Endourologic Procedures of the Upper Urinary Tract and the Effects on Intrarenal Pressure and Temperature

Rise in intraluminal temperature during ureteroscopy: Is this a concern?

The global increase in urolithiasis prevalence has led to a shift towards minimally invasive procedures, such as retrograde intrarenal surgery, supported by advancements in laser technologies for lithotripsy. Pulsed lasers, particularly the holmium YAG and the newer thulium fiber laser, have significantly transformed the management of upper urinary tract stones. However, the use of high-power lasers in these procedures introduces risks of heat-related injury. Laser lithotripsy works through photothermal and photomechanical effects to fragment stones, but up to 96% of the laser energy is converted into heat, increasing the risk of thermal damage to the surrounding urothelial mucosa. Studies show that even at low-power settings, intrarenal temperatures can exceed the threshold for cellular injury, particularly in confined spaces like the ureter. This narrative review explores strategies to mitigate thermal injury, including optimizing laser settings, improving irrigation flow rates, and incorporating novel methods such as cold irrigation, controlling outflow resistance, and using suction. Understanding these approaches is crucial to enhancing patient safety during high-power laser lithotripsy procedures.

Acknowledging acute kidney disease following ureteroscopy and laser lithotripsy: results from a tertiary care referral center

BACKGROUND

Acute kidney disease (AKD) is a recently described syndrome consisting of kidney function abnormalities lasting less than 3 months. Little is known regarding AKD following ureteroscopy (URS) and laser lithotripsy.

OBJECTIVE

To evaluate the occurrence and evolution of AKD in stone patients treated with URS.

MATERIALS AND METHODS

Data from 284 patients treated with URS for urinary stones were retrospectively analyzed. According to the KDIGO 2020 criteria, AKD was defined as postoperative acute kidney injury (AKI) occurrence, estimated glomerular filtration rate (eGFR) decrease ≥ 35%, or serum creatinine (SCr) increase ≥ 50%. AKI was defined as SCr increase ≥ 0.3 mg/dL or ≥ 50%. AKD evolution was evaluated 60 days post-URS. Data were analyzed using descriptive statistics. Univariable (UVA) and multivariable (MVA) logistic regression analyses tested the association of patients' characteristics and perioperative data with the occurrence of AKD.

RESULTS

Overall, postoperative AKD occurred in 32 (11.3%) patients. Recovery from AKD was found in 26 (82%) patients and persistent AKD occurred in 6 (18%) patients. At UVA, age at surgery (p = 0.05), baseline SCr (p = 0.02), baseline CKD category (p = 0.006), Charlson comorbidity index (p = 0.01), operative time (p = 0.04) and postoperative complications (< 0.001) were associated with AKD. At MVA, CKD category (OR 2.99, 95% CI = 1.4-6.3; p = 0.004), operative time (OR 1.01, 95% CI = 1.001-1.018; p = 0.023) and postoperative complications (OR 3.5, 95% CI = 1.46-8.49; p = 0.005) were independent predictors of AKD.

CONCLUSIONS

AKD is a frequent complication in patients treated with URS. Moreover, AKD persists in a non-neglectable percentage of patients at medium-term follow-up. Therefore, nephrological assessment should be considered, especially in high-risk patients. Current findings should be considered for the peri-operative management of stone patients.

An In Vivo Assessment of a Novel Temperature Control Flexible Ureteroscope System for Monitoring and Controlling Intrarenal Temperature During Flexible Ureteroscopy

OBJECTIVE

To evaluate the efficacy of a novel temperature control flexible ureteroscope system in the precise monitoring and control of intrarenal temperature (IRT) during ureteroscopy.

METHODS

We developed a novel temperature control flexible ureteroscope system (PT-Scope), including a temperature-monitoring ureteroscope and a irrigation-suction platform for temperature regulation. A porcine thermometry model was established to observe temperature changes under varying holmium laser powers (10, 20, 30 W) and irrigation rates (0, 20, 50 mL/min), utilizing percutaneous nephrostomy thermometry and PT-Scope measurements, with subsequent evaluation of temperature variations at different distances from the laser fiber tip. A porcine kidney stone model was established while porcine was randomly assigned to two groups: In the temperature control group, PT-Scope was connected to the irrigation-suction platform with temperature regulation, while in the nontemperature control group without temperature regulation. Comparative analysis was performed to evaluate differences in IRT between the two groups.

