. Results: After PSM, stone-free rate for Group 1 (90.8%) was significantly higher than stone-free rate of Group 2 (76.3%) in sheathless RIRS (p = 0.02). Also postoperative complication rate was significantly lower in Group 1 (10.5%) than in Group 2 (27.6%) (p = 0.007). In Group 2, median operating time was longer (60 minutes, interquartile range [IQR]: 40-80) and more unplanned auxilliary procedure (22.4%) was needed than Group 1 (45 minutes, IQR: 40-50 and 3.9%) (both p = 0.001). Stone burden (odds ratio [OR]: 1.002, p = 0.019) and stone density (OR: 1.002, p = 0.003) were associated with high risk of residual stones after RIRS. Higher hydronephrosis grades were associated with increased stone-free rates (OR: 0.588 for residual stone risk, p = 0.024). Cases who completed sheathless by dusting all available stones, as planned preoperatively, were more likely to have stone-free status after RIRS than those who proceeded sheathless after UAS insertion failure (OR: 2.645, p = 0.024). Conclusions: Operation course after UAS insertion failure may be more challenging. In cases who performed without using UAS, surgeons who proceed with procedure sheathless after UAS insertion failure may more frequently run into complications and may fail achieving stone-free status compared with sheathless-planned cases.

Editorial Comment to Evaluation of ureteral injuries caused by ureteral access sheath insertion during ureteroscopic lithotripsy.

None declared.

Evaluation of ureteral injuries caused by ureteral access sheath insertion during ureteroscopic lithotripsy.

To evaluate ureteral injuries caused by insertion of a 13-Fr ureteral access sheath and identify factors (other than pre-stenting) that are predictive of ureteral injury. We enrolled 201 patients who underwent ureteroscopic lithotripsy (URSL). We excluded 80 patients who underwent ureteral stent insertion before URSL, 10 patients who did not use a ureteral access sheath, and 2 patients in whom a ureteral access sheath could not be inserted. In total, 109 patients were analyzed; all underwent insertion of a 13-Fr ureteral access sheath. We investigated ureteral injuries using the Traxer ureteral injury scale. There were 21 (19.3%) cases of ureteral access sheath-related ureteral injury, including 11 (10.1%) grade 2 cases and 10 (9.2%) grade 3 cases. The ureteral injury location was the proximal ureter in 20 cases (18.3%), middle ureter in one case (0.9%), and distal ureter in zero cases. Multiple logistic regression analysis showed that male sex and smaller stone diameter were significant predictive factors for ureteral injury (p=0.037, odds ratio [OR]: 5.19, 95% confidence interval [CI]: 1.11-24.3 and p=0.02, OR: 0.83, 95% CI: 0.71-0.97, respectively). Postoperative ureteral stricture did not occur in any cases. The rate of ureteral injury caused by a 13-Fr ureteral access sheath was considerable, and most ureteral injuries occurred in the proximal ureter. Male sex and smaller stone diameter were significant predictive factors for ureteral injury. The proximal ureter should be confirmed when using a 13-Fr ureteral access sheath, particularly in male patients and patients with small stones.

Preoperative alpha-blockers to facilitate ureteral access sheath (UAS) insertion: a systematic review and meta-analysis

Background: Recent studies have proposed the use of preoperative alpha-blockers to facilitate urethral access sheath (UAS) placement, but the definite role of this practice is still unclear. We aimed to evaluate the efficacy and safety of alpha-blocker use for UAS placement in intrarenal endoscopic procedures. Methods: The course of this study followed the preferred reporting items for systematic review and meta-analyses guidelines. Articles investigating the use of preoperative alpha-blockers for patients who underwent intrarenal endoscopic procedures were systematically reviewed from PubMed, EMBASE, and Scopus databases. Odds ratio (OR) with 95% confidence intervals (CIs) were applied for the outcome estimates. Analyses were performed with RevMan 5.4 software. The protocol of this study is enlisted in the registry of PROSPERO (CRD42022342811). Results: Six articles comprising 462 study populations were included in the review. Meta-analysis on the success rate of UAS placement showed a significant advantage of the alpha-blocker group compared to the control group (OR: 3.83; 1.83-8.00; 95% CI; p = 0.0004). Ureteral wall trauma was higher in the control group (OR: 0.38; 0.17-0.84; 95% CI; p = 0.02). Furthermore, there was no clear association between the UAS size and the success rate of UAS insertion. Conclusion: Preoperative alpha-blockers may increase the success rate of UAS insertion while decreasing the risk of ureteral wall injury in intrarenal endoscopic procedures.

