Previous studies indicated that covered stents are less likely to become occluded in comparison to bare stents. While the probability of occlusions caused by tumor in-growth is less in covered stents, they are more likely to spontaneously migrate to a position that is distal to the original deployment site. However, newer covered stents with improved designs, such as the partially covered double bare metallic stent used for this study, include features to mitigate the migration issue. The purpose of this study is to confirm whether the difference in patency rate between regular covered stents and bare stents, which has already been well established by existing studies, is also reproducible when double covered stents are compared against double bare stents.

Malignant obstructive jaundice is a common complication of advanced stage cholangiocarcinoma, GB cancer, and pancreatic cancer. In biliary stricture by malignancy, biliary drainage with placement of self-expanding metal stent (SEMS) for palliation is the therapy of choice in these patients. When compared to plastic stents, SEMS present a significantly decreased risk of recurrent biliary obstruction. SEMS are also more cost-effective than plastic stents in patients with a life expectancy of longer than 4 months. However, despite their numerous benefits, SEMS become occluded in up to 50 % of patients in the first 6-8 months. In order to minimize the occurrence of this issue, covered stents were developed. Previous studies indicated that covered stents are less likely to become occluded in comparison to bare stents. While the probability of occlusions caused by tumor in-growth is less in covered stents, they are more likely to spontaneously migrate to a position that is distal to the original deployment site. However, newer covered stents with improved designs, such as the partially covered double bare metallic stent used for this study, include features to mitigate the migration issue. The purpose of this study is to confirm whether the difference in patency rate between regular covered stents and bare stents, which has already been well established by existing studies, is also reproducible when double covered stents are compared against double bare stents.

Inclusion Criteria:

• Pathologically confirmed malignant biliary obstruction or clinically defined malignant biliary obstruction
• malignant biliary obstruction was located more than 1cm from the hilum
• older than 20 years old
• Life expectancy > 6 months
• Inoperable case due to advanced stage or comorbidity
• Informed consent obtained

Exclusion Criteria:

• Inadequate case for ERCP
• Failed endoscopic approach to duodenum or biliary tract
• biliary obstruction was located at hilum or IHD
• patients with uncontrolled infection
• Pregnancy
• No signed informed consent