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Once again, a newsletter from our ureteral stents series. I have chosen from the most recent scientific literature three very interesting papers with very different profiles.

The first one, from my hospital colleagues, discusses metallic stents with one of the longest clinical series and confirms that metallic stents have clear indications as a treatment option for complex ureteral strictures in fragile patients with low life expectancy. As always, the benefit/risk balance should determine clinical decisions.

The second paper is a systematic review and meta-analysis related to magnetic ureteral stents, where parameters such as efficacy of stent removal, pain during removal, removal time, healthcare costs, complications, and patient satisfaction are compared with conventional ureteral stents.

Finally, I cannot resist including an experimental manuscript on biodegradable ureteral stents. In this case, the researchers assess a new design of a biodegradable stent with a spiral conformation, developed using 3D printing, which represents the near future of personalized stents.

I hope you enjoy this selection.

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In this paper, the authors perform an insightful retrospective study over 25 years on the treatment of ureteral strictures with metallic self-expandable ureteral stents. Mainly, metallic stents are an alternative for patients who are refractory to endourological treatment or those who are not suitable for ureteral reconstructive surgery. The authors present long-term results and complications of metallic ureteral stents in a tertiary institution. Often, in these patients, the first resort is to drain the urinary tract by means of a PCN or a ureteral stent. However, it should be remembered that double-J ureteral stents have a failure rate of up to 60% due to extrinsic compressions, mainly of oncological origin.

The authors enrolled 56 patients in whom they implanted 69 metallic ureteral stents. Patients were selected for ureteral stenting, taking into account their frailty, previous surgeries, and life expectancy. The median follow-up was 36 months, and the median age was 61 years. Following stent placement, the median serum creatinine decreased from 1.8 mg/dL to 1.4 mg/dL in the first month. Renal function parameters improved in 48.3% of patients. The main acute complications reported after stent placement were urinary tract infection in 3.4% of patients and hematuria in 5.2% of cases.

Unfortunately, as is common with the placement of metallic stents, 35% of patients showed a decrease in ureteral patency due to stent incrustation or obstructive urothelial hyperplasia. The authors managed this appropriately with coaxial double-J stenting in 24% of patients and, in up to 10%, with drainage by percutaneous nephrostomy. At 12 months, 62.4% of stents were functioning, and 47.7% of ureteral stents remained permeable at 60 months.

A multitude of metallic ureteral stent designs—Memokath, Uventa, Allium—have been developed with successful results in selected patients. The authors conclude quite correctly that metallic ureteral stents are an alternative to PCN or double-J stenting in fragile patients with both benign and malignant ureteral strictures, eliminating the need for frequent PCN/stent replacement and preserving quality of life. They have an acceptable mean survival time, and associated complications are infrequent.

For these reasons, ureteral stents should be considered a treatment option for complex ureteral strictures in fragile patients with low life expectancy. The selection of patients who can benefit from this type of stent is the most important factor. Therefore, metallic stents should be part of the endourological armamentarium despite their well-known adverse effects. As always, the benefit/risk balance should determine clinical decisions.

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We are going to discuss an interesting Systematic Review and Meta-Analysis of a double-J ureteral stent design, known as ‘magnetic ureteral stents’. Magnetic ureteral stents are designed with a magnetic tip that allows for non-invasive retrieval using a handheld magnetic device. This design innovation eliminates the need for cystoscopy in many cases, enabling removal in outpatient settings, which significantly reduces the procedural burden on urology departments. Beyond the efficacy of stent removal, magnetic stents have demonstrated multiple patient benefits in clinical studies, such as the reduction of pain during removal, shorter removal time, lower overall healthcare costs, and high patient satisfaction rates.

The authors perform a systematic review and meta-analysis aimed at assessing the use of magnetic ureteral stents, focusing on pain during stent removal, procedural efficacy, patient satisfaction, complication rates and cost-effectiveness, and compare these endpoints with traditional stents.

The clinical practice focus of this study can be summarised as follows: A meta-analysis of USSQ scoresshowed a significant reduction in stent-related symptoms for patients with magnetic stents compared to conventional stents. Particularly in domains such as: pain; urinary symptoms; impact on work performance.

About pain during stent removal; The pooled mean pain score was 2.3, which was significantly lower compared to 5.9 for conventional stent removal. Stent removal time, showed that the average procedure time for magnetic stent removal was 1-2 minutes, significantly shorter than 12-15 minutes for conventional stent removal. Complications, complication rate was 7.2% for magnetic stents, compared to 8.6% for conventional stents. The difference was not statistically significant. Failure of Magnetic Stent Removal, three studies reported 2% failure rates for magnetic stent removal requiring cystoscopic intervention. Cost-Effectiveness, a meta-analysis of cost data revealed an average 25% reduction in procedural costs  for magnetic stent removal compared to conventional cystoscopy-based removal. This reduction was attributed to shorter procedure times and the elimination of the need for an operating room in most cases.

The authors conclude that magnetic ureteric stents represent a promising advancement, offering a safer, more comfortable, and cost-effective alternative to conventional stent removal. In my opinion, probably in renal transplant patients, where the manipulation should be kept to a very low level, avoiding cystoscopy may reduce the rate of infection and in this scenario it is very important. We are still waiting for the appearance of biodegradable stents.

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To conclude this newsletter, a very interesting scientific manuscript on the printing of 3D biodegradable ureteral stents, the hopefully not so far off future. The fact is that with the extraordinary development of 3D printing in recent years, the manufacture of ureteral stents with biodegradable polymers should benefit from the ease of manufacture and possibly also the cost of fabrication.

This study shows experimentation of a biodegradable ureteral stent made of Poly (L-lactide-co-ε-caprolactone) with known biocompatible properties, with excellent elasticity and biodegradable, and have been approved by the FDA, which are promising candidate materials for bioprinting. They carry out studies in artificial urine to assess the biodegradation of the stent and they also carry out a study in a murine animal model. Honestly, the murine (rat) model study does not seem to me to be very adequate and provides little information related to the benefits of the stent and its application in patients. The researchers place a fragment of the stent subcutaneously to assess its systemic effects. But this is an unrealistic scenario, and extracting information related to subcutaneous implantation from future upper urinary tract application is complicated. We lose information on the degradation rate, since the selected polymers degrade mainly by hydrolysis and this will be different in a urinary environment, much faster, and eliminates a very important factor such as ureteral peristalsis, the effect of asymptomatic bacteriuria itself on the stent, and obviously we lose information on possible complications (migration, etc.) only information on biocompatibility can be obtained, which is already assured by using materials approved by the FDA for use in humans.

However, this study does provide a wonderful assessment of the mechanical properties of the stent, which is a biodegradable stent, so it will degrade from the first moment of its implantation. The authors solve this problem in a very interesting way by developing their stent with a spiral structure fabricated by 3D printing and an architecture that allows maintaining the scaffold properties of the stent in a very adequate way. In addition, the stent has a silver ion coating that is already well known to provide antibacterial properties, as demonstrated in this laboratory study of this stent. The novel silver-modified, collagen-coated 3D-printed ureteral stent demonstrates enhanced mechanical strength, antimicrobial properties, biodegradability, and biocompatibility. This innovative design provides a robust theoretical framework for addressing clinical challenges associated with ureteral stents, including bacterial infections linked to stent implantation.

Another study that brings us closer to the long-awaited biodegradable ureteral stents.