Understanding Biliary Stents: Covered, Uncovered and Everything Between

Biliary strictures — whether from malignant obstruction or benign scarring — are commonly managed endoscopically or percutaneously with self-expandable metal stents (SEMS). The Niti-S biliary range we distribute covers several distinct construction approaches, and picking the right one usually comes down to three questions: is the stricture benign or malignant, does it need to resist tumor ingrowth, and does it need to be removable?

Construction: Braided vs. Weaving

Two base constructions show up repeatedly across the range:

• Fixed-cell (braided) designs, like the S Biliary Stent, prioritize flexibility and fracture resistance. Atraumatic ends reduce edge hyperplasia, which matters for longer-term placement.
• Unfixed-cell (weaving) designs, like the D Biliary Stent, foreshorten less and conform more readily to tortuous anatomy — useful where accurate positioning in a curved duct is the priority.

Covering Options

• Uncovered stents (S Biliary Stent Uncovered, D Biliary Stent) are typically used for malignant strictures where tissue in-growth through the mesh helps anchor the stent, and removal isn’t the goal.
• Fully or partially covered stents (S Biliary Stent Covered, S Flare, COMVI) add a silicone or PTFE layer to resist tumor ingrowth and, in benign disease, allow the stent to be removed later. The S Flare design adds differently-angled flared ends specifically to resist migration in fully covered configurations.
• COMVI takes covering a step further with a triple-layer construction — a PTFE membrane sandwiched between inner and outer nitinol mesh — combining an unfixed-cell structure’s conformability with a covered stent’s resistance to tissue invasion.

Purpose-Built Variants

A few designs solve specific procedural problems:

• M Biliary Stent and LCD™ are built for hilar strictures, where two stents often need to sit side-by-side. Both use a slim delivery system (down to 6Fr) so two devices can be introduced into the same working channel simultaneously — LCD adds a large-cell structure specifically to make second-stent placement and stent-in-stent procedures easier.
• BUMPY™ and BUMPY™ String are designed around benign strictures and post-transplant anastomoses, where the priority shifts to protecting side-branch ducts (via irregular cell sizing) and easy, atraumatic removal (via a long retrieval string).
• KAFFES™ adds a distinctive mid-body waist for added radial force in short, post-transplant anastomotic strictures, again with a long retrieval string for removal from high positions in the CBD.
• GIOBOR™ is purpose-built for EUS-guided hepaticogastrostomy — roughly 70% of its length is covered to prevent bile leakage, with the remaining bare portion positioned to avoid blocking hepatic duct side branches.

Choosing Between Them

In practice, the decision tree usually looks like: benign or malignant → covered or uncovered → does the anatomy call for a braided or weaving structure → does the procedure need a specific delivery format (short-wire exchange, side-by-side hilar placement, EUS-guided access). If you’re weighing options for a specific case, our team can walk through sizing (6–10mm diameter, 4–12cm length across most of the range) and delivery system compatibility.

This is a general overview based on manufacturer product literature, not clinical guidance. Device selection should always be made by the treating clinician based on the specific case.