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Ureteral stent placement is an acute measure to restore the urinary flow from the kidney to the bladder in cases of acute or chronic obstruction or a functional disturbance of ureteral peristalsis. In cases with chronic obstruction and poor prognosis due to surgical or sometimes patient preference, ureteral stenting may be used as a permanent treatment. With long-dwell time ureteral stenting, the problems of stent encrustation, biofilm formation, and bacterial colonization become important. Excessive stent encrustation to stent blockage and, consequently, pain, fever, renal infection, impairment of renal function and even renal failure. Encrustations of urinary stents are due to the crystallization of soluble minerals in urine, predominantly calcium oxalate salts. The quantification of this process is highly individualized. This process can occur without significant bacterial contamination but facilitates the adherence, persistence and multiplication of bacteria in biofilms. Uropathogenic microorganisms are either introduced into the bladder when a stent is inserted, or they migrate into the bladder along a transurethral catheter over time.Work is underway for new concepts to develop biomaterials with reduced encrustation propensity and biofilm formation. Promising candidates are coated materials with anti-adhesive properties through covalent binding, high hydrophilicity, and good mechanical properties allowing for adequate patient comfort. Taken together, the use of urinary stents or catheters is characterized by three interrelated problems: a tendency for encrustations through the deposition of urinary crystal-forming ions, facilitation of bacterial colonization and persistence despite antibiotic prophylaxis/treatment, and mechanical irritation with resulting reaction of the ureteral tissues. |
