RESUMEN
BACKGROUND/AIMS: In order to provide a complete obstacle to tumoral growth, we designed a new self-expandible metal stent fully covered with polyurethane membrane. The purpose of the study was to compare the safety and effectiveness of a new membrane-covered Niti-S stent versus conventional uncovered Wallstent. METHODS: In a prospective trial, 59 patients with malignant extrahepatic biliary obstruction received either a newly developed covered metal stent (Niti-S stent, 30 cases) or an uncovered metal stent (Wallstent, 29 cases) by the endoscopic transpapillary route. RESULTS: Effective biliary decompression was achieved in all patients initially, and short-term results were similar in both groups. Stent failure was observed in 4 of the 30 patients (13%) after a median period of 165 days in the Niti-S group and in 8 of the 29 patients (28%) after a median period of 152 days in the Wallstent group. The reasons of stent failure were occlusion (n=3) and migration (n=1) in the covered Niti-S stent group and occlusion (n=8) in uncovered Wallstent group. According to the Kaplan-Meier life table analysis, the patency rates after 90, 180, and 360 days were 100%, 90%, and 74% in covered Niti-S stent group and 100%, 73%, and 61% in uncovered Wallstent group respectively. The occluded membrane-covered Niti-S stent was easily removed endoscopically and a new Niti-S stent was reinserted in one patient. CONCLUSIONS: The new, membrane-covered Niti-S stent has a lower stent failure rate and a tendency toward long-term patency rate compared to uncovered Wallstent. The covering may effectively prevent tumor ingrowth and it is sometimes possible to remove an occluded Niti-S stent.