Roshan M. Patel

Background/Objectives: Emerging laser systems in endourology require further head-to-head trials to evaluate their ablation efficiency, or the amount of stone treated per energy spent. To answer this question, we built an in vitro model to compare stone ablation efficiency between the holmium:YAG with pulse modulation (Moses), pulsed thulium:YAG (pTm:YAG), and Thulium Fiber Laser (TFL) using dusting and fragmentation settings on uric acid (UA) and calcium oxalate monohydrate (COM) stones. Methods: We built an in vitro system with 24 UA and 18 COM stones fixed onto Petri dishes and submerged into warm saline. We used 200-micron laser fibers with settings of 0.3 J × 30 Hz for dusting and 1 J × 10 Hz for fragmenting. Each laser was fired while contacting the stone for 1 s per trial. Ablated stone volume was measured using Optical Coherence Tomography (OCT). A one-way Analysis of Variance (ANOVA) was conducted to determine differences in mean efficiency of laser fibers at different settings, with significance assessed at p < 0.05. Results: In total, 81 craters created by laser ablation were detected via OCT. When fragmenting UA stones, pTm:YAG was the most efficient, averaging 116.8 mm³/kJ, compared to 110.8 for TFL and 51.4 for Moses (p = 0.0003). There were no differences on the dusting setting for UA. TFL was the most efficient in fragmenting COM stones with 69.2 mm³/kJ, compared to 49.5 for pTm:YAG and 32.7 for Moses (p = 0.0024). Finally, pTm:YAG was the most efficient for dusting COM stones, with 30.5 mm³/kJ, compared to 23.8 for TFL and 14.5 (p = 0.0175). Conclusions: Pulsed Tm:YAG exhibited the most efficient fragmentation of UA stones and dusting of COM stones, while TFL was the most efficient for fragmenting COM stones.

Purpose In September 2024, flooding from Hurricane Helene shut down a Baxter Solutions facility, which produced ~ 60% of the United States’ intravenous fluids, resulting in a nationwide saline shortage. Hospitals subsequently restricted perioperative irrigation, including in percutaneous nephrolithotomy (PCNL), which traditionally relies on continuous saline irrigation throughout the procedure. We compared outcomes of PCNL under saline-restricted conditions with matched cases performed before the shortage. Methods Between October 15 and November 4, 2024, ten PCNLs were performed with recommendations to minimize irrigation. A matched control group was selected from a prospective institutional PCNL database, matched by age, sex, stone size, and operative time. Perioperative and postoperative outcomes—including irrigation volume, stone-free rate, laboratory values, and hospital length of stay—were analyzed using t-tests, Pearson chi-square, and Fisher’s exact tests. Results Mean irrigation volume was significantly lower in the saline-restricted group compared with controls (6,600 ± 4,852 mL vs. 19,125 ± 18,195 mL, p = 0.009). There were no significant differences in baseline demographics, stone volume, or operative time. The saline-restricted group had a shorter hospital length of stay (0.9 ± 0.3 days vs. 1.8 ± 1.8, p = 0.0462), and lower postoperative day 1 creatinine (0.9 ± 0.3 mg/dL vs. 1.3 ± 0.5 mg/dL, p = 0.026). Postoperative hemoglobin, hematocrit, residual stone burden, and residual stone grades were similar between groups. Conclusion PCNL performed under saline-restriction significantly reduced irrigation volume without adversely affecting early postoperative outcomes or residual stone burden. These findings support judicious saline use during PCNL, particularly in times of supply shortage.

Purpose of Review There is a high number of acute renal colic cases that present to the emergency department, and it is crucial to have reliable parameters that can accurately predict the likelihood of spontaneous stone passage. In this narrative review, we examined the latest data from the literature regarding the relationship between ureteral wall thickness and the probability of spontaneous stone passage. Recent Findings The thickness of a normal ureteral wall ranges between 0.95 and 2 mm, with an increase in thickness observed with advancing age. Current data suggests that thinner ureteral wall thickness may favor the spontaneous stone passage. However, the discrepancy between data from the literature is mainly caused by the small study cohorts, heterogeneous protocols, and the intra- and interobserver variability in evaluating non-contrast computed tomography results. Summary There remains a need to better understand the mechanisms behind stone expulsion, as current models rely on oversimplified assumptions about the ureter’s biomechanical properties.

