Introduction

Acute pancreatitis (AP) accounts for approximately 230,000 hospital admissions per year in the United States alone. A growing concern is that 20% of cases develop a severe form of the disease, associated with a mortality risk ranging from 10% to 30% [1]. Gallstone disease remains the most common cause of AP (40-70%), predominantly affecting women, while excessive alcohol consumption ranks second (25-30%) and is more commonly associated with AP in men [2].

Although most cases follow a mild and self-limited course, 10% to 20% progress to severe disease with systemic and local complications that worsen organ failure and increase the risk of mortality [3]. Peripancreatic fluid collections (PFCs) are recognized complications of AP and result from disruption of the pancreatic duct, leading to fluid accumulation in the retroperitoneal or peripancreatic spaces [4].

According to the revised Atlanta classification (2012), these collections are classified as acute peripancreatic fluid collections and pancreatic pseudocysts, the latter considered a late complication occurring after four weeks of evolution [4]. In addition, pancreatic necrosis (5-10%) may lead to acute necrotic collections or walled-off necrosis (WON), characterized by a well-defined radiological capsule that develops late (>4 weeks) [5]. Understanding the concept of a “wall” is essential from an endoscopic perspective, as it allows safe puncture into a confined and well-demarcated cavity [6].

Most pancreatic pseudocysts are asymptomatic and tend to resolve spontaneously; however, those persisting beyond six weeks or associated with clinical symptoms require drainage. Drainage may be performed via a transpapillary endoscopic approach in cases with communication to the pancreatic duct, or via transmural drainage when the pseudocyst is directly adjacent to the gastroduodenal wall [7].

Historically, patients with necrotic collections underwent laparotomy; however, this approach was associated with high complication and mortality rates. This paradigm has changed dramatically over the past 20 years. Following the publication of the PANTER trial in 2010, a step-up approach was proposed for the management of necrotic collections using minimally invasive techniques, which allow a progressive treatment strategy based on the patient’s clinical evolution [2,8]. This approach has demonstrated success rates of 97% to 99%. Similarly, the PENGUIN trial (2012) showed that endoscopic necrosectomy is associated with fewer complications, establishing the step-up approach as the current standard of care [9,10].

Current indications for drainage include symptomatic or infected pseudocysts or pancreatic necrosis [11]. It is also indicated in cases of extrinsic compression causing intestinal or biliary obstruction, as well as abdominal compartment syndrome. Early drainage (<2 weeks) should generally be avoided, and delayed drainage (>3-4 weeks) is preferred whenever clinically feasible [12].

Initially, endoscopic drainage was performed by “blind” puncture of the submucosal bulge caused by large collections, increasing the risk of complications such as bleeding and perforation. In recent years, endoscopic ultrasound (EUS)-guided drainage has been widely adopted and has progressively become the standard of care [7]. EUS plays a key role in the evaluation and management of PFCs and allows drainage using the main technique: a single-step technique using a linear EUS scope, allowing puncture through the working channel, guidewire placement, tract dilation with a balloon, and stent deployment [8].

Stents used for this procedure may be plastic or metal. Metal stents have shown better outcomes due to their larger luminal diameter and facilitation of endoscopic necrosectomy. Among them, lumen-apposing metal stents (LAMS) are designed to minimize the risk of migration [12]. Hot LAMS feature an electrocautery-enhanced delivery system. They allow the endoscopist to puncture and deploy the stent in one streamlined step directly through the target wall, which reduces procedural time and lowers the risk of losing access to the target area. Cold LAMS lack a built-in cautery tip. They require a multi-step approach: puncturing the target with a needle, placing a guidewire, dilating the tract with a balloon, and then manually passing the stent over the wire.

Despite high technical success rates of EUS-guided drainage, immediate or delayed complications may occur. These are often related to complex anatomical locations, such as collections in the uncinate process or those located more than 1 cm from the gastroduodenal wall, as well as stent migration, obstruction, bleeding, or perforation [6].

Nevertheless, EUS-guided drainage is associated with high technical and clinical success rates; therefore, transmural drainage is currently considered the standard of care for patients with peripancreatic collections [6].