Long-term outcome of the WallFlex partially covered stent for unresectable malignant biliary obstruction: a multicenter single-arm prospective study.

Covered metallic stent was developed to prevent tumor ingrowth. However, procedural accidents due to its insertion often occur and migration after long-term insertion causes problems. The WallFlex partially covered stent (WF) with reduced axial force enables stenting along the bile duct. We examined the usefulness of WF placement in an unresectable malignant distal biliary obstruction.We examined procedural accidents, stent obstruction rate, and patency period caused by WF insertion.Ninety-seven patients were analyzed; procedural accidents caused by WF insertion occurred in 8 patients (7.2%) composed of acute cholecystitis in 3 patients (3.2%), acute pancreatitis in 2 patients (2.1%), acute cholangitis in 1 patient (1%), and other in 1 patient (1%). The stent obstruction rate was 19.6% (19 patients), and obstruction cause includes sludge in 9 patients (9.3%), migration in 4 patients (4.1%), food impaction in 3 patients (3.1%), ingrowth in 1 patient (1%), overgrowth in 0 patients (0%), and unknown in 2 patients (2.1%). The mean stent patency period was 634.918 +/- 66.545 (7-946) days.WF has less procedural accidents when inserted into unresectable malignant biliary obstruction patients with reduced migration rate after a long period and low obstruction rate.