In vivo porcine model for practicing retrograde intrarenal surgery

Harnessing magnetism: evaluation of safety, tolerance and feasibility of magnetic kidney stone retrieval in vivo in porcine models

The primary objective of urolithiasis therapy is complete stone removal and highest stone-clearance rates possible to minimize recurrence. A novel approach that employs a magnetic suspension and a magnetic probe for the passive collection and removal of small residual fragments was developed. This study assessed the feasibility of this system in porcine models. Five female domestic pigs underwent retrograde intrarenal surgery under general anaesthesia to assess the new magnetic system. Pre-analysed human calculi were endoscopically inserted and comminuted using lithotripsy. The magnetic suspension was applied, and the magnetic-stone fragment complex was extracted. After nephrectomy, independent blinded pathologists evaluated all the kidneys. Safety and tolerance assessments revealed no adverse events (i.e. no complications on the Clavien-Dindo scale > 1) or complications associated with treatment. This study revealed superficial urothelial damage in all animals, characterized by desquamation and inflammation, caused primarily by the insertion of access sheaths and laser lithotripsy. Residual magnetic particles were observed in the renal pelvis but did not show signs of toxicity even though this study is limited to the acute treatment. No pathological indicators were observed in the hemogram and urinalysis. Overall, the treatment did not cause any significant pathological changes. Preclinical in vivo evaluation of magnetic extraction of small rest fragments in porcine kidneys presents a promising, atraumatic approach for fragments removal. It demonstrated safety, tolerance, and feasibility that warrants clinical investigation. This method has the potential to increase stone-clearance rates with shorter extraction times, offering a possibility for addressing the challenge of urolithiasis in clinical practice.

Advances in experimental bladder models: bridging the gap between in vitro and in vivo approaches for investigating urinary tract infections

Urinary tract infections (UTIs) pose a substantial burden on global healthcare systems. When unraveling the complex pathophysiology of UTIs, bladder models are used to understand complex and multifaceted interactions between different components within the system. This review aimed to bridge the gap between in vitro and in vivo experimental bladder models towards UTI research. We reviewed clinical, animal, and analytical studies and patents from 1959 to the end of 2023. Both in vivo and in vitro models offer unique benefits and drawbacks in understanding UTIs. In vitro models provide controlled environments for studying specific aspects of UTI biology and testing potential treatments, while in vivo models offer insights into how UTIs manifest and progress within living organisms. Thus, both types of models are leading to the development of more effective diagnostic tools and therapeutic interventions against UTIs. Moreover, advanced methodologies involving three-dimensional bladder organoids have also been used to study bladder biology, model bladder-related disorders, and explore new treatments for bladder cancers, UTIs, and urinary incontinence. Narrowing the distance between fundamental scientific research and practical medical applications, these pioneering models hold the key to unlocking new avenues for the development of personalized diagnostics, precision medicine, and ultimately, the alleviation of UTI-related morbidity worldwide.

Establishment of an artificial urine model in vitro and rat or pig model in vivo to evaluate urinary crystal adherence

The current study aimed to establish an experimental model in vitro and in vivo of urinary crystal deposition on the surface of ureteral stents, to evaluate the ability to prevent crystal adhesion. Non-treated ureteral stents were placed in artificial urine under various conditions in vitro. In vivo, ethylene glycol and hydroxyproline were administered orally to rats and pigs, and urinary crystals and urinary Ca were investigated by Inductively Coupled Plasma-Optical Emission Spectrometer. in vitro, during the 3- and 4-week immersion periods, more crystals adhered to the ureteral stent in artificial urine model 1 than the other artificial urine models (p < 0.01). Comparing the presence or absence of urea in the composition of the artificial urine, the artificial urine without urea showed less variability in pH change and more crystal adhesion (p < 0.05). Starting the experiment at pH 6.3 resulted in the highest amount of crystal adhesion to the ureteral stent (p < 0.05). In vivo, urinary crystals and urinary Ca increased in rat and pig experimental models. This experimental model in vitro and in vivo can be used to evaluate the ability to prevent crystal adhesion and deposition in the development of new ureteral stents to reduce ureteral stent-related side effects in patients.

Construction of a novel rabbit model of ureteral calculi implanted with flowable resin

BACKGROUND

The purpose of this study was to characterize the pathophysiological changes of hydronephrosis caused by ureteral calculi obstruction in a new rabbit ureteral calculi model by implanting flowable resin.

METHODS

Forty New Zealand rabbits were randomly divided into two groups: the calculi group and the sham control group. In the calculi group (n = 20), rabbits were operated at left lower abdomen and the left ureter was exposed. Then flowable resin (flowable restorative dental materials) was injected into the left ureter using a 0.45 mm diameter intravenous infusion needle. Then light-cured for 40 s by means of a dental curing light to form calculi. In the sham control group, normal saline was injected into the ureter. Rabbits underwent X-ray and routine blood and urine tests preoperatively, as well as X-ray, CT, dissection, HE staining and routine blood and urine tests on 1, 3, 5 and 7 days postoperatively. Stone formation was assessed by X-ray and unenhanced CT scan after surgery. The pathophysiological changes were evaluated through dissection, HE staining and routine blood and urine tests.

