Innovation and new technology in ureteral stents

Ureteral stent insertion is a procedure performed extensively by all urologists. Nevertheless, stent-related symptoms and stent encrustation are still common complications pushing the innovation and development of novel ureteral stents. Developments are focussing on three significant aspects: material, design, and removal technique. Various materials including silicone, polymers, and metals are frequently utilized, with or without an additional coating. The use of biodegradable materials is looking promising but these is a lack of proven clinical trials in association with this in humans. The new designs focus on the reduction of stent-related symptoms through the modification of the bladder end. The new stent removal techniques with extraction strings or novel magnetic end may exclude subsequent cystoscopic procedures. Finally, utilization of a ureteral stent tracker application helps in reminding both physicians and patients to remove the stent at the appropriate time.

Stent encrustation or fragmentation? A case report of post stent removal encrustation in postpartum woman and literature review

Background Ureteral stents are commonly used in the field of urology to relieve ureteral obstruction. However, complications relating to ureteral stent use, such as encrustation continue to occur, especially with prolonged indwell time. Case presentation Here we present a 37-year-old postpartum woman with a foreign body in her bladder after removing a ureteral stent 1 month before. She insisted that the foreign body was the fragment of stent and asked for medical malpractice indemnity payments while the surgeon of her insisted that the stent was intact during the procedure. Finally, the foreign body was confirmed as an encrustation by cystoscopy and the patient received 10,000 yuan ($ 1500) as indemnity payments after encrustation removal. Conclusion In the absence of guidelines, stent indwelling time vary with centers’ habits, stent materials and patient’s education. Early detection of stent encrustation and timely removal of the encrusted stent are still the best way to avoid stent retention. Violent stent removal is of danger and not recommended in any case.

Developments in Ureteral Stent Technology

Ureteral stents have been utilized for decades in maintaining ureteral patency, most commonly after ureteroscopy in the treatment of urolithiasis. Since their initial development, ureteral stents have had many technological advances that have allowed for better patient outcomes with improvements in comfort, durability, patency, encrustation resistance, biocompatibility, ease of insertion, migration, and biofilm development. Several new ureteral stents enter the market every year, each with their own touted benefits. It is essential to understand the different advantages for each ureteral stent to provide the best available care to patients when possible. The purpose of this review is to give a brief history of ureteral stent development and summarize the recent developments in ureteral stent designs. We aim to review the data supporting the clinical advantages of the latest ureteral stents available for use by urologists.

Novel method to decrease the exposure time of the extraction string of the ureteral stent and its efficiency and safety verification in the clinic

Ureteral stent removal by an extraction string is advantageous. However, the increased risk of complications attributed to the continuous exposure of the string outside the urethra must be managed. This paper introduces a method to decrease the exposure time, and conducts a retrospective study to verify its efficiency and safety. A total of 231 male patients undergoing routine ureteroscopy (URS) were included, and all of them accepted indwelling ureteral stents with strings. Among them, 123 patients (Normal-S group) underwent the normal method to determine the length of string (Lstring), which was shortened to 4 cm (cm) past the urethral meatus; 108 patients (Novel-S group) underwent the novel method (Lstring = Lurethra + 2 cm), the length of urethra (Lurethra) was measured during ureteroscopy by ureteroscope body. The demographic characteristics, stent indwelling and removal-related variables, complications, and medical costs in each group were recorded. There was no significant difference in demographic characteristics, the rate of UTI, the operative duration of URS, or the VAS pain scores for stent removal between the 2 groups. For the Novel-S group, the stent dwelling time was longer, the self-rated discomfort and symptom, the stent dislodgement rate, the numbers of clinic or emergency visits and the overall medical cost post operation was lower in comparison with the Normal-S group, while the rate of removal of stents by hand was lower, the time for removing ureteral stents was longer. This novel method improved stenting comfort, avoided ureteral stent dislodgement, decreased complications, and lowered medical costs, it was safe and reliable and merits widespread application.

