Stone composition independently predicts stone size in 18,029 spontaneously passed stones

PURPOSE To evaluate whether the size of spontaneously passed stones (SPS) may be associated with clinical parameters. METHODS A search for SPS was conducted in our electronic stone database, comprising data on stones analyzed over the last 33 years at our institution. Adults with upper urinary tract stones were included. Cases with stenotic urinary tract disease or past history of anastomotic urinary tract surgery were excluded. Stone size expressed as maximal stone diameter (MSD) and stone volume (SV) was compared between groups by one-way ANOVA. Logistic regression analyses were performed to identify predictors of MSD ≥ 6 mm. RESULTS Overall mean MSD and SV for 18,029 SPS was 4.1 mm and 11.5 mm$^{3}$, respectively, and significantly differed between stone composition groups (p < 0.001). The lowest mean MSD and SV were found for calcium oxalate monohydrate (3.6 mm and 9.0 mm$^{3}$, respectively) and the highest mean MSD and SV were found for struvite (7.9 mm and 61.0 mm$^{3}$, respectively). Stone composition and increasing age were found to be independent predictors of MSD ≥ 6 mm (both p < 0.001). Sex differentiation did not contribute as a predictor of MSD ≥ 6 mm. CONCLUSIONS Stone composition and-to a lesser extent-age serve as independent predictors of size of spontaneously passed stones. Of particular importance, large spontaneously passed stones of ≥ 6 mm may be frequently found in cystine, brushite or struvite stone formers, whereas a minority of all calcium oxalate stones exceed that cutoff. Future studies shall evaluate these parameters as possible predictors of spontaneous stone passage

Predictors of Ureteral Strictures after Retrograde Ureteroscopic Treatment of Impacted Ureteral Stones: A Systematic Literature Review

BACKGROUND The stricture-formation rate following ureteroscopy ranges from 0.5 to 5% and might amount to 24% in patients with impacted ureteral stones. The pathogenesis of ureteral stricture formation is not yet fully understood. It is likely that the patient and stone characteristics, as well as intervention factors, play a role in this process. In this systematic review, we aimed to determine the potential factors responsible for ureteral stricture formation in patients having impacted ureteral stones. METHODS Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) criteria, we conducted systematic online research through PubMed and Web of Science without a time restriction, applying the keywords "ureteral stone", "ureteral calculus", "impacted stone", "ureteral stenosis", "ureteroscopic lithotripsy", "impacted calculus", and "ureteral strictures" singly or in combination. RESULTS After eliminating non-eligible studies, we identified five articles on ureteral stricture formation following treatment of impacted ureteral stones. Ureteral perforation and/or mucosal damage appeared as key predictors of ureteral stricture following retrograde ureteroscopy (URS) for impacted ureteral stones. Besides ureteral perforation stone size, embedded stone fragments into the ureter during lithotripsy, failed URS, degree of hydronephrosis, nephrostomy tube or double-J stent (DJS)/ureter catheter insertion were also suggested factors leading to ureteral strictures. CONCLUSION Ureteral perforation during surgery might be considered the main risk factor for ureteral stricture formation following retrograde ureteroscopic stone removal for impacted ureteral stones

Technique for supine percutaneous nephrolithotomy

Percutaneous nephrolithotomy is the gold standard for large kidney stones. Supine approach has proved to be safe and effective. Herein we present an educational video about our stepwise technique of supine PCNL in a safe way

Controversies in ureteroscopy: lasers, scopes, ureteral access sheaths, practice patterns and beyond

Ureteroscopy has become an increasingly popular surgical intervention for conditions such as urinary stone disease. As new technologies and techniques become available, debate regarding their proper use has risen. This includes the role of single use ureteroscopes, optimal laser for stone lithotripsy, basketing versus dusting, the impact of ureteral access sheath, the need for safety guidewire, fluoroscopy free URS, imaging and follow up practices are all areas which have generated a lot of debate. This review serves to evaluate each of these issues and provide a balanced conclusion to guide the clinician in their practice

Impact of Ureteral Stent Material on Stent-related Symptoms: A Systematic Review of the Literature

