Ni-Cr-Co alloy ureteral stent: scanning electron microscopy and elemental analysis characterization after long-term indwelling.

We report the first preliminary study on metal-alloy ureteral stent after long indwelling times. The aim is to analyze by physical-chemical characterization of the stent after use and to evaluate the material performance in this human in vivo case study. Six Resonance metallic stents (Cook Ireland) were inserted in six patients for 6, 10, 11, 12, 24, and 36 months. The stents were then collected and studied by Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectroscopy (EDS), gaining information about the metal stent surface and the amount and nature of the formed encrustation. The stents were all draining adequately, despite the presence of the bacterial biofilm layer in all stents. This layer was more dense and compact as the indwelling time increased. Some slight precipitation of inorganic compounds, such as brushite and calcium oxalate was observed. No epithelial tissue in growth was recorded. These preliminary results with Resonance metallic ureteral stents suggest the feasibility of a long-term approach in patients with chronic ureteral obstruction. The durability of the metal stent, the lack of epithelial tissue ingrowths and limited pain or discomfort to patients were proven over long time periods. The long-term use of these stents is therefore feasible, avoiding the continuous exchange of the stent, decreasing hospital costs and increasing the quality of life of patients affected by malignant pelvic tumors.