Intra-renal pressure and temperature during ureteroscopy: Does it matter?

Early clinical outcomes using a 6.3 Fr single use ureteroscope compared to a 7.5 Fr device

Flexible ureteroscopy is a cornerstone in minimally invasive urology, providing effective management of kidney stones and other urological conditions. The emergence of single-use ureteroscopes addresses challenges associated with reusable devices, such as cross-contamination, maintenance costs, and degradation over time. This prospective, single-center study compared the performance of the 6.3 Fr single-use flexible ureteroscope to the 7.5 Fr model in the treatment of kidney stones ≤ 2 cm. Forty patients were divided into two groups of 20, with preoperative assessments including CT scans and urine cultures. All patients underwent flexible ureteroscopy with thulium fiber laser lithotripsy under general anesthesia, and stone-free rates (SFRs) were assessed via CT at one month postoperatively. The 6.3 Fr ureteroscope achieved a significantly higher SFR of 95% compared to 92.9% with the 7.5 Fr model (p = 0.042). Mean operative times were 58 min (6.3 Fr) vs. 62.5 min (7.5 Fr), with no statistically significant differences in laser time or total energy used. Energy efficiency was 0.047 mm3/J (6.3 Fr) vs. 0.035 mm3/J (7.5 Fr), while energy consumption was 20.89 J/mm3 vs. 28.34 J/mm3, respectively. Both devices exhibited low complication rates, with only minor complications (Clavien-Dindo grades 1 and 2) reported. Postoperative ureteral mucosal injury was assessed intraoperatively, and no cases exceeded Grade 1. This study highlights the safety and efficacy of the 6.3 Fr ureteroscope, demonstrating comparable or superior outcomes to the 7.5 Fr model in terms of SFR and operative time. While economic and sterility benefits were not evaluated, the findings support the adoption of smaller-diameter devices for minimally invasive procedures, though further studies are warranted to validate their broader clinical impact.

Concomitant catheter drainage alleviates the thermal effect of holmium lasers during ureteroscopic lithotripsy: a retrospective cohort study

BACKGROUND

Thermal control is pivotal for preventing ureter thermal injury during laser lithotripsy; however, patient-based studies have rarely addressed this topic. In recent years, we have employed a ureter catheter for irrigation drainage and measured temperature changes during lithotripsy. The aim of this study was to evaluate the thermal control effect of this strategy in ureteroscopic holmium laser lithotripsy.

METHODS

From September 2022 to June 2024, patients who underwent ureteroscopic holmium laser lithotripsy at our centre were included in this retrospective cohort study. Patients were divided into a drainage group and a conventional group depending on whether a ureter catheter was used for concomitant drainage during lithotripsy. The temperature was measured using a K-type thermocouple thermometer. Lithotripsy was performed at an irrigation pressure setting of 30 mmHg and a laser setting of 1.0 J × 20 Hz. Intraoperative and follow-up data were compared between the groups.

RESULTS

Sixty-seven patients were included, including 32 in the drainage group and 35 in the conventional group. lgCEM43 and the peak temperature of irrigation were significantly lower in the drainage group. The longest continuous lasing time was longer and the operation time was shorter than those in the drainage group. Compared with that in the conventional group, the quality of endoscopic vision in the drainage group during lithotripsy was significantly improved. There was no significant difference in the post-ureteroscopic lesion scale score or the 1-month stone-free rate between the groups. At the 6-month follow-up, no postoperative ureter stricture was observed in either group.

CONCLUSIONS

The current thermal control strategy is safe and feasible; it significantly reduces the intraoperative irrigation temperature and improves endoscopic vision in ureteroscopic laser lithotripsy.