The dilemma of 12/14F ureteral access sheath (UAS) usage: a case control study

BackgroundThe insertion of a ureteral access sheath (UAS) is a frequent procedure during flexible ureteroscopy (fURS) to facilitate kidney stone treatment. The aim of this study was to investigate the influence of 12/14 French (F) UAS on fURS outcomes.MethodsWe performed a retrospective monocentric analysis of fURS procedures conducted at the Department of Urology (University Hospital Schleswig–Holstein, Lübeck, Germany) for kidney stone treatment via lithotripsy or basket stone retrieval between September 2013 and June 2017. Uni- and multivariate analyses were done with the help of RStudio (Version 1.0.136) software.ResultsIn total, 283 consecutive fURS were analyzed. UAS was applied in 98 cases (34.63%). The insertion of UAS was preferred in cases with multiple kidney stones and larger median maximal stone diameter (p < 0.05). UAS usage correlated with elevated radiation exposure in seconds (94 vs. 61; p < 0.0001), prolonged operation time in minutes (99 vs. 66, p < 0.0001), length of hospital stay over 48 h (LOS, 22.49% vs. 10.81%; p = 0.015), more frequent postoperative systemic inflammatory response syndrome (SIRS, 13.27% vs. 4.32%; p = 0.013) and lower postoperative stone-free rates (60.20% vs. 78.92%; p = 0.0013). Moreover, we conducted uni- and multivariate subgroup analysis for cases with multiple kidney stones (≥ 2) and comparable stone burden; UAS was inserted in 48.3% of these cases (71/147). On multivariate logistic regression, UAS insertion was statistically associated with prolonged operation time in minutes (101 vs. 77; p = 0.004). No statistical differences regarding radiation exposure, stone-free rates, postoperative SIRS rates or LOS were noted between UAS and non-UAS patients with multiple kidney stones of similar size (p > 0.05).Conclusions12/14F UAS does not seem to improve overall outcomes in fURS for kidney stones. In patients with multiple kidney stones it may be associated with elevated operation time without a clear benefit in terms of improved stone-free status or reduced perioperative complication rate. Further prospective randomized studies to specify the indications for UAS usage are urgently needed.

Effective ureteral access sheath insertion during flexible ureteroscopy: Influence of the ureteral orifice configuration.

We sought to determine the possible predictors for effective insertion of the ureteral access sheath (UAS) during flexible ureteroscopy (fURS) in virgin ureters and their impact on postoperative ureteral wall injury and the procedural outcome. A retrospective review of prospectively collected data was performed for all consecutive patients scheduled for fURS of virgin ureters at two tertiary care centers between 2018 and 2020. Demographics, stone characteristics, and perioperative data, including the configuration of the ureteral orifice (UO) over introductory guidewire insertion, were collected. Multivariate logistic regression was used to detect possible predictors of successful UAS insertion. In total, 128 patients who underwent primary fURS were included, with a mean age of 43.3±12.3 years and a stone burden of 12.3±6.9 mm. One hundred and ten patients (85.9%) achieved successful ureteral access insertion, including 81 (63.3%) without ureteral dilatation and 35 with dilation, of which 29 (22.7%) had a successful UAS afterward, while six failed. Total patients who underwent ureteral orifice dilatation were 35. 29 had a successful UAS afterward, while 6 failed. Patients who underwent successful UAS placement into virgin ureters were significantly older and had a lower body mass index (BMI). A tent-shaped UO over the guidewire led to successful UAS insertion. In multivariate regression analysis, cases with BMI <30 kg/m2 (odds ratio [OR] 1.89, 95% confidence interval [CI] 1.28-7.03) and those with a tent-shaped UO over the introductory guidewire (OR 6.60, 95% CI 3.8-7.2) maintained their significance to predict successful UAS insertion into virgin ureters. Nine patients (8.2%) had ureteral mucosal injuries, and the overall stone-free rate was 78.2%. Patients with normal BMIs and tent-shaped UOs over the introductory guidewires are more likely to achieve primary UAS insertion without the need for ureteral dilation.

