Acute pancreatitis is one of the most common diagnoses made in gastroenterology wards worldwide which causes a great deal of pain and expense along with fatal complications. Approximately, 10-20% of patients progress to necrotizing pancreatitis that result in significant morbidity and mortality. Initial conservative management may be feasible in necrotizing pancreatitis, however the majority of patients with infected necrosis or persistent symptoms will eventually require a drainage procedure. Drainage procedures for necrotizing pancreatitis include open surgery, minimally invasive surgery, percutaneous drainage, and endoscopic drainage. In the recent years, minimally invasive approaches have largely replaced open surgical necrosectomy. Endoscopic drainage of walled off pancreatic necrosis involves creation of a transmural fistula between the enteral lumen and WOPN cavity with stent placement under endoscopic ultrasound (EUS) guidance. Furthermore, direct endoscopic necrosectomy can be performed through the fistula track. The best timing for endoscopic necrosectomy is not yet defined. A recent retrospective study suggested that immediate necrosectomy after stent placement results in earlier resolution of WOPN with fewer sessions of endoscopic necrosectomy. The aim of this study is to compare immediate vs. on-demand endoscopic necrosectomy in patients with infected WOPN who undergo EUS-guided transmural drainage of WOPN.

Acute pancreatitis is one of the most common diagnoses made in gastroenterology wards worldwide which causes a great deal of pain and expense along with fatal complications (1). The incidence of acute pancreatitis is trending upward in the United States with $2.6 billion annual health care costs (2). While most patients present with mild and interstitial form of pancreatitis, 10-20% of patients progress to necrotizing pancreatitis that result in significant morbidity and mortality (3). Initial conservative management may be feasible in necrotizing pancreatitis (4), however the majority of patients with infected necrosis or persistent symptoms will eventually require a drainage procedure (5). Drainage procedures for necrotizing pancreatitis include open surgery, minimally invasive surgery, percutaneous drainage, and endoscopic drainage. Drainage procedures are typically postponed for several weeks until the necrotic cavity becomes walled off which is called walled off pancreatic necrosis (WOPN).

In the recent years, minimally invasive approaches have largely replaced open surgical necrosectomy (6). Endoscopic drainage of walled off pancreatic necrosis involves creation of a transmural fistula between the enteral lumen and WOPN cavity with stent placement under endoscopic ultrasound (EUS) guidance. Furthermore, direct endoscopic necrosectomy can be performed through the fistula track. The best timing for endoscopic necrosectomy is not yet defined. A recent retrospective study suggested that immediate necrosectomy after stent placement results in earlier resolution of WOPN with fewer sessions of endoscopic necrosectomy (7).

The aim of this study is to compare immediate vs. on-demand endoscopic necrosectomy in patients with infected WOPN who undergo EUS-guided transmural drainage of WOPN.

Infected necrosis is diagnosed with one of the following criteria in patients with WOPN three weeks after onset of acute pancreatitis (8): A. Positive Gram's stain or culture from a fine-needle aspiration; B. the presence of gas within pancreatic and peripancreatic necrosis on contrast-enhanced CT scan; C. Presence of two inflammatory variables (temperature >38.5°C or elevated C-reactive protein levels or leukocyte counts) in the absence of another focus of infection (other than infected necrosis) ; D. Presence of persistent organ failure.

Inclusion Criteria:

• Documented history of acute pancreatitis
• Necrotic collection with partial or complete wall diagnosed on CT or MRI
• Necrotic collection of any size with any number of loculations with more than 20% of solid/necrotic component
• Necrotic collection is accessible and amenable for EUS-guided drainage
• Age >= 18 years
• Suspected or confirmed infection in the necrotic collection
• The patient understands and accepts to sign the informed consent.

Exclusion Criteria:

• Irreversible coagulopathy with INR>1.5 or platelet counts <50,000
• Necrotic collection is not accessible for EUS-guided drainage
• Females who are pregnant
• Previous intervention (e,g, percutaneous drainage, or surgery) is performed for the patient

IPD will be shared with other researchers for collaborative studies upon request from the principle investigator