3. Technical success of procedure performed for restoration of bile duct drainage, overall and stratified by treatment group Sludge group: Ability to restore stent patency by cleaning the stent content followed by cholangiographically or cholangioscopically confirmed restored stent patency Ingrowth / overgrowth group: Ability to perform biliary radio frequency ablation (RFA) followed by cholangiographically or cholangioscopically confirmed restored stent patency