Prior laser studies have demonstrated that as the temperature of a medium increases, the amount of energy delivered to the target increases. We sought to investigate the role of irrigation fluid temperature on Thulium fiber laser (TFL) urolith ablation. 360 calculi were divided in vitro according to chemical composition: calcium oxalate monohydrate (COM), cystine (CYS), struvite (STR), calcium phosphate (CAP), uric acid (UA), and calcium oxalate dihydrate (COD). A 200 μm TFL was placed directly on each stone, while immersed in 0.9% NaCl at four different temperatures (25 C, 37 C, 44 C, 60 C) and a single laser pulse administered at distinct energy settings (0.1 J, 0.5 J, 1.5 J). Optical coherence tomography assessed the resulting ablation cone volume. Mean stone volume and porosity were evaluated through ANOVA and Tukey post-hoc analysis. A multivariate generalized model for each composition accounted for the impact of fluid temperature and laser energy on stone ablation. Warmer fluid temperatures yielded greater ablation cone volumes for most energy settings, excluding UA stones. When accounting for chemical composition, higher tensile strength stones (COM, CYS) benefited most from warmer fluid in comparison to frangible stones (CAP, STR). The effects of increasing fluid temperature are modest relative to laser pulse energy as a large temperature increase (i.e. 7ºC) is equivalent to a minor energy increase (i.e. 0.1 J). For non-UA stones, TFL ablation efficiency increases with warmer irrigation fluid. The effect, albeit modest compared to laser pulse energy, was most notable for COM and CYS stones.

Purpose: Retrograde intrarenal surgery is the gold-standard treatment for most kidney stones. During ureteroscopy, ureteral access sheath insertion at forces greater than 8.0 Newtons (N) risks high-grade ureteral injury. To monitor force, our institution utilizes a unique, Bluetooth-equipped device (i.e., the University of California—Irvine Force Sensor). Given the unique nature of the force sensor, we sought to develop an inexpensive and accessible force sensor based on Boyle’s law and the specific amount of force required to compress an occluded 1.0 mL syringe. Materials and Methods: We evaluated three brands of 1.0 mL syringes. After setting the plunger at 1.0 mL, the syringe was occluded, and the syringe plunger was compressed. The syringe volume was recorded when the applied force on the plunger reached 4.0 N, 6.0 N, and 8.0 N. Multiple trials were performed to assess reliability and reproducibility. A method for applying this clinically was also developed. Results: The precise force thresholds identified for a 1.0 mL Luer-Lok™ Syringe (Becton Dickinson, Franklin Lakes, NJ) were 0.30 mL for 4.00 N, 0.20 mL for 6.00 N, and 0.15 mL for 8.00 N. The 1.0 mL Tuberculin Syringe and 1.0 mL Luer Slip Syringe were less precise, but compression from 1.0 to 0.40 mL, 0.25 mL, and 0.20 mL corresponded to force sensor readings that did not exceed 4.00 N, 6.00 N, and 8.00 N, respectively. Conclusions: Based on volume changes, 4.00 N, 6.00 N, and 8.00 N of force can be reliably and reproducibly achieved using an occluded 1.0 mL syringe.

Purpose: Ureteral access sheaths (UAS) pose the risk of severe ureteral injury. Our prior studies revealed forces ≤6 Newtons (N) prevent ureteral injury. Accordingly, we sought to define the force urologists and residents in training typically use when placing a UAS. Materials and Methods: Among urologists and urology residents attending two annual urological conferences in 2022, 121 individuals were recruited for the study. Participants inserted 12F, 14F, and 16F UAS into a male genitourinary model containing a concealed force sensor; they also provided demographic information. Analysis was completed using t -tests and Chi-square tests to identify group differences when passing a 16F sheath UAS. Participant traits associated with surpassing or remaining below a minimal force threshold were also explored through polychotomous logistic regression. Results: Participant force distributions were as follows: ≤4N (29%), >6N (45%), and >8N (32%). More years of practice were significantly associated with exerting >6N relative to forces between 4N and 6N; results for >8N relative to 4N and 8N were similar. Compared to high-volume ureteroscopists (those performing >20 ureteroscopies/month), physicians performing ≤20 ureteroscopies/month were significantly less likely to exert forces ≤4N ( p = 0.017 and p = 0.041). Of those surpassing 6N and 8N, 15% and 18%, respectively, were high-volume ureteroscopists. Conclusions: Despite years of practice or volume of monthly ureteroscopic cases performed, most urologists failed to pass 16F access sheaths within the ideal range of 4N to 6N (74% of participants) or within a predefined safe range of 4N to 8N (61% of participants).

Introduction: Electromotive drug administration (EMDA) amplifies drug delivery deep into targeted tissues. We tested, for the first time, the ability of EMDA to deliver methylene blue into the urothelium of the renal pelvis. Materials and methods: In an anesthetized female pig, both proximal ureters were transected two inches distal to the ureteropelvic junction. An 8Fr dual lumen catheter and a 5Fr fenestrated catheter with an indwelling silver wire were inserted into both renal pelvises following which methylene blue (0.1%) was infused at a rate of 5 ml/min for 20 minutes. In one pelvis, a 4mA positive pulsed electrical current was applied to the silver wire. Results: In contrast to the control pelvis, the EMDA side macroscopically exhibited dense homogeneous staining; microscopy revealed penetration of methylene blue into the urothelium/lamina propria. Conclusion: In the porcine renal pelvis, application of EMDA increased the penetration of a charged molecule into the urothelium/lamina propria.