Role of pre-operative ureteral stent on outcomes of retrograde intra-renal surgery (RIRS): systematic review and meta-analysis of 3831 patients and comparison of Asian and non-Asian cohorts.

To evaluate the outcomes of pre-stented (PS) versus non-pre-stented (NPS) patients who have undergone retrograde intrarenal surgery (RIRS) for renal calculi with subgroup analysis of Asian and non-Asian cohorts. Protocol is registered in PROSPERO, CRD42021261123. Eligible studies identified from four electronic databases. Meta-analysis was done to enumerate the outcomes of RIRS in between PS and NPS. Secondary sub-analysis was done to look for differences in outcomes in Asian and non-Asian cohorts. Fourteen studies involving 3831 patients (4 prospective, 10 retrospective studies) were included. PS patients experienced higher success rates of ureteral access sheath (UAS) insertion than NPS (RR 1.09, 95% CI 1.05-1.13, p < 0.00001). PS patients had lower risk of ureteral injuries from UAS placement (RR 0.69, 95% CI 0.50-0.96, p = 0.03). No significant differences in intra- and postoperative complications between two groups were found. Stone-free rate (SFR) outcomes for residual fragment (RF) cut-off of < 1mm and < 4mm favoured the PS patients (RR 1.10, 95% CI 1.04-1.17, p = 0.002 for < 4mm, RR1.10, 95% CI 1.02-1.19, p = 0.02 for < 1mm). In the subgroup analysis, PS Asian patients had similar SFR as NPS patients for SFR(< 4mm) but non-Asian population showed better outcomes in the PS patients for SFR(< 4mm) (RR 1.31, 95% CI 1.13-1.52, p = 0.0005). This meta-analysis suggests that pre-stenting results in a higher success for UAS placement, minimising intraoperative ureteric injury, with higher overall SFR for any RF cut-off in PS cohorts. In non-Asian cohort, significant differences occurred at SFR < 4mm but not for SFR < 1mm. No difference was seen in our Asian cohort for any SFR cut-off in both PS and NPS patients.

Different failure rates of insertion of 10/12-Fr ureteral access sheaths during retrograde intrarenal surgery in patients with and without stones.

PurposeThe aim of this study was to compare the failure rates of insertion of a 10/12-Fr ureteral access sheath (UAS) during retrograde intrarenal surgery (RIRS) in cases with and without stones and to analyze the risk factors for UAS insertion failure.Materials and MethodsA total of 640 RIRS cases (538 with and 102 without stones) were evaluated. The primary outcome of interest was the failure rate of insertion of a 10/12-Fr UAS. Associated risk factors were assessed using univariate and multivariate logistic regression analyses. Propensity score (PS) matching and inverse probability of treatment weighting (IPTW) were used to ensure the robustness of the results.ResultsThe overall failure rate of 10/12-Fr UAS insertion in the cases without stones was significantly higher than that in the cases with stones (39.2% vs. 7.2%; p<0.001), and was approximately 2.5 to 4 times higher after PS matching and IPTW. Multivariate logistic analyses showed that being in the group without stones and younger age were independent significant risk factors for insertion failure in both the PS-matched cohort (odds ratio [OR], 5.43; 95% confidence interval [CI], 2.16–13.6; and OR, 1.04; 95% CI, 1.01–1.07) and the IPTW-adjusted cohort (OR, 1.82; 95% CI, 1.14–2.90; and OR, 1.03; 95% CI, 1.01–1.04).ConclusionsThe incidence of 10/12-Fr UAS insertion failure during RIRS was higher in cases without stones than in those with stones. These results provide valuable information for surgeons to use during informed consent discussions with patients undergoing RIRS, especially patients without stones.

Does ureteral access sheath have an impact on ureteral injury?

Objective:To present a well-organized review about ureteral access sheath impact on ureteral injury.Materials and Methods:Systemic search on literature was done. Total of 3766 studies observed by two urologists and results were unified. A Prisma diagram was used for eliminating irrelevant studies and at the end of elimination process 28 studies were found eligible for this review.Results:Not only clinical studies but also comparative experimental animal studies show that there is no significant data to claim that ureteral access sheath insertion causes more ureteral injury. Pre-stented patients were found to be at lower risk for ureteral injury. Risk of progression to ureteral injury seems to be low even if ureteral injury occurs with insertion of ureteral access sheath.Conclusion:Summary of studies’ results indicate that use of ureteral access sheath doesn’t increase ureteral injury. This review may help understanding safety profile of ureteral access sheath on evidence-based level. There is not enough data to make a statement that ureteral access sheath prevents ureteral injury.

