Comparison Between Novel Flower-type Covered Stent and Conventional Covered Stent

Inclusion Criteria: * Adults from 19 to 85 years of age who have voluntarily agreed to the clinical trial and signed a written agreement * Patients with malignant extrahepatic bile duct obstruction without surgery Exclusion Criteria: * Patients who had already undergone surgical biliary drainage * Patients who previously underwent percutaneous spinal cholecystectomy (PTGBD) * Patients who underwent conventional metal-on-metal self-expandable metal stents (C-CSEMS) * Patients who underwent biliary plastic stent implantation for more than 15 days * Patients with malignant stricture of the intrahepatic bile duct and patients with stenosis within 2 cm of the liver * Patients whose expected life expectancy is less than 3 months * Pregnant patient * Patients who can not undergo endoscopic procedures based on the judgment of the researcher