Two-in-one Covered and Uncovered Metal Stent

Endoscopic placement of a self-expandable metal stent (SEMS) is the principle method for palliation of inoperable malignant distal biliary obstruction. As the survival time for those patients has improved due mainly in part to development of chemotherapeutic intervention, it is becoming important to prevent recurrent cholangitis and liver failure by prolonging the SEMS patency, leading to continuation of chemotherapy and better prognosis. Therefore, one-time stent insertion before disease-progression-related death is an ultimate goal of developing an ideal biliary stent. SEMSs have been found to be superior to plastic stents in terms of the stent patency, because it prevent accumulation of biliary sludge owing to larger diameter. The ideal designs of biliary SEMSs for prolongation of the stent patency include 1) bare metal mesh for tissue embedding to prevent stent migration, 2) covering material to counteract neoplastic tumor ingrowth, and 3) anti-reflux structure to reduce enteric biliary reflux. However, none of bare, covered, and anti-reflux metal stent alone constantly demonstrated superiority over the others in the stent patency. To compensate for the limitations of each stent, a double stent system in which both covered and bare SEMSs are integrated into one stent system was introduced in the field of the interventional radiology, but further data accumulation is needed to assess the comparability with various conventional SEMS types in terms of stent patency, reintervention efficacy, and clinical outcomes following reintervention, because in this system two metal stents are implanted at once exclusively via percutaneous route and clogged inner covered stent cannot be removed at the time of the reintervention. Recently a new covered and uncovered SEMS in which the clogged inner stent can be endoscopically removed leaving the outer stent in place, was introduced. In the current study, we aimed to evaluate the efficacy and safety of this stent in patients with inoperable malignant distal biliary obstruction.