[Ultrasonographic semiology of biliary prostheses]

US was used to study 60 patients with different types of plastic (Home-made, Lunderquist, Miller, Carey-Coons, Lammer) and metallic (Z-stent, Wallstent) biliary stents, from October 1990 to March 1993. The optimal US approach was assessed, together with several US features which are typical of each type of endoprosthesis. As far as plastic endoprostheses are concerned, independent of manufacturing differences, the typical US pattern on longitudinal scans is a hyperechoic double line while, on transverse scans, the prosthesis cylinder is represented by short hyperechoic lines, resembling the mathematic equal sign. According to the different types, metallic stents appear as thin hyperechoic lines or narrow gratings on longitudinal scans and as hyperechoic spots following a circular pattern or as a hyperechoic ring on transverse scans.