Pancreatic Necrosis and Pancreatic Abscess

These represent local complications of severe acute pancreatitis (see that entry for the underlying disease), occurring along a spectrum.

• Acute necrotic collection: within the first 4 weeks, containing both fluid and necrotic tissue.
• Walled-off necrosis: after 4 weeks, when a mature wall has formed around the necrotic collection.
• Infected pancreatic necrosis: arises if the necrosis becomes secondarily infected.
• Pancreatic pseudocyst: distinct from the above; a fluid collection without significant necrotic debris, also typically forming after 4 weeks.

True "pancreatic abscess" (a discrete, well-circumscribed collection of pus with minimal necrotic debris) is now a less commonly used term, having been largely superseded by the more precise revised Atlanta classification terminology above.

Persistent or worsening abdominal pain, fever, and failure to improve (or secondary deterioration after initial improvement) in a patient with known or recent severe acute pancreatitis should prompt suspicion of a local complication.

Infected necrosis specifically presents with new or persistent fever, worsening leukocytosis, and clinical sepsis, typically developing in the second to fourth week of the illness course, though it can occur earlier or later.

Contrast-enhanced CT characterizes the collection (fluid versus necrotic content, degree of organization/wall formation) and is the primary imaging modality; MRI offers superior characterization of necrotic debris content where the distinction is unclear on CT.

Infection is confirmed by the presence of gas within the collection on imaging (highly suggestive, from gas-forming organisms) or by image-guided fine needle aspiration with Gram stain and culture where the diagnosis is not clear from imaging and clinical picture alone. Routine aspiration of all collections is not required if gas is present or the clinical picture is unambiguous.

• Sterile (non-infected) necrosis or pseudocyst: managed conservatively where possible, since intervention is reserved for symptomatic collections (pain, gastric outlet or biliary obstruction, infection) or continued growth, rather than for the presence of a collection alone. Many sterile collections resolve spontaneously over weeks to months.
• Infected pancreatic necrosis: the modern standard is a "step-up" approach, starting with percutaneous or endoscopic (transgastric) drainage as the first intervention, escalating to minimally invasive or open necrosectomy only if drainage alone is insufficient.
• There is clear evidence that this staged, minimally invasive-first strategy reduces mortality and major complications compared with early open surgical necrosectomy.
• Antibiotics: empirical broad-spectrum IV antibiotics with good pancreatic tissue penetration (e.g. a carbapenem, or piperacillin-tazobactam) are started once infection is confirmed or strongly suspected, rationalized per culture results from drainage. Prophylactic antibiotics for sterile necrosis are not recommended, given lack of proven benefit and antimicrobial stewardship concerns.
• Timing: intervention for infected necrosis is, where the patient's condition allows, delayed until walled-off necrosis has formed (generally 4 weeks), given improved outcomes and reduced complication rates compared with earlier intervention. Earlier action is taken if the patient's clinical deterioration mandates it.
• Nutritional support (enteral, as detailed in the Pancreatitis entry) continues throughout

Referral: hepatobiliary/pancreatic surgery and interventional radiology or gastroenterology (for endoscopic drainage) as a multidisciplinary team for any local complication requiring intervention.