Efficacy and safety of thulium fiber laser versus holmium: yttrium-aluminum-garnet laser in lithotripsy for urolithiasis: a systematic review and meta-analysis

This meta-analysis compares the efficacy and safety of thulium fiber laser (TFL) with holmium: yttrium-aluminum-garnet (Ho: YAG) laser in lithotripsy for urolithiasis. A literature search was conducted across PubMed, Embase, Web of Science, the Cochrane Central Register of Controlled Trials (CENTRAL), and ClinicalTrials.gov to identify studies published up to July 2024. Studies evaluating clinical outcomes for urolithiasis treated with either Ho: YAG laser or TFL were included. The meta-analysis, using RevMan 5.4 software, focused on comparing the stone-free rate (SFR) between the two lasers. A total of 21 studies were included. TFL was associated with a significantly higher SFR (RR 1.09, 95% CI: 1.02 to 1.16; P = 0.01), shorter operation time (SMD - 1.24, 95% CI: -1.82 to -0.66; P < 0.001), shorter lasing time (SMD - 1.26, 95% CI: -1.98 to -0.54; P < 0.001), shorter hospital stay (SMD - 2.08, 95% CI: -4.15 to -0.02; P = 0.05), reduced stone basket usage (SMD 0.50, 95% CI: 0.33 to 0.76; P = 0.001), and a lower total number of intraoperative complications (RR 0.67, 95% CI: 0.47 to 0.96; P = 0.03). However, TFL was also associated with a higher risk of postoperative sepsis (RR 5.32, 95% CI: 1.71 to 16.56; P = 0.004). Subgroup analyses revealed that TFL achieved a higher SFR in several subgroups, including ureteral stones, non-MOSES technology, and follow-up periods of ≥ 3 months, among others. In conclusion, TFL lithotripsy shows superior efficiency and safety compared to the Ho: YAG laser, though the increased risk of postoperative sepsis warrants further investigation.

Sheathless RIRS in the era of slim and single use flexible ureteroscopy (ssFURS): Prospective analysis of clinical outcome

INTRODUCATION

the purpose is to assess the feasibility of sheathless and time-limited retrograde intrarenal surgery (RIRS) using slim and single use flexible ureteroscopy (ssFURS) in view of the stone-free rate (SFR), complication rate and upfront ureteral stenting.

METHODS

A prospective, cross-sectional study of patients who underwent RIRS for kidney stones between December 2021 and December 2023 at our tertiary urology center was performed. Patient demographics, clinical presentations and stone characteristics were calculated. The SFR and complication rate were included.

RESULTS

Hundred and eighteen patients were included. The median age was 48 (35.7-60.0) years. Diabetes mellitus (DM) was present in 32 patients (27.1%). The median length of the kidney stones was 1.15 (range [0.4-3.0]), and the median width was 1 (range [0.05-3.7]). The pelvi-ureteric junction (PUJ) represented 75 (63.6%) patients. The lower pole stone (LP) consisted of 27 (22.9%) patients. Thirty-seven (31.4%) of the patients had multiple kidney stones. An overall complete SFR after the first session was observed for 94 (79.7%) patients. The second session of complete SFR was observed in 15 patients (12.7%). A median stone length of 1 (0.8-1.5) cm and a median stone width of 0.95 (0.7-1.3) cm were both significantly associated with a complete SFR after the first session (p < 0.001). A single kidney stone in 69 (73.4%) patients was significantly more strongly associated with a complete SFR after the first session than was multiple kidney stones in 25 (26.6%) patients (p = 0.027). Upfront stenting was performed in 74 patients (62.7%). The complete SFR after the first session was significantly greater in patients who underwent upfront stenting (65; 69.1%) than in those who underwent primary ssFURS (29; 30.9%, p = 0.004).

CONCLUSION

Sheathless and time-limited RIRS using ssFURS is a feasible and successful procedure with low complication rate.

Intrarenal Pressure in Retrograde Intrarenal Surgery: A Narrative Review

OBJECTIVE

To review the latest evidence on the complications of elevated intrarenal pressures (IRPs) in retrograde intrarenal surgery (RIRS) and the strategies to mitigate the increase of IRP during surgery.

METHODS

A comprehensive literature search of PubMed, Web of Science and EBSCO research databases was conducted from inception to July 31, 2024. The analysis involved a narrative review.

RESULTS

Normal physiological IRP in an unobstructed kidney ranges from 0 to 15 mmHg (0-20 cmH2O). During RIRS, dangerous IRPs are often reached, resulting in complications. These include pyelorenal reflux, which predisposes the patient to fever, urosepsis and postoperative pain, and forniceal rupture, which may result in intraoperative bleeding as well as acute kidney injury, postoperative pain, and fluid overload. To maintain safe IRP, outflow should be as close as possible to inflow. Minimizing the irrigation pressure by controlling the flow rate, reducing the pressure of the irrigant fluid, using a ureteral access sheath and maintaining an empty bladder during the procedure and, more recently, using real-time IRP monitoring are appropriate techniques to mitigate unsafe IRPs.

