3.2　Self-Expandable Metal Stent

Self-expandable metal stents（SEMS）have larger diameters than plastic stents and may provide a more durable stricture dilation effect.This was studied using covered SEMS in 13 patients by Park et al.（2008）.While the covering membrane reduces stent dysfunction from tissue in-growth and allows for future removal，stent migration was a frequent complication，occurring in five patients（38%）.Other complications include mild pancreatitis and cholestatic liver dysfunction.To overcome the problem of stent migration，a specially-designed covered SEMS（Niti-S Pancreatic Stent［bumpy type］，Taewoong Medical，Seoul，South Korea）was deployed in 32 patients（Moon et al.2010）.All the stents were easily removed at 3 months，with resolution of strictures.However，three patients developed recurrent strictures，requiring repeat stenting in two patients and surgery in one.(https://www.daowen.com)