4646 “bare” versus “polyurethane covered” selfexpandable metallic stent for malignant biliary obstruction.

Background Obstruction of the self-expandable metallic stents (EMS) due to tumor ingrowth is the most important problem of biliary endoprosthesis. To prevent this complication, a polyurethane covered EMS (covered EMS) have been developed. The present study compared the clinical efficacy of the covered EMS to that of the uncovered EMS (bare EMS). Patients and Method One hundred forty-six patients with malignant biliary obstruction (96 males and 50 females; a mean age of 71.9 year-old) were enrolled in this study. Malignant tumors that caused the biliary obstruction include pancreatic carcinoma (n=45), bile duct carcinoma (n=45), gallbladder carcinoma (n=17), and others (n=39). Four kinds of EMS were employed for biliary endoprosthesis with or without polyurethane covering; Gianturco-Z stent (bare/covered, n=63/0),Wallstent (n=54/0), Spiral-Z stent (n=1/20), and Ultraflex Diamond Biliary Stent (n=3/5). The EMS was placed by the percutaneous transhepatic approach in 77 patients, and by the endoscopic approach in 69 others. Results During the follow-up period, obstruction of the stent was observed in 35 (28.9 %) of 121 bare EMS and 3 (12.0%) of 25 covered EMS. The 6 months patency rate of the bare EMS and covered EMS were 68.7 % and 87.1 %, and 1 year patency rate of them was 72.5 % and 39.7%, respectively. There was no statistical difference between bare EMS and covered EMS. Presumably, obstruction in the bare EMS was caused by tumor ingrowth in all cases, and obstruction of the covered EMS were tumor ingrowth due to damage of polyurethane membrane and overgrowth in 1 case and sludge formation inside the stent bore in 2 cases. Discussion Although it has been predicted that covered EMS stents may have a longer patency period than the bare EMS, there is no statistically significant difference in the stent patency. It may becomes some problems that the damage of polyurethane membrane during or after stent deployment, adhesion of biliary sludge to the stent bore and tumor overgrowth. Conclusion The clinical efficacy of polyurethane covered EMS for malignant biliary obstruction was not determined in this study.