CONCLUSION

Several complications of RIRS are related to elevated IRPs, which cause pyelorenal backflow and forniceal rupture. Irrigation flow and pressure dynamics drive IRP changes during RIRS. Awareness of these factors will allow urologists to institute strategies to mitigate IRP during RIRS, thereby reducing complications and improving patient outcomes.

Recent advances in the treatment of renal stones using flexible ureteroscopys

Upper urinary tract stones are a common urological disease that can be treated by flexible ureteroscopy (FURS) through the natural urinary tract, in addition to extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy. The advantages of FURS are less trauma, faster recovery, and fewer complications, while its disadvantages include poor results of lithotripsy and stone extraction when dealing with larger stones, and prolonged operation time. Over the last two decades, the emergence of new technologies such as FURS combined with negative pressure suction, robot-assisted FURS, and artificially intelligent FURS, coupled with improvements in laser technology (the use of thulium fiber lasers and the invention of single-use flexible ureteroscopes (su-fURS) suitable for primary level application, have significantly increased the global adoption of FURS. This surge in usage holds a promising future in clinical application, benefiting a growing number of patients with renal calculi. Accompanied by changes in technical concepts and therapeutic modalities, the scope of indications for FURS is broadening, positioning it as a potential primary choice for urolithiasis treatment in the future. This review outlines the progress in employing FURS for the treatment of renal calculi in order to generate insights for further research.

Monitoring Intrarenal temperature changes during Ho: YAG laser lithotripsy in patients undergoing retrograde intrarenal surgery: a novel pilot study

Ho: YAG laser lithotripsy is widely used for urinary stone treatment, but concerns persist regarding its thermal effects on renal tissues. This study aimed to monitor intrarenal temperature changes during kidney stone treatment using retrograde intrarenal surgery with Ho: YAG laser. Fifteen patients were enrolled. Various laser power settings (0.8 J/10 Hz, 1.2 J/12 Hz) and irrigation modes (10 cc/min, 15 cc/min, 20 cc/min, gravity irrigation, and manual pump irrigation) were used. A sterile thermal probe was attached to a flexible ureterorenoscope and delivered into the calyceal system via the ureteral access sheath. Temperature changes were recorded with a T-type thermal probe with ± 0.1 °C accuracy. Laser power significantly influenced mean temperature, with a 4.981 °C difference between 14 W and 8 W laser power (p < 0.001). The mean temperature was 2.075 °C higher with gravity irrigation and 2.828 °C lower with manual pump irrigation (p = 0.038 and p = 0.005, respectively). Body mass index, laser power, irrigation model, and operator duty cycle explained 49.5% of mean temperature variability (Adj. R2 = 0.495). Laser power and operator duty cycle positively impacted mean temperature, while body mass index and specific irrigation models affected it negatively. Laser power and irrigation rate are critical for intrarenal temperature during Ho: YAG laser lithotripsy. Optimal settings and irrigation strategies are vital for minimizing thermal injury risk. This study underscores the need for ongoing research to understand and mitigate thermal effects during laser lithotripsy.

Temperature Measurements During Flexible Ureteroscopic Laser Lithotripsy: A Prospective Clinical Trial