Failure of ureteral access sheath insertion in primary flexible ureteroscopy for renal stones: is there any relation with inflammation?

To investigate the relationship between failure to insert a ureteral access sheath (UAS) with inflammation and other clinical parameters in patients treated with flexible ureteroscopy for renal stones. This study included patients who underwent flexible ureteroscopy for the treatment of renal stones in our centre between 2015 and 2020. Patients who underwent any surgical procedure on the ipsilateral ureter and had a history of spontaneous stone passage were excluded. Patients were divided into two groups based on UAS insertion success (group 1) or failure (group 2). Both groups were compared with a view to clinical characteristics, preoperative neutrophil, lymphocyte, monocyte and platelet counts and ratios of these counts, all being considered inflammatory markers. A multivariate logistic regression analysis was performed to determine the independent variables affecting UAS insertion success. There were 113 (59.1%) patients in group 1, while group 2 consisted of 78 (40.9%) patients. The rates of male gender, coronary artery disease and preoperative ipsilateral hydronephrosis were significantly higher in group 2, while platelet counts and platelet-lymphocyte ratios were significantly lower. Our analysis revealed four independent predictors for UAS insertion failure: female gender (odds ratio [OR]=2.1) increased the rate of UAS insertion success, while hydronephrosis (OR=1.6), low platelet counts and PLR increased the rate of UAS insertion failure (OR=0.99, OR=0.98, respectively). Our results suggest that male gender and ipsilateral hydronephrosis are associated with increased UAS insertion failure. Although we found a relationship between relatively low platelet levels and UAS insertion failure, we think that further studies are needed to investigate this matter.

Safety and efficacy of sequential balloon dilation prior to ureteral access sheath insertion in nonstented patients undergoing ureteroscopy

Techniques such as ureteral access sheath placement and balloon dilation are utilized to facilitate ureteroscopy. A retrospective review was performed to evaluate the efficacy and complications from ureteral access sheath (UAS) placement with or without sequential ureteral balloon dilation (SBD) in non-prestented patients who underwent ureteroscopy with UAS with or without SBD for renal or proximal ureteral stones from February 2014 to April 2017. This was a two-surgeon series of 124 patients divided into groups of SBD + UAS or direct UAS placement. Postoperative complications included hematuria, fever, and flank pain. Successful UAS insertion rates and postoperative complication rates were statistically significantly higher in the SBD + UAS group (P = 0.01 and 0.023, respectively). The procedure time, emergency department return, and 6-week stone-free rates were not statistically different between the groups. In conclusion, SBD + UAS has a higher success rate of UAS insertion compared to direct UAS alone, allowing for same-setting ureteroscopy. However, SBD + UAS is associated with significantly higher rates of fever, flank pain, and hematuria. We conclude that SBD + UAS and direct UAS are equivalent.

Silodosin for Prevention of Ureteral Injuries Resulting from Insertion of a Ureteral Access Sheath: A Randomized Controlled Trial

