Current status of metal stents for managing malignant ureteric obstruction

Abstract

Obstruction of the ureters caused by extrinsic compression from a primary tumour or retroperitoneal lymph node masses is not unusual in the course of advanced pelvic malignancies. Most of the cases are of gynaecological or gastrointestinal origin, and the situation can be aggravated by peri‐ureteric fibrosis, a long‐term adverse event of previous chemotherapy or radiotherapy. Undoubtedly upper urinary tract decompression and maintenance of ureteric patency, even as a palliative measure, is important in managing these patients. Options for upper tract decompression include percutaneous nephrostomy, retrograde stenting and open urinary diversion. Plastic stents have long been used for managing malignant ureteric obstruction, but their overall success remains limited. Plastic stents often fail to be placed correctly, require regular exchange, and are faced with a high incidence of encrustation and migration. For these reasons plastic stents have been unsuccessful for long‐term maintenance of ureteric patency. To overcome these limitations metal stents were introduced and recently developed in an effort to ensure better long‐term patency of the obstructed ureter, fewer hospital admissions for stent change and better overall quality of life. In the present review the clinical applications of different types of metal stents are discussed, with a specific focus on the latest advances and the future options for managing malignant ureteric obstruction.

New Metallic Ureteral Stents: Improved Tensile Strength and Resistance to Extrinsic Compression

“…This is primarily achieved by reducing the number of hospitalizations and exposure to anesthesia along with the risk of complications that can occur with a stent exchange. 11 While metallic stents have shown patency rates greater than the 3 to 6 months seen with polymer stents, patients still need to be followed closely for evidence of obstruction, encrustation, infection, or painful stent symptoms because there is no well-established optimal dwelling time for these devices. [11][12][13] Cystoscopy can be a tool for monitoring stent encrustation, because the visual appearance of encrustation at the distal end of a stent may correlate with upper stent encrustation.…”

Renal and urologic problems

“…Stent failure from encrustation and obstruction is a problem in up to 58% of patients [10][11][12], and conventional polymeric stents require 3-4 monthly changes [13,14]. Different strategies have been developed to minimize stent failure including inserting two parallel stents and the use of longer-lasting compression-resistant metallic stents.…”

Biomaterials in Urology - Beyond Drug Eluting and Degradable - A Rational Approach to Ureteral Stent Design

“…Metal ureteral stents were introduced by Pauer in 1992 (Pauer and Lugmayr 1992) and have been utilized in the treatment of malignant ureteric obstruction (Kulkarni and Bellamy 2001;Liatsikos, Karnabatidis et al 2009;Masood, Papatsoris et al 2010;Papatsoris and Buchholz 2010;Sountoulides, Kaplan et al 2010), ureteral strictures (Daskalopoulos, Hatzidakis et al 2001;Papatsoris and Buchholz 2010), and ureteropelvic junction obstruction Masood, Papatsoris et al 2010;Benson, Taylor et al 2011). Current problems associated with metallic stents include biofilm formation, infection, migration, and tissue hyperplasia leading to luminal obstruction Wah, Irving et al 2007;Liatsikos, Karnabatidis et al 2009;Sountoulides, Kaplan et al 2010).…”

“…Current problems associated with metallic stents include biofilm formation, infection, migration, and tissue hyperplasia leading to luminal obstruction Wah, Irving et al 2007;Liatsikos, Karnabatidis et al 2009;Sountoulides, Kaplan et al 2010). Metal stents were originally used for the relief of end-stage malignant disease, where the ureteral stricture ws either directly caused by the tumor or indirectly via pressure of a tumor on the ureter.…”

“…An in vitro study has shown that this metal stent provides its best drainage when the ureter is tightly compressed onto its outer surface which is likely due to the result of increased flow between the coils of the metal stent. It was this feature that makes the Resonance TM stent useful in patients in which the ureter is obstructed due to malignancy (Blaschko, Deane et al 2007;Liatsikos, Karnabatidis et al 2009;Masood, Papatsoris et al 2010;Sountoulides, Kaplan et al 2010;Wang, Lee et al 2010;Benson, Taylor et al 2011). …”