CONTEXT Ureteral stents are essential implants that are used on a daily basis. Since their invention, advances in stent design have been directed towards alleviating stent-related symptoms. It remains unclear how the material composition of the stent affects stent-related symptoms. OBJECTIVE To review the literature and define the clinical impact of ureteral stent material on stent-related symptoms. EVIDENCE ACQUISITION A literature search of the Embase, MEDLINE (PubMed), and Web of Science databases was conducted on December 17, 2021 to collect articles comparing stent composition materials regarding stent-related symptoms. Thirteen publications met the inclusion criteria, of which only one met the high-quality requirements of the Cochrane Collaboration tool for assessing the risk of bias in randomized trials. EVIDENCE SYNTHESIS Most trials, including the highest quality trial, seem to support that silicone double-J (DJ) stents reduce stent-related symptoms compared to nonsilicone DJ stents. Regarding physical properties, it seems that "soft" or "flexible" DJ stents reduce stent-related symptoms. However, since there was only one high-quality study with a low risk of bias, it is impossible to draw a definitive conclusion owing to the lack of quality data. CONCLUSIONS Silicone DJ stents, and by extension "soft" DJ stents, appear to reduce stent-related symptoms compared to nonsilicone polymers and "hard" DJ stents. No definitive conclusion can be drawn owing to a lack of quality evidence. Creating a standard for measuring and reporting physical stent properties should be the first step for further research. PATIENT SUMMARY A ureteral stent is a small hollow tube placed inside the ureter to help urine drain from the kidney. We reviewed the literature on the impact of stent material on stent-related symptoms. We found that silicone may reduce stent-related symptoms, but no definitive conclusion can be drawn and further studies are needed

Definition of clinically insignificant residual fragments after percutaneous nephrolithotomy among urologists: a world-wide survey by EAU-YAU Endourology and Urolithiasis Working Group

INTRODUCTION The aim of this article was to evaluate the current perception of urologists as to what size is considered as a clinically insignificant residual fragment (CIRF). MATERIAL AND METHODS A survey was globally distributed to the members of the Endourological Society via SurveyMonkey. RESULTS A total of 385 participants responded to the survey on CIRF. Most participants considered 2 mm (29%) as CIRF threshold, followed by 3 mm (24%), 4 mm (22%), 0 mm (14%), 5 mm (8%) and 1 mm (3%). North American urologists considered CIRF to be smaller than urologists from Asia, Eurasia and South America, (p-values ≤0.001, 0.037 and 0.015 respectively). European urologists identified smaller CIRF in comparison to Asian urologists (p-value = 0.001). Urologists mainly using a pneumatic lithotripter accepted larger fragments as CIRF, compared to urologists mainly using ultrasonic devices or a combination of ultrasonic and pneumatic devices (p-value = 0.026 and 0.005 respectively). Similarly, urologists mainly performing X-Ray and ultrasound as post-operative imaging accepted larger fragments as CIRF in comparison to urologists mainly performing non-contrast computed tomography (p-value = 0.001). CONCLUSIONS What is considered as CIRF varies between urologist from different continents and seems to be associated with the lithotripter used and the post-operative imaging modality of preference to assess treatment success

Illumination matters part IV: blackout and whiteout in flexible ureteroscopy - first report on a phenomenon observed by PEARLS

PURPOSE: To date, no study has evaluated effects of varying brightness settings on image quality from flexible ureteroscopes submerged in saline. The aim was to evaluate blackout and whiteout occurrences in an in-vitro kidney calyx model. MATERIAL AND METHODS: We evaluated a series of contemporary flexible ureteroscopes including the Storz Flex-Xc and Flex-X2s, Olympus V3 and P7, Pusen 7.5F and 9.2F, as well as OTU WiScope using a 3D-printed enclosed pink in-vitro kidney calyx model submerged in saline. Endoscopic images were captured with ureteroscope tip placed at 5 mm,10 mm and 20 mm distances. The complete range of brightness settings and video capture modes were evaluated for each scope. Distribution of brightness on a grayscale histogram of images was analyzed (scale range 0 to 255). Blackout and whiteout were defined as median histogram ranges from 0 to 35 and 220 to 255, respectively (monitor image too dark or too bright for the human eye, respectively). RESULTS: Blackout occurred with the P7, Pusen 7.5F, 9.2F and WiScope at all distances, and V3 at 20 mm - with lowest brightness settings. Whiteout occurred with Flex-X2s, V3 and P7 at 5 mm and 10 mm, as well as with V3 and P7 at 20 mm - mostly with highest brightness settings. The Flex-Xc had neither blackout nor whiteout at all settings and distances. CONCLUSION: Blackout or whiteout of images is an undesirable property that was found for several scopes, possibly impacting diagnostic and therapeutic purposes during ureteroscopy. These observations form a guide to impact a urologist's choice of instruments and settings

