Clavien et al listed criteria for distinguishing edema from phlegmon on CT images of the pancreas. This can help identify patients with severe acute pancreatitis. The authors are from the University of Geneva in Switzerland.
NOTE: Phlegmon is a nonspecific term that used less often today. Pancreatic necrosis is more commonly used.
Features in the Pancreas
Normal
Edema
Pancreatic Phlegmon
swelling
none
slight
significant
homogeneity
homogenous
homogenous
heterogenous
contrast enhancement
normal
decreased
avascular areas
Features of an Extrapancreatic Lesion
Normal
Edema
Extrapancreatic Phlegmon
margin
sharp
sharp
ill-defined
homogeneity
homogenous
homogenous
heterogenous
contrast enhancement
normal
none or decreased
possible wall enhancement
extent
normal
within anatomic barriers
extends beyond anatomic barriers
fatty tissue
normal
slightly elevated densities (-50 to +10 Hounsfield units)
replaced by fluid collections (+20 to +40 Hounsfield units)
Interpretation:
• If the diagnosis is in doubt, the lesion is classified as a phlegmon (page 458).
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