Objective: The primary aim of the study was to explore intrarenal temperatures (IRTs) during flexible ureteroscopic laser lithotripsy (FURSL). The secondary aim was to investigate the correlation between temperatures and renal pelvis anteroposterior diameter (APD). Materials and Methods: From February 2023 to June 2023, 10 patients with an indwelling nephrostomy tube (NT) undergoing FURSL were enrolled in the study. Sheathless FURSL was performed using gravitational irrigation (23°C) at 60 cm. A sterile K-type thermocouple was inserted through the NT. Temperatures were recorded for 120 seconds with continuous laser activation and for another 60 seconds after deactivation. Thulium fiber laser delivered energy using a 150 μm fiber and incremental power settings of 5, 10, 20, and 30 W. The laser was deactivated whenever the IRT reached 43°C. Results: IRT correlated directly to power settings. Each time the power settings were increased, the temperature rose significantly. The increase in average peak temperature was 2.6°C between 5 and 10 W (p < 0.001), 3.4°C between 10 and 20 W (p < 0.001), and 2.5°C between 20 and 30 W (p < 0.001). Temperatures reached 43°C in three patients applying 20 W and in eight patients applying 30 W. The shortest activation-time until threshold was 12 and 28 seconds with 30 and 20 W settings, respectively. When reaching 43°C, temperatures remained above this threshold for an additional 29 seconds on average. There was a significant correlation between IRT and renal APD. For example, when 10 W was applied in the setting of APD ≤20 mm, the recorded temperature was on average 2.3°C higher compared with APD >20 mm, with the same power settings applied, p < 0.001. Conclusion: During FURSL, IRT correlates directly with power settings and is inversely correlated with renal pelvic APD. Using a sheathless approach, power settings ≥20 W should arguably be avoided, especially in the context of a nondilated renal pelvis. ClinicalTrials: The study was registered on ClinicalTrials.gov (NCT05677425).

Upper urinary tract pressures in endourology: a systematic review of range, variables and implications

OBJECTIVES

To systematically review the literature to ascertain the upper tract pressures generated during endourology, the relevant influencing variables and clinical implications.

MATERIALS AND METHODS

A systematic review of the MEDLINE, Scopus and Cochrane databases was performed by two authors independently (S.C., N.D.). Studies reporting ureteric or intrarenal pressures (IRP) during semi-rigid ureteroscopy (URS)/flexible ureterorenoscopy (fURS)/percutaneous nephrolithotomy (PCNL)/miniaturized PCNL (mPCNL) in the period 1950-2021 were identified. Both in vitro and in vivo studies were considered for inclusion. Findings were independently screened for eligibility based on content, with disagreements resolved by author consensus. Data were assessed for bias and compiled based on predefined variables.

RESULTS

Fifty-two studies met the inclusion criteria. Mean IRP appeared to frequently exceed a previously proposed threshold of 40 cmH₂ O. Semi-rigid URS with low-pressure irrigation (gravity <1 m) resulted in a wide mean IRP range (lowest reported 6.9 cmH₂ O, highest mean 149.5 ± 6.2 cmH₂ O; animal models). The lowest mean observed with fURS without a ureteric access sheath (UAS) was 47.6 ± 4.1 cmH₂ O, with the maximum peak IRP being 557.4 cmH₂ O (in vivo human data). UAS placement significantly reduced IRP during fURS, but did not guarantee pressure control with hand-operated pump/syringe irrigation. Miniaturization of PCNL sheaths was associated with increased IRP; however, a wide mean human IRP range has been recorded with both mPCNL (lowest -6.8 ± 2.2 cmH₂ O [suction sheath]; highest 41.2 ± 5.3 cmH₂ O) and standard PCNL (lowest 6.5 cmH₂ O; highest 41.2 cmH₂ O). Use of continuous suction in mPCNL results in greater control of mean IRP, although short pressure peaks >40 cmH₂ O are not entirely prevented. Definitive conclusions are limited by heterogeneity in study design and results. Postoperative pain and pyrexia may be correlated with increased IRP, however, few in vivo studies correlate clinical outcome with measured IRP.

CONCLUSIONS

Intrarenal pressure generated during upper tract endoscopy often exceeds 40 cmH₂ O. IRP is multifactorial in origin, with contributory variables discussed. Larger prospective human in vivo studies are required to further our understanding of IRP thresholds and clinical sequelae.

Role of Preoperative Ureteral Stent on Outcomes of Retrograde Intra-Renal Surgery (RIRS) in Children. Results From a Comparative, Large, Multicenter Series

OBJECTIVE

To assess outcomes of pre-stenting versus non-pre-stenting in children undergoing retrograde intrarenal surgery (RIRS) for intrarenal stones.

METHODS

Children/adolescent with kidney stones undergoing RIRS in 9 centers between 2015 and 2020 were retrospectively reviewed.

EXCLUSION CRITERIA

ureteral lithotripsy, bilateral procedures. Stone-free status was evaluated at 3-month and defined as a single residual fragment (RF) ≤2 mm/absence of multiple fragments. Patients were divided into two groups (Group 1 no-prestenting; Group 2 prestenting). Student's, Chi-square and Fisher's exact test was used to assess difference between groups. Univariable and multivariable logistic regression analysis were performed to predict RF. Statistical significance: P-value <0.05.

