A Lumen-Apposing Metal Stent (LAMS) is a specialized, self-expanding, fully covered metal stent used in minimally invasive gastroenterology procedures. Its design resembles a dumbbell or saddle shape, featuring wide flanges at both ends connected by a short central segment. This structure is engineered to create a secure connection, known as an anastomosis, between two adjacent internal structures. The primary function of a LAMS is to establish a temporary conduit for draining fluid or bypassing an obstruction.
LAMS facilitates a transluminal approach, connecting a hollow organ (like the stomach or duodenum) to an adjacent structure. The wide flanges “appose” or pull the two walls together, securing the stent and reducing the risk of leakage or migration. This stable, internal passageway provides a less invasive alternative to traditional surgery. The central lumen is wide, often ranging from 10 to 20 millimeters in diameter.
Primary Use Cases for LAMS Stents
The primary application for LAMS technology is the drainage of abnormal fluid collections in the abdomen, often resulting from acute or chronic pancreatitis. These include pancreatic pseudocysts or walled-off necrosis (WON). The large-diameter lumen is beneficial for treating WON, which contains thick debris and necrotic tissue. This wide channel allows for superior fluid drainage and permits the passage of a second endoscope or specialized tools to perform direct necrosectomy (removal of solid material).
This endoscopic approach has largely replaced older methods, such as percutaneous drainage or traditional surgery, due to high success rates. Older plastic stents frequently clogged due to their smaller diameter. The unique shape of the LAMS minimizes migration risk while maximizing drainage capacity, making it the standard for managing these complex pancreatic fluid collections.
LAMS is also used in managing issues within the biliary system for patients unsuitable for surgery. For example, LAMS performs endoscopic ultrasound-guided gallbladder drainage (EUS-GBD) in high-risk patients with acute cholecystitis. A connection is created between the stomach or duodenum and the gallbladder, allowing infected bile to drain internally. This technique is also employed to bypass obstructions in the bile duct, a procedure known as choledochoduodenostomy, when the standard endoscopic route is inaccessible.
A third major application is the creation of a gastroenterostomy, or internal bypass, for treating gastric outlet obstruction. This obstruction is typically caused by tumors or scar tissue blocking the passage of food from the stomach into the small intestine. Placing a LAMS between the stomach and a segment of the small intestine establishes a new, functional channel. This allows patients to resume oral intake and often avoids the need for extensive surgical bypass procedures.
The Endoscopic Placement Procedure
Placing a Lumen-Apposing Metal Stent is performed under general anesthesia or deep sedation. The procedure relies on Endoscopic Ultrasound (EUS) guidance, which uses a specialized endoscope with an ultrasound probe. EUS allows the physician to visualize internal structures in real-time, accurately identifying the target collection or organ. This guidance is essential for mapping the path and avoiding blood vessels between the two structures, reducing the risk of bleeding.
Once the target is identified, the EUS endoscope is positioned against the wall of the gastrointestinal tract. Modern LAMS systems often integrate an electrocautery-enhanced tip, simplifying access. Using this system, the physician punctures the wall of the stomach or duodenum and enters the target structure in a single, controlled step. This cautery-assisted technique avoids the need for a separate needle, guidewire, or prior dilation.
Stent deployment is a two-step process utilizing the wide-flanged design to secure the connection. First, the delivery system is advanced through the puncture site into the target cavity, and the distal flange is released. Ultrasound confirms the correct positioning of this flange inside the collection or adjacent organ. The delivery system is then gently pulled back, seating the distal flange firmly against the inner wall of the target structure.
The second step involves releasing the proximal flange, which expands and locks into place within the gastrointestinal lumen. The short body of the stent keeps the two flanges close together, creating a secure, self-sealing connection. This resulting tract allows for immediate fluid drainage or provides the new bypass channel.
Monitoring, Management, and Stent Removal
Immediate monitoring after LAMS placement focuses on ensuring successful drainage and watching for adverse events. Fluid or bile flow through the stent is often visible immediately. Patients are monitored for symptoms like fever or severe pain, which may signal complications such as infection, perforation, or internal bleeding. The potential for bleeding or leakage is highest immediately after the procedure, requiring close observation for the first 24 hours.
The management period requires keeping the stent in place until the underlying condition resolves, which varies by indication. For draining pancreatic fluid collections, the LAMS is temporary, typically remaining for one to three months. This duration allows the surrounding tissue to heal and the fluid collection to completely collapse.
For permanent bypass indications, such as gastroenterostomy for malignant gastric outlet obstruction, the LAMS may remain indefinitely. For gallbladder drainage, the stent is temporary but may be left longer if inflammation is severe or the patient’s surgical risk is high. The decision to remove the LAMS relies on follow-up imaging confirming the resolution of the fluid collection or the patency of the bypass.
LAMS removal is a straightforward endoscopic procedure performed once the condition is resolved. The physician accesses the stent through the mouth using a standard endoscope. Specialized tools, such as grasping forceps or snares, are used to collapse the stent and pull it out through the endoscope’s working channel. Since the tract has matured and healed, removal is simpler than the initial placement. The small tract created between the two organs closes naturally over time.