Pancreatic Infected Necrosis and Abscess

Brooke R. Jeffrey, MD

Michael P. Federle, MD, FACR

Key Facts

Imaging

Infected pseudocyst: Often has same appearance as noninfected pseudocyst
Abscess: Well-circumscribed fluid collection, round, oval, or irregular ± gas
Necrosis: Focal, segmental, or involving entire pancreas; poorly marginated

Top Differential Diagnoses

Sterile necrosis of pancreas (necrotizing pancreatitis)
Pancreatic ductal carcinoma
Pancreatic pseudocyst
Mucinous cystic pancreatic tumor

Clinical Issues

Infected pseudocyst: Patients may be febrile but not very ill
Abscess: Patients are moderately ill
- Develops late in course of acute pancreatitis (usually after 4 weeks)
Infected necrosis: Patients are very ill, “toxic”
- Develops early (< 4 weeks) in course of acute necrotizing pancreatitis
- CT/US-guided needle aspiration needed to establish diagnosis

Diagnostic Checklist

Distinguish among infected pseudocyst, abscess, and infected pancreatic necrosis
- Infected pseudocyst: Percutaneous catheter drainage; quick recovery
- Abscess: Percutaneous or surgical drainage, prolonged illness
- Infected pancreatic necrosis: Surgical debridement; often repeated; high morbidity and mortality

(Left) Axial CECT demonstrates multiple gas bubbles

within infected fluid collection in the lesser sac. (Right) Axial CECT shows extensive necrosis of the body of the pancreas with only a small residual area of enhancing parenchyma

. Note the multiple gas bubbles

and air-fluid level

within the infected collection. There is an enlarged gastroepiploic collateral vein

secondary to splenic vein thrombosis.

(Left) Axial CECT shows extensive necrosis with nonenhancement of the body of the pancreas

. (Right) Postoperative axial CECT in the same patient shows a large-bore drainage catheter

in the bed of the necrotic pancreas. Despite the lack of gas bubbles on CECT, the patient underwent surgical debridement due to septicemia. Operative cultures grew multiple coliform bacteria.

TERMINOLOGY

Definitions

Infected pseudocyst: Bacterial colonization of pseudocyst
Pancreatic abscess: Circumscribed collection of pus, in or near pancreas, containing little or no pancreatic necrosis
- Arises as consequence of acute pancreatitis or pancreatic trauma
Infected necrosis: Secondary infection of necrotic pancreatic tissue in setting of acute pancreatitis

IMAGING

General Features

Best diagnostic clue
- Infected pseudocyst
  - Spherical “cyst” with enhancing wall ± gas in lumen
- Abscess
  - Localized near-water density mass adjacent to pancreas ± gas bubbles
- Infected necrosis
  - Poorly marginated, nonenhancing lesion in pancreas ± gas bubbles
Location
- Inside or adjacent to pancreas
Size
- Varies
- Could be single or multiple
Morphology
- Abscess
  - Well-circumscribed fluid collection: Round, oval, or irregular
  - Relatively homogeneous contents
- Infected necrosis
  - Focal, segmental, or involving entire pancreas
  - Poorly marginated