In an adult patient with unresectable malignant biliary obstruction, what are the risks and benefits of fully covered self‑expandable metal stents versus uncovered self‑expandable metal stents versus plastic biliary stents?

Stent Selection for Malignant Biliary Obstruction

For unresectable malignant distal biliary obstruction, use self-expandable metal stents (SEMS) over plastic stents, with fully covered SEMS (FCSEMS) or partially covered SEMS (PCSEMS) preferred over uncovered SEMS (UCSEMS) when survival is expected to exceed 4 months.

Metal Stents vs Plastic Stents

Metal stents are superior to plastic stents for patients with projected survival >4 months 1. The evidence is compelling:

• Patency: Metal stents maintain 81% patency at 6 months versus only 20% for plastic stents 1
• Reinterventions: Significantly fewer required with metal stents 1
• Cost-effectiveness: Despite higher upfront costs, SEMS are both more effective and less costly than plastic stents due to reduced need for repeat procedures and hospitalizations 2

Plastic stents may be considered only for:

• Patients with survival <3-4 months
• Tumors potentially responsive to chemotherapy/radiotherapy where obstruction may resolve
• Bridge to surgery in resectable cases

Covered vs Uncovered Metal Stents

The choice between FCSEMS, PCSEMS, and UCSEMS involves trade-offs:

Fully Covered SEMS (FCSEMS)

Benefits:

• Longer stent patency (445 vs 348 days compared to UCSEMS) 3
• Prevents tumor ingrowth most effectively 4
• Removable if needed 1

Risks:

• Higher migration rates (2.34-fold increased risk) 5
• Increased acute cholecystitis risk in patients with intact gallbladder 4
• Tumor overgrowth more common than UCSEMS 5

Partially Covered SEMS (PCSEMS)

Benefits:

• Intermediate migration risk between FCSEMS and UCSEMS
• Does NOT show increased cholecystitis risk compared to UCSEMS 4
• Comparable patency to FCSEMS 6

Risks:

• Some tumor ingrowth still possible
• Cannot be removed as easily as FCSEMS

Uncovered SEMS (UCSEMS)

Benefits:

• Lowest migration rates 5, 4
• Lowest tumor overgrowth rates 4
• Lowest sludge occlusion rates 4

Risks:

• Tumor ingrowth (4-fold higher than FCSEMS) 5
• Cannot be removed once deployed 1
• Shorter patency duration 3

Clinical Decision Algorithm

Step 1: Confirm unresectable malignant distal biliary obstruction requiring palliation

Step 2: Assess expected survival

• If <3-4 months → Consider plastic stents
• If >4 months → Proceed with SEMS

Step 3: Select SEMS type based on patient factors:

Choose PCSEMS if:

• Intact gallbladder present (avoids cholecystitis risk of FCSEMS) 4
• Standard anatomy
• Pancreatic cancer etiology

Choose FCSEMS if:

• Prior cholecystectomy (eliminates cholecystitis concern)
• Need for potential stent removal anticipated
• Non-pancreatic cancer etiology 3

Choose UCSEMS if:

• High migration risk (short stricture, crossing gastroesophageal junction equivalent)
• Concerns about tumor overgrowth
• Cost constraints in settings where reintervention is readily available

Critical Caveats

1. Gallbladder status is crucial: FCSEMS significantly increases acute cholecystitis risk in patients with intact gallbladder 4. This is NOT seen with PCSEMS 4.

2. No survival difference: Despite differences in patency, no SEMS type has demonstrated improved overall survival 3, 5, 6, 4. The choice impacts quality of life through reduced reinterventions.

3. Migration with covered stents: The silicone coating that prevents ingrowth also increases migration risk 1, 5. Consider stent anchoring techniques (endoscopic suturing, over-the-scope clips) for FCSEMS 7.

4. Endoscopic sphincterotomy increases occlusion risk: EST is an independent risk factor for stent occlusion (HR 1.26) 3. Avoid if not technically necessary.

5. Recent evidence shows equivalence: The most recent 2026 RCT-only network meta-analysis found no significant differences in recurrent biliary obstruction or overall survival between FCSEMS, PCSEMS, and UCSEMS 4, though each has distinct complication profiles.

Practical Recommendation

For most patients with unresectable malignant distal biliary obstruction and intact gallbladder, use PCSEMS as first-line therapy 6, 4. This provides the patency benefits of covered stents without the increased cholecystitis risk of FCSEMS, while maintaining lower migration rates than FCSEMS. Reserve FCSEMS for post-cholecystectomy patients or when stent removal may be needed.