Advances in ureteral stents

Abstract

Ureteral stents are commonly used in urology. Every urologist is familiar with the problems that are associated with stents including infection, encrustation, and bothersome symptoms. These problems limit and affect the use of ureteral stents which are necessary, even in light of the problems they can cause. New designs such as a helically cut ureteral stent which is designed to stretch and conform to the ureter is designed to improve comfort. Drug-eluting designs with an antimicrobial (triclosan) are designed to reduce bacterial adherence to ureteral stents. Chlorhexidine, an antiseptic, has been incorporated into a stent and held in place by a slow release varnish to prevent biofilm formation. Combinations of antibiotics coated directly on the stent and administered systemically have been shown to reduce stent colonization both in vitro and in vivo. Gel-based ureteral stents were also showed to reduce bacterial infection and colonization. Bioabsorbable materials have also been designed to reduce infection, symptoms and prevent the forgotten stent syndrome. Newer designs including stents based on guidewire technology, gels, and a combination of self-expanding wire stents with polymer films are reviewed. There is hope on the horizon that new stents will be able to effectively tackle problems that are often seen with ureteral stents.

Keywords: Ureteral stent; biofilm; biomaterials; nephrolithiasis; polymer.

Figure 1

Percuflex Helical^TM Ureteral Stent (Boston Scientific Corporation, Natick, MA). This stent is based on the Percuflex^TM material and is cut in a spiral fashion along the straight portion of the stent. The stent is designed to conform readily to the shape of the ureter in an attempt to improve patient comfort.

Figure 2

MicroStent^TM (Percutaneous Systems Inc., Palo Alta, CA). Based on a guidewire delivery system and the anti-retropulsion device made by the company (Accordion^TM), it is designed to be inserted directly into the ureter beyond the stone and the triangular film “accordions” together to hold it in place. The holes in the film line up to promote passage of urine through the film.

Figure 3

X-ray of MicroStent^TM in the distal ureter.

Figure 4

Uriprene^TM degradable ureteral stent (Poly-Med Inc., Anderson, SC). This stent is designed to degrade over time while providing structural integrity to promote urinary drainage from the kidney.