A biliary stent is a small, hollow tube placed inside the bile duct system to keep a blocked or narrowed passage open. This device ensures that bile, a digestive fluid produced by the liver, can properly drain into the small intestine. The stent’s function is to restore the normal flow of bile, addressing blockages that can lead to serious health issues like infection and jaundice.
Anatomy of the Biliary System
The biliary system is a network of ducts that transports bile from the liver to the small intestine. Bile is first collected by small ducts within the liver, which merge to form the right and left hepatic ducts. These then join outside the liver to create the common hepatic duct.
The common hepatic duct eventually joins with the cystic duct, which comes from the gallbladder, to form the common bile duct. This duct runs down to the first part of the small intestine, the duodenum. It enters the duodenum at a muscular opening known as the major duodenal papilla, also called the papilla of Vater. The biliary stent is typically placed across a stricture or blockage within this duct system, most often in the common bile duct.
Why Stents Are Needed
A stent becomes necessary when the flow of bile is obstructed, causing bile to back up into the liver and bloodstream, which leads to jaundice and infection. The most frequent need for a biliary stent arises from malignant obstructions, often caused by cancers of the pancreas, bile duct (cholangiocarcinoma), or liver. These tumors press on the ducts from the outside, causing significant narrowing.
Stents are also used for benign obstructions. These include strictures, which are narrowings caused by scar tissue from previous surgery or inflammation. Gallstones lodged in the common bile duct (choledocholithiasis) can also necessitate temporary stenting until the stones are removed. Stents are sometimes used to manage bile leaks that occur as a complication following gallbladder surgery.
How Biliary Stents Are Placed
The placement of a biliary stent is a specialized procedure, with the pathway determined by the location and cause of the blockage. The most common method is Endoscopic Retrograde Cholangiopancreatography (ERCP), which is an internal approach. During ERCP, a flexible endoscope is guided through the mouth, past the stomach, and into the duodenum.
The endoscopist guides the scope to the papilla of Vater, where the bile duct enters the small intestine. A thin wire is advanced through the papilla and into the bile duct, crossing the area of blockage. Contrast dye is injected under X-ray guidance to visualize the obstruction and accurately size the stent. The stent is then delivered over the guidewire and positioned to span the narrowed section, ensuring one end is above the blockage and the other extends into the duodenum.
When ERCP is not feasible, such as in patients with altered anatomy from previous surgery, Percutaneous Transhepatic Cholangiography (PTC) is used. This procedure involves an interventional radiologist inserting a fine needle directly through the skin and liver into a bile duct.
Using X-ray guidance, the doctor injects contrast dye to locate the obstruction and passes a guidewire across the blockage. The stent is delivered over this wire to keep the duct open, providing a pathway for bile to drain either internally into the small intestine or temporarily externally into a bag. The PTC technique is often reserved for complex blockages, particularly those high up near the liver.
Types of Biliary Stents
Biliary stents are primarily categorized by the material they are made from. Plastic stents are constructed from medical-grade polymers, such as polyethylene or polyurethane, and are typically used for temporary drainage. They are less expensive and easier to remove, making them the preferred choice for benign conditions, like gallstones or inflammation-related strictures. However, their smaller diameter means they are prone to clogging and often require replacement every three to six months.
Self-expanding metal stents (SEMS) are made from flexible alloys like nitinol (nickel-titanium) and are designed for long-term placement. Once deployed, the mesh-like stent expands to a much larger diameter than a plastic stent, significantly lowering the risk of re-blockage. Metal stents are most often chosen for patients with malignant obstructions, such as pancreatic cancer, where the goal is long-term palliation. These stents may be fully covered to prevent tissue ingrowth or uncovered to anchor them securely in place.