What is the management approach for a patient with walled-off necrosis in the context of acute pancreatitis?

Management of Walled-Off Necrosis (WON)

Walled-off necrosis requires a delayed, step-up approach starting with drainage (endoscopic preferred over percutaneous) at least 4 weeks after disease onset, followed by minimally invasive debridement only if drainage alone fails, and should be managed in a specialized center with multidisciplinary expertise. 1, 2

Definition and Recognition

• WON is a mature, encapsulated collection of pancreatic and/or peripancreatic necrosis with a well-defined inflammatory wall that develops more than 4 weeks after the onset of necrotizing pancreatitis 3
• Do not mistake WON for a simple pseudocyst - the internal consistency contains solid necrotic debris requiring more aggressive management than fluid-only pseudocysts 4, 3
• Use EUS or MRI to differentiate WON from simple pseudocysts, as the presence of solid debris fundamentally changes management strategy 3

Indications for Intervention

Intervene for WON when:

• Infected necrosis is confirmed (positive cultures) or strongly suspected (gas in collection on CT, bacteremia, sepsis, or clinical deterioration) 3, 2
• Symptomatic collections causing persistent abdominal pain, gastric outlet obstruction, biliary obstruction, or persistent systemic inflammatory response syndrome 3, 2
• Persistent organ failure without infection after 4 weeks 3
• Progressive enlargement of collections or disconnected pancreatic duct syndrome 3

Do not intervene for:

• Sterile WON that is asymptomatic - these typically do not require therapy 4, 1

Timing of Intervention: The Critical 4-Week Rule

Delay all interventions for at least 4 weeks after disease onset whenever possible - early intervention (within first 2 weeks) significantly increases mortality 1, 2

• The only exceptions for early intervention (<4 weeks) are: abdominal compartment syndrome unresponsive to medical management, acute ongoing bleeding when endovascular approach fails, or bowel ischemia/acute necrotizing cholecystitis 1
• Even with these emergent indications, avoid performing necrosectomy during emergency surgery - address only the immediate life-threatening issue 5

The Step-Up Approach Algorithm

First-line: Drainage alone (without debridement)

1. Endoscopic transmural drainage is preferred over percutaneous drainage as it avoids the risk of pancreaticocutaneous fistula 2

   • Use lumen-apposing metal stents (LAMS) rather than plastic stents for superior outcomes 2
   • However, remove LAMS early (at 3 weeks) if WON is resolved on CT to avoid stent-related complications from long-term placement 6
   • Drainage alone resolves infection in 25-60% of patients without requiring further intervention 5

2. Percutaneous drainage should be considered when:

   • Patient is in the acute period (<2 weeks) and too unstable for endoscopic intervention 2
   • WON extends deep into paracolic gutters and pelvis where endoscopic access is limited 2
   • As adjunct to endoscopic drainage for complex collections 2

Second-line: Minimally invasive debridement (if drainage fails)

• Proceed to direct endoscopic necrosectomy if large-bore stent drainage alone fails after adequate trial 2
• Alternative minimally invasive surgical options include videoscopic-assisted retroperitoneal debridement or laparoscopic transgastric debridement 2
• Complete debridement of all necrotic material is essential during any intervention 1, 5

Last resort: Open surgical necrosectomy

• Reserved only for cases not amenable to less invasive approaches 2
• Associated with higher morbidity than minimally invasive techniques 2

Antibiotic Management

Do NOT use prophylactic antibiotics routinely - they do not prevent infection of sterile necrosis 1, 2

When to use antibiotics:

• Confirmed infected necrosis (positive cultures from CT-guided aspiration) 4, 3
• Strong clinical suspicion of infection (gas in collection, sepsis, clinical deterioration) 2
• Use broad-spectrum agents with good pancreatic penetration: carbapenems, quinolones, or metronidazole 2
• If prophylaxis is used in patients with >30% necrosis, limit to maximum 14 days 4, 1

Regarding CT-guided aspiration:

• Perform in patients with persistent symptoms and >30% necrosis, typically 7-14 days after onset 4, 1
• However, aspiration is unnecessary in most cases when clinical signs of infection are clear 2

Nutritional Support

Initiate early enteral nutrition to decrease risk of infected necrosis 2

• Start oral feeding immediately if patient has no nausea, vomiting, or severe ileus 1, 2
• If oral feeding not feasible, use nasogastric or nasojejunal tube feeding 1, 2
• Reserve total parenteral nutrition only for patients who cannot tolerate enteral nutrition 1, 2

Critical Care and Monitoring

• Manage all patients with extensive WON in HDU/ICU setting with continuous monitoring of vital signs, oxygen saturation, urine output, and temperature 1
• Transfer to specialized centers with multidisciplinary teams including gastroenterology, surgery, interventional radiology, critical care, infectious disease, and nutrition expertise 1, 2

Special Consideration: Disconnected Pancreatic Duct

• When disconnected left pancreatic remnant occurs after mid-body necrosis, perform definitive distal pancreatectomy in operative candidates 2
• Long-term endoscopic stenting has insufficient evidence for managing disconnected duct syndrome 2

Common Pitfalls to Avoid

• Never perform early necrosectomy (<4 weeks) unless absolute emergency indications exist - this dramatically increases mortality 1, 5, 2
• Do not rely on simple drainage alone without recognizing solid necrotic debris - this predisposes to treatment failure and infection 3, 5
• Avoid aggressive fluid resuscitation protocols that can lead to abdominal compartment syndrome 5
• Do not confuse WON with simple pseudocysts - always use EUS or MRI to assess internal consistency 4, 3

Expected Outcomes

• Overall mortality from necrotizing pancreatitis is 30-40%, but specialized centers using minimally invasive techniques report 10-20% mortality 1
• Sterile necrosis has 0-11% mortality when managed conservatively 1
• Minimally invasive treatment of even large WON (>15 cm) is feasible with only 0.7% requiring open necrosectomy and 7% procedure-related adverse events 7
• Endoscopic approaches result in shorter hospital stays and better patient-reported outcomes compared to surgical approaches 5