BACKGROUND AND AIM No prospective data are available on comparing covered and uncovered self-expandable metal stent (SEMS) for reintervention of occluded uncovered metal stents during endoscopic retrograde cholangiopancreatography in patients with malignant distal biliary obstruction.

METHODS From June 2010 to November 2014, 43 patients with inoperable distal biliary obstruction of a previously placed uncovered SEMS were enrolled from three centers in Korea and randomly assigned to covered (n = 22) or uncovered SEMS group (n = 21). The primary outcome was overall stent patency. Secondary outcome was time-to-stent occlusion, patient survival, cause of stent occlusion, and adverse events.

RESULTS Overall median patency of secondary stent was 112.0 days. Median stent patency of covered and uncovered SEMS was 112.0 and 181.0 days, respectively, (P = 0.373). There was a tendency towards a longer time-to-stent occlusion in uncovered SEMS group (median: 112.0 vs 181.0 days). However, it did not reach statistical significance (P = 0.214). Most common causes of occlusion were stent clogging (36.4%) and tumor ingrowth (33.3%) in covered and uncovered SEMS groups, respectively. There was no significant difference in median survival between the groups (median: 308 vs 300 days; P = 0.325). Acute cholangitis occurred in four patients (three in covered vs one in uncovered SEMS group, P = 0.607).

CONCLUSIONS In this exploratory trial, there were no statistically significant differences in stent patency, time-to-stent occlusion, patient survival, and complication rates between covered and uncovered SEMS groups. Larger confirmatory multicenter trial is needed for the clear conclusion (ClinicalTrials.gov: NCT01315522).