BackgroundThe ureteral access sheath (UAS) is an ancillary device widely used by urologists, but acute ureter injury may occur following its insertion. Preoperative selective oral α1-blockers can reduce intraureteral pressure, and prevent ureteral wall injury during UAS insertion. ObjectiveTo compare perioperative data of patients who underwent flexible ureterorenoscopy (fURS) with UAS with and without premedication with silodosin. Design, setting, and participantsSingle-blind, 100 patients from a single institution who underwent retrograde intrarenal surgery for kidney and upper ureter stone removal were prospectively allocated from May 2018 to March 2019. InterventionThe experimental groups received silodosin for 3 d preoperatively. Outcome measurements and statistical analysisThe primary endpoint included ureteral injuries after UAS insertion that were assessed according to endoscopic classification. The secondary endpoint was an evaluation of whether premedication with silodosin had any effect on postoperative outcomes. Results and limitationsA total of 44 and 43 patients were randomly assigned to the control and experimental groups, respectively. Silodosin prevented significant postoperative ureteral injury involving the smooth muscle layer more successfully than in the control group (9.3% vs 27.3%; p = 0.031). There was no significant difference in the overall complication rate as determined by the modified Clavien-Dindo classification system and the computed tomography scan stone-free rate postoperatively. Patients who received silodosin before fURS reported lower pain scores than those in the control group using a visual analog scale (p = 0.009). Limitation included a lack of placebo comparison. ConclusionsOur data suggest that preoperative silodosin protects against significant ureteral injury related to UAS insertion during fURS and decreases postoperative pain level. Silodosin premedication might be an effective and safe technique to replace prestenting. Patient summaryWe investigated the preventive effect of an α-blocker against perioperative complication caused by ureteral access sheath inserted during flexible ureterorenoscopy. Taking silodosin before surgery prevented ureter wall injury during surgery and immediately improved postoperative pain.

Variation of Fluoroscopic Radiation Dose during Endourological Procedures for Renal Stones

Introduction: Fluoroscopic guidance is routine for endourological procedures like percutaneous nephrolithotomy and retrograde intrarenal surgery in vast majority of centers. It is used for the initial retrograde ureteral access to define the pelvicalyceal system, puncture of the desired calyx and dilatation of the tract, aid navigation of stones and calyces, and placement of guide wires and stents. Both the patient and operating staffs are exposed to the radiation during surgery. The purpose of this study is to measure that exposed fluoroscopic radiation dose during these procedures and make operating surgeons aware of their fluoroscopic habit.&#x0D; Materials and Methods: This is prospective observational study, who underwent percutaneous nephrolithotomy (n=60) and retrograde intrarenal surgery (n=43) in our institute between December 2017 and August 2018. Percutaneous nephrolithotomy was done in prone position with prior insertion of ureteric catheter. Retrograde intrarenal surgery was carried out with or without insertion of ureteral access sheath. Fluoroscopic time was taken from the insertion of the ureteric catheter or UAS to the completion of the procedure with double J stenting.&#x0D; Results: For percutaneous nephrolithotomy and retrograde intrarenal surgery group, mean stone size were 21.89 mm and 10.56 mm; mean fluoroscopic time were 117.95 s (range 24-350) and 31.83 s (range 3-103); mean fluoroscopic dose were 29.71 mGy and 6.19 mGy respectively.&#x0D; Introduction: Fluoroscopic guidance is routine for endourological procedures like percutaneous nephrolithotomy and retrograde intrarenal surgery in vast majority of centers. It is used for the initial retrograde ureteral access to define the pelvicalyceal system, puncture of the desired calyx and dilatation of the tract, aid navigation of stones and calyces, and placement of guide wires and stents. Both the patient and operating staffs are exposed to the radiation during surgery. The purpose of this study is to measure that exposed fluoroscopic radiation dose during these procedures and make operating surgeons aware of their fluoroscopic habit.&#x0D; Materials and Methods: This is prospective observational study, who underwent percutaneous nephrolithotomy (n=60) and retrograde intrarenal surgery (n=43) in our institute between December 2017 and August 2018. Percutaneous nephrolithotomy was done in prone position with prior insertion of ureteric catheter. Retrograde intrarenal surgery was carried out with or without insertion of ureteral access sheath. Fluoroscopic time was taken from the insertion of the ureteric catheter or UAS to the completion of the procedure with double J stenting.&#x0D; Results: For percutaneous nephrolithotomy and retrograde intrarenal surgery group, mean stone size were 21.89 mm and 10.56 mm; mean fluoroscopic time were 117.95 s (range 24-350) and 31.83 s (range 3-103); mean fluoroscopic dose were 29.71 mGy and 6.19 mGy respectively.&#x0D; Conclusions: Among the endourological procedures for renal stones, retrograde intrarenal surgery was associated with less fluoroscopic hazard than percutaneous nephrolithotomy. Awareness of fluoroscopic exposure duration and experience of a surgeon can minimize the radiation hazard during endourological procedures.

