Randomized, Multi-Center, Comparative and Cost Effectiveness Study of a Lumen- Apposing, Covered, Self-Expanding Metal Stent (Axios™) Versus Multiple Double Pigtail Stents in the Management of Walled Off Pancreatic Necrosis

Acute pancreatitis (AP) is responsible for nearly a quarter million hospital admissions annually and will affect around 40 per 100,000 persons per year (1). The majority of patients experience a clinically mild course; however, as many as one in five patients develop a severe illness associated with a high mortality (2). In early phases of the disease, there is an acute inflammatory process that may involve necrosis of the pancreatic or peri-pancreatic tissues (3). There are also delayed complications that may develop locally, usually over a period of weeks, which include the formation of walled-off fluid collections. These are sometimes composed of simple fluid and termed pseudocysts, while in other cases they represent organization and encapsulation of sterile or infected necrosis and are termed walled-off pancreatic necrosis (WOPN) (4). The indication to drain or debride these collections usually depends upon on a number of factors, but principally on whether they are symptomatic, infected, or responsible for other local or systemic complications.

The contemporary management strategy for walled-off pancreatic fluid collections has shifted in recent years. Surgery, and even percutaneous catheter drainage, should no longer be considered the initial mainstay of therapy in place of endoscopic drainage for simple pseudocysts (5) (6). In addition there is good evidence to support an endoscopic approach for patients with infected necrosis (7). There are now numerous publications reporting the success of direct endoscopic transmural drainage or necrosectomy (ETD/N) for a variety of indications including infected and sterile walled-off collections (8).

The issue that now deserves attention is a matter of selecting the best technique to accomplish ETD/N. The current process involves first creating a cystenterostomy to gain access to the walled-off collection, dilating the tract, and then inserting a drainage device. However, there are a variety of available devices and methods in use for drainage, and to our knowledge, none to date have been directly compared in a randomized controlled trial.

The conventional approach involves inserting either a pair or more of plastic double pigtail stents or a self-expanding metal stent (SEMS) through a cystenterostomy: both approaches have limitations, and may require multiple endoscopic sessions before definitive resolution (9). One, the pigtail stents have a narrow lumen (7F-10F) and often migrate or become occluded (10). Two, the SEMS also have a tendency occlude, cause local trauma with bleeding and infection, and migrate, which has led some to also use double pigtails to help anchor the SEMS in place (11) (12).

These challenges have led to the innovation of large caliber covered stents with flanges on either end to facilitate apposition of the cyst wall and enteral tissues, preventing migration, and allowing for necrosectomy through their wide lumen. To our knowledge there are at least two designs in production; the AXIOS™ stent and the Nagi stent (13) (14). There is now a fair amount of experience, particularly using the AXIOS™ stent (with or without a novel NAVIX access system) for both WOPN and pseudocysts, with the majority of reports showing it to be safe and effective (15) (16) (17) (18) (19) (20). The device has also been successfully used for novel indications including access and drainage of the gallbladder and an intrathoracic fluid collection (21) (22) (23). The AXIOS™ stent is FDA approved for the indication of draining walled off pancreatic necrosis.