Stents with specialized functions: drug-eluting stents and stents with antireflux devices

Biliary drainage in malignant biliary obstruction improves patient survival and quality of life. Although bypass surgery was historically the main method of treating malignant biliary obstruction, stent insertion using endoscopy or interventional radiology is currently recognized as the first-line of treatment. Biliary stents have undergone various modifications in terms of material and structure, with the aim of increasing stent patency. One such modification is the antitumor-agent-eluting stent, which is intended to suppress tumor ingrowth through chemical changes in the membrane. Another modified stent is the antireflux stent, which physically prevents the reflux of food by using an antireflux valve. Although the safety of these modified stents has been demonstrated in both animal and human studies, their efficacy, compared with conventional stents, remains unknown. Although the development of these functional stents is challenging, their potential is promising. Effort is necessary to increase stent patency, which requires much modification and development, to prolong patient survival.