A scanning electron microscopic study of biliary stent materials

Background: Clogging of biliary stents remains an important problem. In vit ro studies have shown less sludge formation in Teflon stents. Recently, cli nical studies with Teflon stents have produced contradictory results. The a im of this study was to investigate whether the surface properties of the e ndoprostheses could explain the variation observed in clinical studies. Methods: A total of 9 different types of unused 10F endoprostheses were exa mined by scanning electron microscopy (SEM): polyethylene Amsterdam-type, p olyurethane Amsterdam-type, Teflon Amsterdam-type, Teflon Tannenbaum-type a nd a Tannenbaum-type stent with a thin stainless steel mesh between inner a nd outer layers. Results: All polyethylene stents had a relief with tiny lumps. All Teflon s tents had multiple shallow pits and ridges along the entire longitudinal ax is. Both Tannenbaum-type stents also had multiple particles protruding into the stent lumen with adjacent holes in the wall of the stent. The polyuret hane stent had an extremely smooth surface. Conclusion: SEM of Teflon made stents showed a markedly irregular inner sur face, which may explain the controversial results of clinical studies. Our results indicate that the inner surface of a new stent should first be eval uated by SEM before clinical trials are initiated.