Effects of Alpha-Blockade on Ureteral Peristalsis and Intrapelvic Pressure in an In Vivo Stented Porcine Model

Urinary Stent Development and Evaluation Models: In Vitro, Ex Vivo and In Vivo-A European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS) Initiative

Background: When trying to modify urinary stents, certain pre-clinical steps have to be followed before clinical evaluation in humans. Usually, the process starts as an in silico assessment. The urinary tract is a highly complex, dynamic and variable environment, which makes a computer simulation closely reflecting physiological conditions extremely challenging. Therefore, the pre-clinical evaluation needs to go through further steps of in vitro, ex vivo and in vivo assessments. Methods and materials: Within the European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS), the authors summarized and evaluated stent assessment models in silico, in vitro, ex vivo and in vivo. The topic and relevant sub-topics were researched in a systematic literature search in Embase, Scope, Web of Science and PubMed. Clinicaltrials.gov was consulted for ongoing trials. Articles were selected systematically according to guidelines with non-relevant, non-complete, and non-English or Spanish language articles excluded. Results: In the first part of this paper, we critically evaluate in vitro stent assessment models used over the last five decades, outlining briefly their strengths and weaknesses. In the second part, we provide a step-by-step guide on what to consider when setting up an ex vivo model for stent evaluation on the example of a biodegradable stent. Lastly, the third part lists and discusses the pros and cons of available animal models for urinary stent evaluation, this being the final step before human trials. Conclusions: We hope that this overview can provide a practical guide and a critical discussion of the experimental pre-clinical evaluation steps needed, which will help interested readers in choosing the right methodology from the start of a stent evaluation process once an in silico assessment has been completed. Only a transparent multidisciplinary approach using the correct methodology will lead to a successful clinical implementation of any new or modified stent.

Pigtail Suture Stents Significantly Reduce Stent-related Symptoms Compared to Conventional Double J Stents: A Prospective Randomized Trial

Background

Double J (DJ) ureteral stents are commonly inserted after ureteroscopy (URS) procedures for stone treatment. However, stent-related symptoms are still a major issue.

Objective

To determine whether a commercially available pigtail suture stent (PSS) can reduce stent-related symptoms compared to a conventional DJ stent after uncomplicated URS.

Design setting and participants

We designed a randomized, single-blind, parallel-group trial from January to November 2020. The inclusion criteria were stone-free URS without intraprocedural complications. Patients with distal ureteral stones were excluded.

Intervention

Insertion of a PSS or DJ stent after URS.

Outcome measurements and statistical analysis

The primary endpoint was the Urinary Symptom Index score on the Ureteral Stent Symptoms Questionnaire (USSQ) 2 wk after URS. Secondary endpoints were USSQ domain scores and responses to individual USSQ questions at 2 d and 2 wk after surgery.

Results and limitations

A total of 78 patients were randomized and treated according to protocol. The Urinary Symptom Index score (p = 0.004), overall Visual Analogue Scale (VAS) score (p = 0.022), and the percentage of patients complaining of pain (63.9% vs 86.1%, p = 0.029) were significantly in favor of PSS at both 2 d and 2 wk after URS. At 2 d, the VAS score among patients with pain (p = 0.025) and the General Health Index score (p = 0.036) were significantly better in the PSS group. No severe complications occurred in either group. Study limitations are the exclusion of patients with distal ureteral stones and the limited sample size.

Conclusions

PSS significantly reduced stent-related symptoms after URS, in particular urinary symptoms and pain, compared to conventional DJ stents, and showed a good safety profile.

Patient summary

Stents are hollow tubes placed in the passage between the kidney and the bladder (ureter). The standard stent has two coiled ends (double J stent) to keep it in place in both the kidney and the bladder. We tested a commercial stent with two strings at the bladder end (pigtail suture stent) after procedures to remove stones from the upper urinary tract and found that it caused less stent-related symptoms compared to a double J stent.

This trial is registered at Clinicaltrials.gov as NCT03344120.