RESULTS

Across various laser powers and irrigation rates, the temperature measurement capability of the PT-Scope was precise, demonstrating consistency with percutaneous nephrostomy temperature measurements. The temperature obtained from the PT-Scope reflect the temperature approximately 0.05 cm away from the fiber tip, whereas temperatures close to fiber tip were significantly higher. The peak temperature of the temperature control group vs nontemperature control group were 31.70 ± 2.609°C and 44.37 ± 3.318 °C, respectively (P < 0.01). The mean temperature of the temperature control group vs nontemperature control group was 27.40 ± 2.107 °C vs 35.9 ± 1.921 °C (P < 0.01).

CONCLUSION

PT-Scope has demonstrated the capability to precisely monitor and control IRT within a safe threshold.

Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

The purpose of this study was to measure and compare renal pelvic pressure (RPP) between prone and supine percutaneous nephrolithotomy (PCNL) in a benchtop model. Six identical silicone kidney models were placed into anatomically correct prone or supine torsos constructed from patient CT scans in the corresponding positions. A 30-Fr renal access sheath was placed in either the upper, middle, or lower pole calyx for both prone and supine positions. Two 9-mm BegoStones were placed in the respective calyx and RPPs were measured at baseline, irrigating with a rigid nephroscope, and irrigating with a flexible nephroscope. Five trials were conducted for each access in both prone and supine positions. The average baseline RPP in the prone position was significantly higher than the supine position (9.1 vs 2.7 mmHg; p < 0.001). Similarly, the average RPP in prone was significantly higher than supine when using both the rigid and flexible nephroscopes. When comparing RPPs for upper, middle, and lower pole access sites, there was no significant difference in pressures in either prone or supine positions (p > 0.05 for all). Overall, when combining all pressures at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position compared to the supine position (14.0 vs 3.2 mmHg; p < 0.001). RPPs were significantly higher in the prone position compared to the supine position in all conditions tested. These differences in RPPs between prone and supine PCNL could in part explain the different clinical outcomes, including postoperative fever and stone-free rates.

Safety and feasability of ureteroscopy for pediatric stone, in children under 5 Years (SFUPA 5): A French multicentric study

INTRODUCTION

Ureteroscopy (URS) can be proposed as first-line therapy for the management of pelvic stones from 10 to 20 mm and for lower ureteric stones in children. However, little is known about the success and the morbidity of URS in young children. Ureteroscopic treatment may present matters in young children because of the small size of the pediatric kidney and the small size of the collecting system.

OBJECTIVE

To assess safety and efficacy of URS for the treatment of urinary stones in children aged of 5 years or less.

STUDY DESIGN

After the institutional ethical board approval was obtained, we conducted a retrospective, analytic, multicentric study that included all URS performed between January 2016 and April 2022 in children aged of 5 years or less. In this non-comparative case series, anonymized pooled data were collected from 7 tertiary care centers of pediatric patients. Endpoints were the one-session SFR at 3 months and per and postoperatives complications. Descriptive statistics were applied to describe the cohort.

RESULTS

Eighty-three patients were included. For them, 96 procedures were performed at the median age of 3.5 years (IQR: 0.8-5) and median weight of 14 Kg (6.3-23). Median stone size was 13 mm (4-45). There were 65 (67 %) renal stones treated with flexible URS, most of which were in the renal pelvis (30 %) and in the lower calix (33 %). A ureteral access sheath was used in 91 % procedures. Preoperative ureteral stent was placed in 52 (54 %) of patients. None of patients had ureteral dilatation. The single-session SFR was 67.4 % (56.3 and 89.2 % for flexible URS and semi-rigid URS respectively) and children require 1.4 procedures to achieve complete stone clearance. The overall complication rate was 18.7 %, most of them were minor (Clavien I-II). Intraoperative perirenal extravasation (Clavien IIIb) due to forniceal rupture was documented in 6.2 % of cases, related to an increased intrapelvic pressure (IPP) performed in a closed pelvicalyceal system.