Effect of Potassium Sodium Hydrogen Citrate Granule on The Wall

Objective: To observe the effect of potassium sodium hydrogen citrate Granule on the wall stone shell of preset ureteral stent before ureteroscopy. Methods: 263 cases of renal calculi treated in our hospital from January 2019 to June 2021 who needed ureteroscopy and successfully preset ureteral stent were investigated retrospectively. 129 cases of patients who took oral potassium sodium citrate granules 10g a day from preset ureteral stent and maintained pH between 7.6 ~ 8.0 until before ureteroscopy were classified into the experimental group, 134 patients without oral administration of any drugs were classified as the control group. The patients in the experimental group took Potassium Sodium Citrate Granules orally. The daily dose was 4 standard spoons, 1 spoonful in the morning, 1 spoonful at noon and 2 spoonfuls in the evening. Both groups of patients returned to the hospital for ureteroscopic lithotripsy after 3 weeks according to the doctor’s advice. After pulling out the ureteral stent tube during the operation, the two doctors observed whether there was wall attached stone shell on the surface of the ureteral stent tube and the thickness of the stone shell, and recorded it in a special notebook after unified opinions. Finally, weigh the weight of ureteral stent and completely scrape off the stone shell to obtain the weight of stone shell. Results: In the experimental group, 129 ureteral stents were pulled out, of which 7 showed thin stone shells and 4 showed thicker stone shells (the thickest part ≥ 1mm). The stone shell formation rate was 8.53%, and the average stone shell weight was 0.8521 ± 0.1952 G. In the control group, 134 ureteral stents were pulled out, including 21 thin stone shells and 9 thick stone shells. The stone shell formation rate was 22.39%, and the average stone shell weight was 1.7823 ± 0.1802 G. The ureteral stent was pulled out at one time in both groups. After oral administration of youlaite, there were significant differences in stone shell formation rate, stone shell thickness and stone shell weight between the two groups (P < 0.05). Conclusion: Potassium sodium hydrogen citrate granules can be used as an economic, effective and safe drug to reduce the formation of stone shell attached to ureteral stent and slow down the progress of stone shell thickness, which is worthy of clinical promotion.

Quantitative Evaluation of Encrustations in Double-J Ureteral Stents With Micro-computed Tomography and Semantic Segmentation

Accurate evaluations of stent encrustation patterns, such as volume distribution, from different patient groups are valuable for clinical management and the development of better stents. This study compared stent encrustation patterns from stone and kidney transplant patients. Twenty-three double-J ureteral stents were collected at a single center from patients with stone disease or underwent kidney transplantation. Encrustations on stent samples were quantified by means of micro‑computed tomography and semantic segmentation using Convolutional Neural Network models. Luminal encrustation volume per stent unit was derived to represent encrustation level, which did not differ between patient groups in the first six weeks. However, stone patients showed higher encrustation levels over prolonged indwelling times (p = 0.036). Along the stent shaft body, the stone group showed higher encrustation levels near the ureteropelvic junction compared to the ureterovesical junction (p = 0.013), whereas the transplant group showed no such difference. Possible explanations were discussed regarding vesicoureteral refluxes. In both patient groups, stent pigtails were more susceptible to encrustations, and no difference between renal and bladder pigtail was identified. Our results suggest that excessively long stents with superfluous pigtails should be avoided.

Numerical Study of Fully Coupled Fluid-Structure Interaction of Stented Ureter by Varying the Stent Side-Holes

Ureteral stents are a measure used for many medical issues involving urology, such as kidney stones or kidney transplants. The purpose of applying stents is to help relieve the urine flow while the ureter is either blocked or trying to close itself, which creates blockages. These ureteral stents, while necessary, cause pain and discomfort to patients due to them being a solid that moves around inside the patients’ body. The ureter normally moves urine to the bladder through peristaltic forces. Due to the ureter being a hyperelastic material, these peristaltic forces cause the ureter to deform easily, making it necessary for the stent to properly move the urine that flows through it for the patient not to face further medical complications. In this study, we seek to find a relation between the amount of stent side holes and the overall flow rate inside the stent with the ureter contracting due to peristalsis. A fully coupled fluid-structure interaction (FSI) model is developed to visualize how the ureter deforms due to peristalsis and the subsequent effect on the urine flow due to the ureter’s deformation. Numerical simulations using COMSOL Multiphysics, a commercial finite-element based solver, were used to study the fluid-structure interaction, and determine whether the stent performs more properly as the amount of stent side holes increases. The results showed that the stent model with a 10 mm distance between side hole pairs provided the highest outlet flow rate, which indicates a proper stent design that allows for maximized urine discharge. We hope this study can help improve the stent design in kidney transplant procedures to further ease the inconvenience on the patients.