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Phlegmon: Causes, Symptoms, Treatment, Classification, Diagnosis

What is Phlegmon?

Phlegmon is a medical condition where there is acute diffuse inflammation of the adipose tissue which spreads with formation of purulent exudate. Inflammation of Phlegmon can also spread to cellular spaces and also involve tendons and muscles. Bacterial infection may be associated with this condition, however, the word ‘phlegmon’ is derived from Greek which means inflammation and it refers to a inflammatory mass which is walled-off without bacterial infection and which can be palpated upon physical examination. Some of the examples of phlegmon is diverticulitis where the patient experiences abdominal tenderness in the left lower-quadrant. CT scan confirms the diagnosis. Spondylodiscitis is one more example of phlegmon which affects the spine and where there is loss of disc height and endplate destruction. Phlegmon, when it affects the spine, can be a localized abscess in the sub-ligamentous, epidural or paraspinous spaces or can be a diffuse enhancement.

What is Phlegmon?

Classification of Phlegmon

  1. Classification of Phlegmon depending on its clinical course:

    • Acute Phlegmon.
    • Subacute Phlegmon.
  2. Classification of Phlegmon depending on its severity:

    • Mild Phlegmon.
    • Average Phlegmon.
    • Severe Phlegmon where it spreads to other locations.
  3. Classification of Phlegmon depending on its location:

    • Superficial Phlegmon
    • Cutaneous Phlegmon.
    • Subcutaneous Phlegmon.
    • Interstitial tissue Phlegmon.
    • intramuscular Phlegmon
    • Deep Phlegmon.
    • Mediastinal Phlegmon.
    • Retroperitoneal Phlegmon.
  4. Classification of Phlegmon depending on its Cause:

    • Single Phlegmon.
    • Mix Phlegmon which can consist of spore and non-spore forming anaerobes.
  5. Classification of Phlegmon depending on its Pathogenesis:

    • Per continuitatem where it develops from neighboring tissues.
    • Hematogenous.
    • Odontogenous.
  6. Classification of Phlegmon depending on its Exudative Character:

    • Purulent phlegmon.
    • Purulent-hemorrhagic phlegmon.
    • Putrefactive phlegmon.
  7. Classification of Phlegmon depending on its Complications:

    • Phlegmon with complications where the patient has difficulties with ingestion, mastication and speech. Problems with respiratory and cardiovascular system, lymphadenitis and peritonitis. There can be loss of consciousness in severe cases.
    • Phlegmon without complications.

What are the Causes of Phlegmon?

Phlegmon is commonly caused by bacteria: non-spore and spore forming anaerobes, streptococci etc. Immunity strength of the patient and virulence of bacteria are other factors which affect the development of phlegmon.

What are the Symptoms of Phlegmon?

Symptoms of Systemic Infection from Phlegmon consist of:

Symptoms of Inflammation from Phlegmon consist of:

  • Localized pain.
  • Hyperemia or skin redness.
  • Increased local temperature.
  • Painful tissue swelling which can be non-clear bordered or clear or bordered (tumor).
  • Decreased function of the affected body part.

Phlegmon which is noninfectious can be found in acute pancreatitis which occurs in Systemic Lupus Erythematosus (SLE). The immunosuppressive medications used to treat SLE and immunosuppressive aspects of SLE subdue the signs of infection from Phlegmon.

Note of importance here is the degree of patient’s condition with phlegmon is directly proportional to the degree of intoxication level. The more severe the condition, the greater will be the purulent intoxication level.

How is Phlegmon Diagnosed?

Diagnosis of Phlegmon is made based on the following:

  • Patient’s symptoms, complaints and physical exam.
  • Patient’s previous medical history.
  • Palpation during physical exam.
  • Blood test including CBC is done.
  • Urine test, which will detect bacteria in urine in case of Phlegmon.
  • Imaging tests such as x-ray, ultrasound, CT scan and MRI scan.

How is Phlegmon Treated?

  • The main aim of treatment of Phlegmon is removing the cause of the phlegmonous process so that treatment is achieved and recurrence can be prevented.
  • Conservative treatment consisting of antibiotics is started if the Phlegmon is mild and inflammation is present without any signs of infiltrates.
  • In severe cases, surgery is needed to drain the Phlegmon, to excise dead tissues and to prevent further spread of infection. Surgery is done under general anesthesia where the cavity which contains the phlegmonous process is cleaned with antibiotic and antiseptic solutions and the dead tissue is removed. Intravenous antibiotics are given to the patient in post-operative period.
  • During surgery for removal of phlegmon, it is important to avoid spreading of pus, to avoid damaging nerves and to take into consideration the aesthetic value of the operating site, especially if the phlegmmonous process is on the face.


Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:July 17, 2023

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