Ureteral stents—weighing up the risks and benefits

Immersed multilayer biodegradable ureteral stent with reformed biodegradation: An in vitro experiment

Objective

The aim of this study was to develop a novel immersed multilayer biodegradable ureteral stent with reformed biodegradation and evaluate it in vitro.

Methods

Poly(glycolic-co-lactic acid) (PGLA), microsphere zein and BaSO4 were employed to produce a multilayer biodegradable stent using immersion technology. Tests of the biodegradable stents and conventional control stents were conducted in human urine in vitro to evaluate the biodegradable properties. The biocompatibility was assessed by the morphology and proliferation of urine-derived cells cultured with extracted media from the biodegradable stent and a latex material positive control.

Results

An immersed multilayer biodegradable stent was successfully produced. It began to degrade in week 2 and was fully degraded by week 4. The mass loss ratio in the first 2 weeks was low (approximately 10.0% at 1 week, 20.0% at 2 weeks) and increased after 3 weeks (approximately 70%) to the end of testing. During the first 2 weeks, the radial compression load performances of the biodegradable stents were better than those of the control stents with statistically significant differences ( p = 0.00, p = 0.01) and the tensile strengths were lower in the biodegradable stents than those in the control stents throughout the experiment. SEM showed that the stents degraded layer by layer from the outer to the inner wall. The influences on the cells of extracted medium from the biodegradable stents were morphologically slight and lower than 10% in relative growth rates.

Conclusions

This preliminary study demonstrates that the immersed multilayer biodegradable ureteral stent has good radial compression and biocompatible performance and can be degraded in vitro within 4 weeks in a moderate manner.

Braided thin-walled biodegradable ureteral stent: preliminary evaluation in a canine model

OBJECTIVES

To evaluate a novel designed degradable ureteral stent.

METHODS

A total of 24 male Beagles, each with bilateral stents implanted (a biodegradable ureteral 4.5-Fr stent and a standard 4-Fr biostable stent) were divided into four groups. Intravenous pyelography, B-mode ultrasonography, and blood and urine tests were carried out before the procedure (0 weeks), and at 1-, 2-, 3- and 4-week intervals. Meanwhile, the mechanical characteristics of stents were tested, and scanning electron microscopy images of the biodegradable braided stents were obtained at different time-points postoperatively. In addition, histopathological changes were compared between the two different stents.

RESULTS

All biodegradable braided stents began degrading at 1 week, and had completely degraded by 4 weeks. Hydronephrosis was equivalent during the first 2 weeks, but less with the biodegradable stents than with the control biostable stents at 3 and 4 weeks. Preoperative and postoperative blood and urine results were similar. The mechanical properties of the biodegradable stents were better than conventional biostable stents. Scanning electron microscopy images obtained at different weekly intervals showed that stents degraded in a predictable fashion. Histological testing of the urinary tract showed that the stent-related tissue reactivity of the two different stents were similar.

CONCLUSIONS

Our novel braided thin-walled biodegradable stents provide temporary renal drainage as good as commercially available biostable stents. They also have good biocompatibility and physical characteristics. Therefore, they might have clinical application.

Mechanisms of Weight Regain following Weight Loss

Obesity is a world-wide pandemic and its incidence is on the rise along with associated comorbidities. Currently, there are few effective therapies to combat obesity. The use of lifestyle modification therapy, namely, improvements in diet and exercise, is preferable over bariatric surgery or pharmacotherapy due to surgical risks and issues with drug efficacy and safety. Although they are initially successful in producing weight loss, such lifestyle intervention strategies are generally unsuccessful in achieving long-term weight maintenance, with the vast majority of obese patients regaining their lost weight during followup. Recently, various compensatory mechanisms have been elucidated by which the body may oppose new weight loss, and this compensation may result in weight regain back to the obese baseline. The present review summarizes the available evidence on these compensatory mechanisms, with a focus on weight loss-induced changes in energy expenditure, neuroendocrine pathways, nutrient metabolism, and gut physiology. These findings have added a major focus to the field of antiobesity research. In addition to investigating pathways that induce weight loss, the present work also focuses on pathways that may instead prevent weight regain. Such strategies will be necessary for improving long-term weight loss maintenance and outcomes for patients who struggle with obesity.