Development of an ideal self-expandable metallic stent design

There are various types of self-expandable metallic stent (SEMS) for biliary obstruction, but it is unknown which one is ideal. Ideal SEMS should prevent recurrent biliary obstruction or other complications after SEMS placement until the patient's death. In this review, risk factors for recurrent biliary obstruction or complications are discussed. Based on the current literature, the combination of a high radial force and a low axial force is important. SEMS should be fully covered with a smooth inner surface to prevent stent occlusion by tumor ingrowth, sludge, or food impaction. There are attempts to further prolong time to recurrent biliary obstruction: a large bore SEMS to prevent stent occlusion by sludge or a SEMS with antimigration systems. Taking these results of various SEMS into consideration, an ideal biliary SEMS should be further developed.