RESULTS

Three hundred eighty-nine children/adolescents were included (192 patients in Group 1). Prestented patients were younger compared with non-prestented (mean age 8.30 ± 4.93 vs 10.43 ± 4.30 years, P < 0.001). There were no differences in stone characteristics (number, size, locations). Lasing and total surgical time were similar. Urinary tract infections were more prevalent in Group 2 (10.7%) compared to Group 1 (3.7%, P = 0.016). Sepsis occurred in 2.1% of patients in Group 2 and no patient in Group 1 (P = 0.146). 30.7% patients in Group 1 and 26.4% in Group 2 had RF (P = 0.322). In univariate logistic regression analysis, stone size was associated with RF (OR 1.12 95%CI 1.06-1.18, P < 0.001), whereas Thulium fiber laser with a lower incidence (OR 0.24 95%CI 0.06-0.69, p=0.020). Multivariate logistic regression analysis showed that stone size was associated with RF (OR 1.20 95%CI 1.08-1.36, P = 0.001).

CONCLUSIONS

RIRS showed similar stone-free rate in pre and non-prestented children/adolescents, although prestented patients were younger. A higher risk of post-operative infections was reported in prestented patients.

Retrograde Intrarenal Surgery in Children: Evolution, Current Status, and Future Trends

Introduction: Incidence of urolithiasis in children has increased in recent years and with technological advancements and miniaturization of surgical instruments, pediatric urologists have acquired an impressive arsenal for their treatment. Retrograde intrarenal surgery (RIRS) has gained widespread popularity as it is a natural extension of semirigid ureteroscopy and can be done through natural orifice minimizing the morbidity of percutaneous access. The aim of this narrative review is to describe how RIRS has evolved over the decades in children and if the age-related anatomical difference impacts reported outcomes especially stone-free rate (SFR) and complications. Materials and Methods: An electronic literature search from inception to October 15, 2021 was performed using Medical Subject Heading terms in several combinations on PubMed, EMBASE, and Web of Science without language restrictions. A total of 2022 articles were founded and 165 articles were full-text screening. Finally, 2 pediatric urologists included 51 articles that summarize the available literature regarding the development and use of RIRS in children. Results: RIRS as of today is well established as a superior modality for all stones in all locations compared with extracorporeal shockwave lithotripsy both in children and adults. The passive dilation has decreased the need of active ureteral dilation, but the need to perform prestenting is not defined yet. Regarding the use of the ureteral access sheath, the literature tends to lean toward its placement in most cases, but we do not know its long-term effects over the growth of children. Finally, the SFR has increased as the experience of pediatric urologists increases, as well as the number of complications has decreased. Conclusion: RIRS in pediatrics has crossed many milestones, yet many areas need further research and larger data are required to make RIRS the procedure of choice for renal stone management in children across all age groups.

Advances in Ureteroscopy: New technologies and current innovations in the era of Tailored Endourological Stone Treatment (TEST)

Ureteroscopy has undergone many advances in recent decades. As a result, it is able to treat an increasing range of patient groups including special populations such as pregnancy, anomalous kidneys and extremes of age. Such advances include Holmium laser, high-power systems and pulse modulation. Thulium fibre laser is a more recent introduction to clinical practice. Ureteroscopes have also been improved alongside vision and optics. This article provides an up-to-date guide to these topics as well as disposable scopes, pressure control and developments in operating planning and patient aftercare. These advances allow for a custom strategy to be applied to the individual patient in what we describe using a new term: Tailored endourological stone treatment (TEST).

Level of evidence: 5

Temperature profiles during ureteroscopy with thulium fiber laser and holmium:YAG laser: Findings from a pre-clinical study

OBJECTIVE

The aim of this study was to investigate temperature profiles in both the renal pelvis and parenchyma during Thulium Fiber Laser (TFL) and Holmium:yttrium-aluminium-garnet (Ho:YAG) laser activation in an ex-vivo porcine model.