A presumptive role of lower ureteral angles in the difficulty of ureteral access sheath insertion during retrograde intrarenal surgery

We aimed to investigate whether the angle created by the most lateral portion of the lower ureter is responsible for the difficulty in ureteral access sheath insertion. All male patients scheduled to undergo flexible ureteroscopy were enrolled. Patients with ureteral stricture in any course of the ureter and patients with problems at the ureteral opening were excluded. We set the coordinates of the most lateral portion of the lower ureter as M (x, y, z) using computed tomography. The bladder outlet was marked as the zero point O (0, 0, 0). The vector that passed through the urethra and point O was expressed as Vuo (0, 0, -u). The vector that passed through points O and M was expressed as Vom (x, y, z). Thus, an angle (90°-α) could be calculated between Vuo and Vom using the rotation angle formula. A total of 671 male patients were enrolled, among whom the ureteral access sheath could not pass through the most lateral portion of the lower ureter in 14 patients. The mean values of the α angle were 38.56° and 48.48° in the patient and control groups, respectively, compared with the 42 age- and sex-matched control subjects (p < 0.001). The ureteral angle determined by the level of the bladder outlet and the most lateral portion of the lower ureter could be a causative factor for the failure of ureteral access sheath insertion.

Failure of ureteral access sheath insertion in virgin ureters: A retrospective tertiary care center study.

Objective:The objective of the study was to identify the failure rate of insertion of ureteral access sheath (UAS) during primary flexible ureteroscopy (FURS).Materials and Methods:This was a single-surgeon, single-tertiary care center retrospective study. All patients who underwent primary FURS for proximal ureteric or renal stones from November 2014 to May 2018 were included in the study. Patients with a stone burden of more than 20 mm were excluded from the study. A 10/12-Fr coaxial UAS (Bi-Flex, Rocamed) was used. Data collection included age, sex, body mass index (BMI), stone burden and location, previous spontaneous passage of stones, type of anesthesia, and preexisting congenital anomalies. The Chi-square test and t-test were used for the statistical analyses.Results:One hundred and twelve patients were included in the study. All patients underwent primary FURS. The failure rate of primary UAS insertion was 10.7% (n = 12). No statistically significant difference was found in age, BMI, type of anesthesia, previous history of spontaneous stone passage, and stone burden between the success and failure groups (P > 0.05).Conclusions:We believe that our study opens the door for a multicentric prospective trial. Identifying factors leading to a failed primary FURS and UAS insertion is crucial to properly counsel patients preoperatively about the number of procedures that they might need and to prevent the financial loss associated with failed UAS insertion.

PT064 - Efficacy and safety of ultrasonic longitudinal-axis vibration for the reduction of ureteral access sheath insertion force: A randomized controlled trial in a porcine model

PT064 - Efficacy and safety of ultrasonic longitudinal-axis vibration for the reduction of ureteral access sheath insertion force: A randomized controlled trial in a porcine model

Efficacy and Safety of Ultrasonic Longitudinal-Axis Vibration for the Reduction of Ureteral Access Sheath Insertion Force: A Randomized Controlled Trial in a Porcine Model.

Excessive bulking force during ureteral access sheath (UAS) placement may induce injury. The sliding friction between surfaces can be reduced with the application of ultrasonic vibration. We investigated the efficacy and safety of an ultrasonic vibration transducing device for reducing the maximal ureteral access sheath insertion force (UASIF). A device was developed for transducing ultrasonic longitudinal-axis vibration onto the UAS at an adjustable amplitude and frequency while measuring the degree of UASIF. In the pilot study, six porcine models were used to investigate the optimal amplitude and frequency of vibration and to calculate sample size. Twelve porcine models were utilized in a randomized controlled trial. Resected ureters were pathologically evaluated for ureteral injury. The transduction of ultrasonic vibration at an amplitude of 0.04 g and a frequency of 18,000 Hz resulted in a maximal UASIF reduction of 36.4% (interquartile range 32.7-43.1). Maximal UASIF tended to decrease with increasing vibration frequency. No significant differences in UASIF reductions were observed according to amplitude. In the randomized controlled trial, the maximal UASIF reduction was 37.0% (interquartile range 21.4-44.2). Grade II injury was pathologically diagnosed in 8.3% (1/12) of the ureters in both groups. The transduction of ultrasonic longitudinal-axis vibration onto the UAS reduces maximal UASIF and does not harm the ureter. Reducing the velocity of sheath insertion may further reduce maximal UASIF.