DISCUSSION

Pediatric urologists should be aware of forniceal rupture based on the presence of extravasation of contrast during endourological procedures especially when they have difficulties to reach lower caliceal stone in small patient.

CONCLUSION

URS in patients aged of 5 years or less, is a complex minimally invasive procedure with reasonable efficacy and low morbidity. Intrarenal stones treated by RIRS in young children carries the risk of additional procedures to complete stone clearance.

A Novel Hydrodynamic Design Greatly Improves the Debris Clearance Rate of Flexible Ureteroscopy

Objectives: To introduce a novel hydrodynamic design for a flexible ureteroscope that can increase stone debris clearance. Methods: Based on hydrodynamics, the new design allowed the ureteroscope to have six water jets. Fluid gushed from the six jets and would ultimately converge into an eddy. The safety and stone debris clearance efficiency were tested in a 3D-printed kidney model. Stone fragments between 0.5 and 1 mm were used to mimic the debris. A ureteroscope already approved for marketing was used as a control. Results: The new design did not change the local renal pressure and did not raise the whole renal pressure under irrigation at 80 or 100 mL/min but slightly raised it under irrigation at 120 mL/min. The pressures in the 2 g stone clearance procedures were 26.0, 33.1, and 37.5 cmH2O for the new design and 25.1, 30.2, and 39.3 cmH2O for the current design; in the 4 g stone clearance procedures, the pressures were 30.1, 37.2, and 40.0 cmH2O for the new design and 26.9, 30.8, and 39.8 cmH2O for the current design, all under conditions of 80, 100, and 120 mL/min irrigation, respectively. The new design significantly improved the stone clearance rate by ∼10-fold. It effectively cleared 2 and 4 g stones within 900 seconds under the three irrigation rates. In contrast, the current design cleared <10% of the stone debris in all tests. Conclusion: The new hydrodynamic design significantly improved the stone debris clearance rate without causing obviously increased renal pressure, and the improvement was maintained under different irrigation pressures and stone burdens.

Perceptions and Practice Patterns of Urologists Relating to Intrarenal Pressure During Ureteroscopy: Findings from a Global Cross-Sectional Analysis

Objectives: To explore beliefs and practice patterns of urologists regarding intrarenal pressure (IRP) during ureteroscopy (URS). Methods: A customized questionnaire was designed in a 4-step iterative process incorporating a systematic review of the literature and critical analysis of topics/questions by six endourologists. The 19-item questionnaire interrogated perceptions, practice patterns, and key areas of uncertainty regarding ureteroscopic IRP, and was disseminated via urologic societies, networks, and social media to the international urologic community. Consultants/attendings and trainees currently practicing urology were eligible to respond. Quantitative responses were compiled and analyzed using descriptive statistics and chi-square test, with subgroup analysis by procedure volume. Results: Responses were received from 522 urologists, practicing in six continents. The individual question response rate was >97%. Most (83.9%, 437/515) respondents were practicing at a consultant/attending level. An endourology fellowship incorporating stone management had been completed by 59.2% (307/519). The vast majority of respondents (85.4%, 446/520) scored the perceived clinical significance of IRP during URS ≥7/10 on a Likert scale. Concern was uniformly reported, with no difference between respondents with and without a high annual case volume (p = 0.16). Potential adverse outcomes respondents associated with elevated ureteroscopic IRP were urosepsis (96.2%, 501/520), collecting system rupture (80.8%, 421/520), postoperative pain (67%, 349/520), bleeding (63.72%, 332/520), and long-term renal damage (26.1%, 136/520). Almost all participants (96.2%, 501/520) used measures aiming to reduce IRP during URS. Regarding the perceived maximum acceptable threshold for mean IRP during URS, 30 mm Hg (40 cm H2O) was most frequently selected [23.2% (119/463)], with most participants (78.2%, 341/463) choosing a value ≤40 mm Hg. Conclusions: This is the first large-scale analysis of urologists' perceptions of ureteroscopic IRP. It identifies high levels of concern among the global urologic community, with almost unanimous agreement that elevated IRP is associated with adverse clinical outcomes. Equipoise remains regarding appropriate IRP limits intraoperatively and the most appropriate technical strategies to ensure adherence to these.

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 (R² = 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.