17β-estradiol and ureteral contractility: A role for the G protein-coupled estrogen receptor

The aim of this study was to investigate the unknown effects of 17β-estradiol (E2) on ureteral contractility and the receptor and mechanisms involved. By utilising isolated porcine distal ureteral strips, we observed that E2 (30-300 μM) and a G protein-coupled estrogen receptor specific agonist G-1 (30 μM) both increased the frequency of phasic contractions of the ureter (P<0.05). E2 also decreased the maximum amplitude of these contractions (P<0.05). The G protein-coupled estrogen receptor specific antagonist G-36 (10 μM) reversed E2 enhancement effects on frequency, but did not alter its effects on maximum amplitude of contractile responses. Additionally, it was observed that the effects of E2 were unaltered by removing the urothelium, inhibiting nitric oxide and prostaglandin production or preventing neuronal conduction. In the presence of a potassium channel blocker, 4-aminopyridine (10 μM), the effects of E2 on frequency were prevented. This finding suggests that G protein-coupled estrogen receptor mediates the increase in frequency of ureteral phasic contractions induced by E2 via activation of potassium channels, while E2 alters the amplitude of these contractions through an unknown mechanism.

In Vivo Evaluation of a Novel Pigtail Suture Stent

OBJECTIVE

To compare pressure, dilation, and histology in a porcine model after stenting with a pigtail suture stent (PSS)-where the ureteral and bladder component consists of a suture and a double J (DJ) stent.

METHODS

Twelve pigs were studied with a PSS (4.8F/MiniJFil®) and DJ stent (4.8F/RocaJJ Soft) inserted in both sides, except in one where the DJ was not placed to serve as control. Intrapelvic pressure (IPP) and ureteral pressures were recorded. Five pigs were stented for 7 days, and the next 7 for 13-15 days, where a retrograde study was performed after stent removal. Ureteral histology in 4 and 3 pigs stented for 7- and 13-15 days, respectively, were assessed in a blinded manner.

RESULTS

In total, 11 renal units were stented with PSS and DJ, respectively. There was a rise in IPP and ureteral pressure after stenting. There were no significant differences in post-stenting pressures between DJ and PSS systems. Ureteral dilation occurred in 100% of DJ and 83% of PSS units. PSS suture migration occurred in 3 of 11. Gross edema at the ureteral orifice was greater with the DJ compared to the PSS (82% vs 18%; p = .003). Histology demonstrated greater inflammation at the ureteral orifice in the DJ group (2.3 vs 1; p = .016) when stented for 13-15 days.

CONCLUSION

There was no difference in IPP after stenting with a PSS compared to a DJ stent. When stented for 13-15 days, the PSS resulted in ureteral dilation, but with less edema and inflammation at the ureteral orifice.

Preoperative Alpha-Blockers for Ureteroscopy for Ureteral Stones: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Introduction: Preoperative alpha-blockers have been proposed to improve intraoperative outcomes and patient stone-free status after ureteroscopy for ureteral stones. Materials and Methods: We searched six databases, including Medline, Embase, and Web of Science, for randomized controlled trials (RCTs) evaluating alpha-blocker use before planned ureteroscopy for the management of ureteral calculi. Meta-analysis was performed using DerSimonian and Laird method with inverse variance weighting. Quality of evidence was summarized using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework. Results: Of 3338 records, 26 were screened as full text and 12 RCTs were included totaling 1352 patients. Meta-analysis demonstrated a 61% risk reduction in need for intraoperative ureteral dilatation in patients administered preoperative alpha-blockers (relative risk [RR]: 0.39 [95% confidence interval, CI: 0.31-0.48], p < 0.00001), as well as increased stone-free status for patients at 4 weeks postoperatively (RR: 1.17 [95% CI: 1.08-1.26], p < 0.0001), and at final follow-up (RR: 1.18 [95% CI: 1.11-1.24], p < 0.00001; median final follow-up 4 weeks [range: 2-8 weeks]). Urologists were more likely to reach the stone with the ureteroscope in patients administered alpha-blockers (RR: 1.16 [95% CI: 1.10-1.23], p < 0.00001). A statistically significant reduction in operative time (mean difference [MD]: -6.05 [95% CI: -10.17 to -1.93] minutes, p = 0.004) and length of hospital stay (weighted MD: -0.34 [95% CI: -0.55 to -0.13] days, p = 0.001) was also demonstrated. Main reported side effects of treatments were abnormal ejaculation, postural hypotension, and dizziness. Outcomes were robust to sensitivity analyses. Results were rated moderate quality evidence using the GRADE framework. Conclusions: Among patients scheduled for semirigid ureteroscopy of ureteral stones, use of preoperative alpha-blockers demonstrated a significant reduction in the need for ureteral orifice dilation and an increase in patient stone-free status at follow-up, and facilitates higher rate of ureteroscopic access to stones, although reducing operative time. An adequately powered trial is needed to definitively address the safety and efficacy of preoperative alpha-blockers for ureteroscopy of ureteral stones.

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

PURPOSE

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).

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.