It is a descriptive term which may be used for inflammation related to a bacterial infection or non-infectious causes (e.g. pancreatitis).
As with any form of inflammation, phlegmon presents with inflammatory signs dolor (localized pain), calor (increase local tissue temperature), rubor (skin redness/hyperemia), tumor (either clear or non-clear bordered tissue swelling), functio laesa (diminish affected function).
There may be systemic signs of infection, such as fever, general fatigue, chills, sweating, headache, loss of appetite.
In modern medicine, phlegmon is mostly used descriptively in the fields of surgery/surgical pathology and medical imaging.
The ultrasound and CT imaging findings of phlegmon are those of focal tissue edema, with no loculated fluid collection to suggest the formation of an abscess.