Meta-analysis of randomized trials comparing the patency of covered and uncovered self-expandable metal stents for palliation of distal malignant bile duct obstruction

Background: Self-expandable metal stents (SEMSs) are used for palliation of malignant biliary obstruction.

Objective: We performed a meta-analysis to compare stent patency and stent survival of covered SEMSs (CSEMSs) and uncovered SEMSs (USEMSs) in patients with unresectable distal malignant biliary obstruction.

Design: Meta-analysis.

Setting: Tertiary-care facility.

Patients: A comprehensive search of several databases (from each database's earliest inclusive dates to November 2010, any language, and any population) was conducted. The search identified 337 potential abstracts and titles, of which 16 were retrieved in full text. Review of references identified 17 additional studies. We found 5 multicenter, randomized trials involving 781 patients.

Intervention: Placement of covered and uncovered SEMSs for treatment of distal malignant biliary obstruction.

Main outcome measurements: Stent patency, stent survival, patient survival, and cause for stent dysfunction (ingrowth, overgrowth, migration, and sludge formation).

Results: The median length of follow-up was 212 days. Compared with USEMSs, CSEMSs were associated with significantly prolonged stent patency (weighted mean difference [WMD] 60.56 days; 95% confidence interval [CI], 25.96, 95.17; I² = 0%) and longer stent survival (WMD 68.87 days; 95% CI, 25.64, 112.11; I(2) = 79%). Stent migration, tumor overgrowth, and sludge formation were significantly higher with CSEMSs (relative risk [RR] 8.11; 95% CI, 1.47, 44.76; I² = 0%), (RR 2.02; 95% CI, 1.08, 3.78; I² = 0%), (RR 2.89; 95% CI, 1.27, 6.55; I² = 0%).

Limitations: Relatively low number of studies available and the fact that 2 of the 5 studies were from one institution. Also, the limited availability of some stents used in the trials may limit the applicability of these results.

Conclusion: CSEMSs have a significantly longer duration of patency compared with USEMSs in patients with distal malignant biliary obstruction. Stent dysfunction occurs at a similar rate, although there is a trend toward later obstruction with CSEMSs.