Inoperable Malignant Biliary Obstruction

This study looks at the best way to treat bile duct blockage in people with advanced cancer that cannot be removed by surgery. A blocked bile duct can cause serious symptoms like yellowing of the skin (jaundice), infection, and pain. A common procedure called ERCP sometimes doesn't work in these patients. A newer method called EUS-guided choledochoduodenostomy (EUS-CDS) uses internal ultrasound to place a special metal tube (called a LAMS) to allow bile to drain. However, over time this stent can still become blocked. To reduce this risk, doctors can place a second stent inside the first. This study is comparing two types of these second stents: * A plastic stent (double pigtail stent or DPS) * A metal stent (fully covered self-expanding metal stent or FCSEMS) The study will include patients at Waikato Hospital. After the first stent is placed, they will be randomly assigned to receive either a DPS or FCSEMS. Patients will be followed for 6 months to see how well the stents work. The aim is to find out which approach keeps the bile duct open longer and reduces the need for further procedures or hospitalisation, helping improve care and comfort for people with advanced cancer