RESULTS

Ureteral calculi models were successfully constructed in 17 rabbits. In calculi group, high-density shadows were observed in the left lower abdomen on postoperative day 1st, 3rd, 5th and 7th by X-ray and CT scan. Dissection found obstruction formation of the left ureters, dilatation of the renal pelvis and upper ureter during 7 days after surgery. The renal long-diameters of the left ureters increased only on the 1st postoperative day. HE staining found ureteral and kidney damage after surgery. In calculi group and sham group,the serum creatinine, urea nitrogen, white blood cells and urine red blood cells were raised at day 1 after surgery. However, the indicators returned to normal at day 3, 5, and 7.

CONCLUSIONS

This is a stable, less complicated operation and cost-effective ureteral calculi model by implanting flowable resin. And this novel model may allow us to further understand the pathophysiology changes caused by ureteral calculi obstruction.

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.

Viability and biocompatibility of an adhesive system for intrarenal embedding and endoscopic removal of small residual fragments in minimally-invasive stone treatment in an in vivo pig model

PURPOSE

To evaluate the viability and biocompatibility of a novel, patented bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy. Complete stone clearance via active removal of residual fragments (RF) after intracorporeal laser lithotripsy may be time-consuming and fail in many cases. Therefore, the novel adhesive has been developed and evaluated for the first time in an in vivo pig model in the present work.

METHODS

Four female domestic pigs underwent flexible ureteroscopy (RIRS) or percutaneous nephrolithotomy (PNL) under general anesthesia (8 kidneys, 4 × RIRS, 4 × PNL) evaluating the bioadhesive system.

INTERVENTIONS

RIRS without adhesive system (sham procedure, kidney I); 3 × RIRS using the bioadhesive system (kidneys II-IV); and 4 × PNL using the bioadhesive system (V-VIII). We endoscopically inserted standardized human stone probes followed by comminution using Ho:YAG lithotripsy. The bioadhesive (kidney II-VIII) was then applied and the adhesive-stone fragment complex extracted. After nephrectomy, all kidneys were evaluated by two independent, blinded pathologists. Endpoints were the procedure's safety and adhesive system's biocompatibility.

RESULTS

We observed no substantial toxic effects. We were able to embed and remove 80-90% of fragments. However, because of the pig's hampering pyelocaliceal anatomy, a quantified, proportional assessment of the embedded fragments was compromised.

CONCLUSIONS

For the first time, we demonstrated the proven feasibility and safety of this novel bioadhesive system for embedding and endoscopically removing small RF in conjunction with a lack of organ toxicity in vivo.

Modular training for percutaneous nephrolithotripsy: The safe way to go

Objectives should be describe a modular training scheme (MTS) which aims to provide training in percutaneous nephrolithotripsy (PCNL) and ensure the safety of the patients.

Subjects and methods

Two trainees with no experience in PCNL attended the MTS under the supervision of an experienced mentor. The MTS included five modules, comprising an initial animal laboratory course (using pigs), to acquire basic skills (Module 1), and Modules 2–5 included making the puncture, tract dilatation, single-stone and large-stone management in clinical cases, respectively. Each participant progressed from one module to the next under constant mentoring and evaluation by the mentor. When the trainees completed the MTS they proceeded to perform 60 PCNL procedures independently while the mentor performed 25 for comparison purposes. A global rating scale was used for the objective evaluation of the trainees. Peri-operative variables were recorded and statistically compared as appropriate. Statistical significance was defined as P < 0.05.

Results

One pig and 16 patients, and two pigs and 22 patients, were necessary to complete the MTS by each subject. There were no significant differences among the characteristics of the independently performed operations. The duration of surgery and fluoroscopy achieved a plateau similar to those of the mentor after ≈ 30 patients. The decrease in haemoglobin level, stone-free and complication rates in the patients were similar among the two trainees and the mentor. The complication rate of the trainees and the mentor never exceeded 13.3%.

Conclusion

The MTS successfully combined animal and stepwise clinical training based on a standardised technique and objective evaluation.

Catheterization of the urethra in female pigs

Female pigs are commonly utilized as an animal model for biomedical research and require urethral catheterization. Sixteen pigs were anaesthetized for research purposes and required the placement of a urethral catheter. Post-mortem examination of the vaginas revealed the urethral opening to be consistently halfway from the mucocutaneous junction of the vulva to the cervix. A shallow diverticulum was also observed on the ventral floor of the urethral opening. To optimize conditions for success the pig should be carefully positioned supine, a vaginal speculum and light source should be used, the pig should be adequately anaesthetized, and the anatomy of the vagina should be reviewed.

Novel Transparent Urinary Tract Simulator Improves Teaching of Urological Operation Skills at a Single Institution

OBJECTIVE

This randomized controlled study compared a novel transparent urinary tract simulator with the traditional opaque urinary tract simulator as an aid for efficiently teaching urological surgical procedures.

METHODS

Senior medical students were tested on their understanding of urological theory before and after lectures concerning urinary system disease. The students received operative training using the transparent urinary tract simulator (experimental group, n = 80) or the J3311 opaque plastic urinary tract simulator (control, n = 80), specifically in catheterization and retrograde double-J stent implantation. The operative training was followed by a skills test and student satisfaction survey.

RESULTS

The test scores for theory were similar between the two groups, before and after training. Students in the experimental group performed significantly better than those in the control group on the procedural skills test, and also had significantly better self-directed learning skills, analytical skills, and greater motivation to learn.

CONCLUSION

During the initial step of training, the novel transparent urinary tract simulator significantly improved the efficiency of teaching urological procedural skills compared with the traditional opaque device.