METHODS

Three porcine kidneys with intact renal pelvis and proximal ureters were used in the study. A temperature sensor was inserted through a nephrostomy tube into the renal pelvis and a second sensor was inserted directly into the renal parenchyma. Temperatures were recorded during continuous laser activation for 180 s, and for an additional 60 s after deactivation. TFL (150 μm and 200 μm) and Ho:YAG (270 μm) laser delivered power at settings of 2.4 W, 8 W, 20 W and 30 W.

RESULTS

Intrapelvic temperatures correlated directly to power settings. Higher power produced higher temperatures. For example, using a 150 μm fiber at 2.4 W resulted in a 2.6 °C rise from baseline (p = 0.008), whereas using the same fiber at 20 W produced a rise in temperature of 19.9 °C (p = 0.02). Larger laser fibers caused significantly higher temperatures compared to smaller fibers using equivalent power settings, e.g. mean temperature at 20 W using 150 μm was 39.6 °C compared to 44.9 °C using 200 μm, p < 0.001. There was a significant increase in parenchymal temperatures when applying 20 W and 30 W of laser power with the two larger fibers.

CONCLUSION

In this ex-vivo study, renal temperatures correlated directly to power settings. Higher power produced higher temperatures. Furthermore, larger laser fibers caused higher temperatures. These findings could help guide selection of safe power settings for ureteroscopic lithotripsy, but future clinical studies are needed for confirmation.

Flexible Ureteroscopy and Nephroscopy for Stone Removal in Patients with Multiple Renal Calculi

Objective

Renal calculi are a common type of urological calculi and are associated with morbidity. This study was aimed at exploring the effect of flexible ureteroscopy and nephroscopy on stone removal in patients with multiple renal calculi.

Method

This randomized controlled trial included a total of 78 cases with multiple renal calculi in our hospital. The patients were randomly divided into the study and control groups and treated with flexible ureteroscopy and percutaneous nephrolithotomy with pneumatic ballistics, respectively. The surgery condition, levels of prostaglandin F2α (PGF2α), prostaglandin E2 (PGE2), keratocyte growth factor (KGF), renal function indices, and the incidence of complications were analyzed before and after surgery in the two groups.

Result

The operation time, the postoperative analgesia pump application time, one-time stone removal rate, the intraoperative blood loss, and hospital stay of the study group were significantly lower than those of the control group. Postsurgery, the levels of PGE2, PGF2α, and KGF in the study group were significantly lower than those in the control group. The serum levels of SCR, BUN, and NGAL in the study group were significantly lower than those in the control group. In addition, the incidence complications in the study group were significantly lower.

Conclusion

Flexible ureteroscopy and laser lithotripsy under nephroscopy were equally effective against multiple renal calculi. Flexible ureteroscopy reduced surgical trauma without affecting renal function and had a low incidence of complications.

Intrarenal pressures during percutaneous nephrolithotomy: a porcine kidney model

BACKGROUND

Increased intrarenal pressure during endoscopic lithotripsy is associated with increased adverse outcomes. The objective of this study was to evaluate the effect of various devices on IRP during percutaneous intrarenal surgery in ex vivo porcine kidney models.

METHODS

Whole intact porcine urinary tracts were harvested. Intrarenal pressure was measured using cystometrometry software. Intrarenal pressure during PCNL was recorded using variations of percutaneous access sheath size, irrigation height of 100 cm and 60 cm, use of a ureteric catheter and use of suction. The primary outcome was absolute IRP measurements. Secondary outcomes were comparisons of IRP between techniques.

RESULTS

Using a 30 Fr vs 26 Fr access sheath and 26 Fr nephroscope the mean pressure at an irrigation height of 60 cm was significantly lower than 100 cm (p = 0.0013 vs p < 0.0001, respectively). Pressure's during mini-PCNL were significantly higher than conventional PCNL in all variations. Using the 16.5 Fr access sheath and 12 Fr nephroscope produced a significantly lower pressure at a 60 cm irrigation height than 100 cm (p = 0.0010). IRP was significantly lower with a ureteric catheter in place vs no ureteric catheter at 100 cm (p = 0.0015) and at 60 cm (p = 0.0040).

CONCLUSIONS

Using standard PCNL tract sizes intrarenal pressure varied significantly depending on the height of the irrigation fluid. Mini-PCNL is at higher risk of pathological pressure, however, the use of a ureteric catheter significantly decreased pressure. To maintain safe IRP during PCNL urologists should be aware of these significant variations.