A bile duct stent is a small, hollow tube placed inside the bile duct system to restore the flow of bile from the liver to the small intestine. Placement is typically performed using an endoscope in a technique known as Endoscopic Retrograde Cholangiopancreatography (ERCP). The stent bypasses obstructions caused by gallstones, scar tissue, or tumors, preventing the buildup of bile that causes jaundice and infection. Although the stent keeps the narrowed duct open, it is usually not a permanent fixture. Its temporary nature is necessary because the presence of this foreign object inevitably leads to its failure over time.
Why Stents Become Blocked
The most common reason a bile duct stent must be removed is occlusion, or clogging. Bile is a non-sterile fluid containing various components, and the stent acts as a scaffold for biological material to accumulate. This material includes food particles, calcium salts, cholesterol crystals, and shed epithelial cells, which gradually narrow the tube’s interior.
Bacteria migrating upward from the small intestine significantly contribute to this blockage. These bacteria colonize the stent surface and form a sticky, protective layer called a biofilm. The biofilm traps the solid components of the bile, creating a thick sludge that eventually seals off the stent’s inner channel.
When the stent completely occludes, bile flow stops, and pressure builds up behind the blockage. This results in symptoms like jaundice, fever, and abdominal pain, often signaling a serious infection called cholangitis. To restore drainage and prevent life-threatening infection, the blocked stent must be promptly removed and replaced.
Material Type Dictates Lifespan
The lifespan of a bile duct stent is influenced by its material, which dictates the scheduled time for removal or replacement. Plastic stents, often made from polyethylene, are a short-term solution. They are highly susceptible to biofilm and sludge buildup, requiring replacement every three to six months to prevent full blockage.
Metal stents, specifically self-expanding metal stents (SEMS), are made from alloys like nitinol and have a much larger diameter. Their wider bore and different surface properties allow them to resist clogging for a longer period, often remaining patent for six to twelve months or more. If the obstruction is caused by a tumor and the patient’s prognosis is limited, a metal stent may be placed with the intention of remaining permanent.
Even SEMS are not immune to failure, as tissue can grow through the meshwork or cover the ends of the stent, causing re-obstruction. The choice between plastic and metal is a strategic decision based on the expected duration of the obstruction and the patient’s overall health. Both types require monitoring and potential intervention.
Urgent Reasons for Early Removal
Beyond the gradual process of clogging, unexpected complications necessitate the urgent removal or repositioning of a bile duct stent. Stent migration occurs when the device moves out of its intended position. If the stent slips downward into the duodenum or upward into the bile duct, it becomes ineffective at draining bile and can cause pain or recurrent blockage.
Mechanical failure, such as fracturing or kinking, is another reason for immediate intervention. Although rare, the stent can also cause injury to surrounding tissue, such as a duct wall perforation, which is a medical emergency. Symptoms like sudden, severe abdominal pain or a rapid return of jaundice signal these urgent complications, requiring prompt endoscopic or surgical attention.
How Stent Replacement is Performed
The procedure to remove and replace a bile duct stent is performed using the ERCP technique. The patient is sedated, and the endoscope is guided through the mouth, stomach, and into the small intestine where the bile duct opening is located. The doctor visualizes the old stent and uses specialized tools, such as grasping forceps or a retrieval balloon, to carefully pull the stent out through the endoscope.
Many stents are designed with a small loop or flange to make retrieval easier. Once the blocked stent is removed, a new stent is usually inserted immediately during the same procedure to maintain bile flow. The entire process is completed quickly, and most patients are monitored for a few hours before being discharged.