Endoscopic biliary stenting for unresectable malignant hilar obstruction

Palliative drainage is the primary treatment option for unresectable malignant hilar biliary obstruction (UMHBO) to improve the prognosis and quality of life. Currently, endoscopic biliary drainage is considered as a first-line treatment for UMHBO as well as for distal biliary obstruction. Self-expanding metal stents (SEMSs) are preferred over plastic stents (PSs) in patients with life expectancy of >3 months. However, endoscopic treatment of UMHBO is often more challenging and complex than that of distal biliary obstruction. Although no consensus exists on the optimal method for biliary drainage because of the lack of well-designed, large-scale randomized control trials, several essential aspects of various optimal methods have been studied. Presently, technological developments in this field are under way and newly designed or modified stenting devices for UMHBO are being developed. In this review, we assess the optimal stenting strategy for UMHBO based on the previous literature, focusing on the stent type (PS vs SEMS), the liver volume to be drained, unilateral (single) vs bilateral (multiple) stent deployment, and bilateral stenting method (stent-in-stent vs side-by-side).