Instrumental dead space and proximal working channel connector design in flexible ureteroscopy: a new concept

OBJECTIVE The objective of this study was to evaluate a new concept in flexible ureteroscopy: instrumental dead space (IDS). For this purpose, various proximal working channel connector designs, as well as the impact of ancillary devices occupying the working channel were evaluated in currently available flexible ureteroscopes. DESIGN AND METHODS IDS was defined as the volume of saline irrigation needed to inject at the proximal connector for delivery at the distal working channel tip. Because IDS is related to working channel diameter and length, proximal connector design, as well as occupation of working channel by ancillary devices, these parameters were also reviewed. RESULTS IDS significantly varied between flexible ureteroscope models, ranging from 1.1 ml for the Pusen bare scopes, to 2.3 ml for Olympus scopes with their 4-way connector (p < 0.001). Proximal connector designs showed a high degree of variability in the number of available Luer locks, valves, seals, angles, and rotative characteristics. The measured length of the working channel of bare scopes ranged between 739 and 854 mm and significantly correlated with measured IDS (R$^{2}$ = 0.82, p < 0.001). The coupling of scopes with an alternative ancillary proximal connector and the insertion of ancillary devices into the working channel significantly reduced IDS (mean IDS reduction of 0.1 to 0.5 ml; p < 0.001). CONCLUSIONS IDS appears as a new parameter that should be considered for future applications of flexible ureteroscopes. A low IDS seems desirable for several clinical applications. The main factors impacting IDS are working channel and proximal connector design, as well as ancillary devices inserted into the working channel. Future studies should clarify how reducing IDS may affect irrigation flow, intrarenal pressure, and direct in-scope suction, as well as evaluate the most desirable proximal connector design properties

Illumination matters Part III: Impact of light obstruction on illuminance from flexible ureteroscopes - a comparative PEARLS analysis

PURPOSE: Artifacts from poor ureteroscopes' light design with shadowing and dark areas in the field of view have been reported. The aim was to quantify effects of light obstruction in a kidney calyx model. METHODS: We evaluated a series of contemporary flexible ureteroscopes including the Storz Flex-Xc and Flex-X2s, Olympus V3 and P7, Pusen 7.5F and 9.2F, as well as OTU Wiscope using an enclosed 3D-printed pink in vitro kidney calyx model submerged in saline, where the field of light was intentionally partially obstructed alternatively at 12, 3, 6, and 9 o'clock. A color spectrometer was used for illuminance measurements at a 45° opening position in the background of the model. RESULTS: Overall and mean background illuminance for each obstructive situation were significantly different between scopes for both 50% and 100% brightness settings (ANOVA p < 0.001). At 50% brightness setting, almost all scopes had their highest and lowest background illuminance with the 6 o'clock and 3 o'clock obstructive situation, respectively. At 100% brightness setting, these became 6 o'clock and 12 o'clock obstructive situations. Considering each obstructive situation individually, the Flex-Xc was consistently the scope with highest background illuminance and the Pusen 7.5F the lowest. Background illuminance for each obstructive situation varied significantly for each scope individually, with the greatest range of variability for Pusen 7.5F and V3. CONCLUSIONS: Illuminance performance of ureteroscopes within an obstructed calyx model differ significantly for various obstructive situations. Urologists should be aware of this to help guide their choice of ureteroscope