Endoscopic strategy and covered self-expandable metal stents for malignant hilar biliary obstruction

Malignant hilar biliary obstruction (MHO), most commonly caused by cholangiocarcinoma, is an aggressive condition with a poor prognosis. Because most patients with MHO are unsuitable for primary surgical resection at presentation because of advanced age or comorbidities, palliative biliary drainage is essential to relieve obstructive jaundice and improve the quality of life. Endoscopic drainage has become the preferred palliative approach, with the choice between plastic and metal stents depending on subsequent therapeutic plans, such as systemic chemotherapy or local ablative therapies. Among biliary stents, self-expandable metal stents (SEMSs) are widely used, typically in their uncovered form. However, unlike plastic stents, uncovered SEMSs cannot be removed once deployed, and endoscopic revision is technically challenging. To improve stent patency and facilitate removability, covered SEMSs (CSEMSs) were developed, and are now commonly used in distal malignant biliary obstruction. Nevertheless, in advanced MHO, the primary use of CSEMSs remains controversial. This review summarizes recent endoscopic strategies for advanced MHO, the evolution of CSEMSs, their clinical outcomes, current limitations, and future directions.