Phlegmon: Definition, Classification, Causes, Symptoms, Diagnosis, Treatment and Outlook

Basically, we are talking about a pus sac in a tooth caused by an infection.

Phlegmon is a medical condition in which there is an acute diffuse inflammation of the adipose tissue that spreads with the formation of a purulent exudate.

The inflammation of a phlegmon can also spread to the cell spaces and also involve the tendons and muscles.

Bacterial infection may be associated with this condition, however the word “Phlegmon” is derived from the Greek, meaning inflammation, and refers to an inflammatory mass that is walled in without bacterial infection and can be felt on physical examination.

Some of the examples of phlegmon are diverticulitis in which the patient experiences abdominal tenderness in the left lower quadrant.

Computed tomography confirms the diagnosis. Spondylodiscitis is one more example of phlegmon that affects the spine and where there is loss of disc height and destruction of the end plate.

Phlegmon, when it affects the spinal column, can be an abscess located in the sub-ligamentous, epidural or paraspinous spaces or it can be a diffuse enhancement.

A phlegmon spreads just under the skin in cases of superficial phlegmon or within the body, being located near an organ which is called deep phlegmon.

A phlegmon can affect internal organs such as the appendix, or it can be under the skin of the fingers or on the tonsils.

The soft tissue or connective tissue where a phlegmon forms, is a tissue rich in fibers that protects or supports the organs and tissues of the body.

This lesion is infectious in origin, the phlegmons destroy the tissues they affect and can spread, although there are usually microabscesses, and it can cause tissue necrosis.

Phlegmon can spread quickly, and in some cases, it can be life-threatening.


A phlegmon can be classified based on:

Its clinical course

  • Acute phlegmon.
  • Subacute phlegmon.

Its severity

  • Ad.
  • Flemón light.
  • Middle phlegmon.
  • Severe phlegmon where it spreads to other places.

Your location

  • Superficial phlegmon
  • Cutaneous phlegmon.
  • Subcutaneous phlegmon.
  • Phlegmon of interstitial tissue.
  • Flemón intramuscular
  • Deep phlegmon.
  • Mediastinal phlegmon.
  • Flemón retroperitoneal.

Its exudative character

  • Purulent phlegmon.
  • Purulent-hemorrhagic phlegmon.
  • Putrid phlegmon.

Its complications

  • Complicated phlegmon where the patient has difficulties with swallowing, chewing, and speaking. Problems with the respiratory and cardiovascular system, lymphadenitis and peritonitis. There may be loss of consciousness in severe cases.
  • Uncomplicated phlegmon.

Phlegmon and abscess

The differences between a phlegmon and an abscess are as follows:

  • A phlegmon is unlimited and can continue to spread diffusely throughout the connective tissue and muscle fiber, whereas an abscess is walled and confined to the area of ​​infection.
  • Abscess and phlegmon can be difficult to distinguish in some cases. Sometimes phlegmon occurs when infected material within an abscess breaks loose from its self-containment and spreads.
  • Usually an abscess can be drained of its infected fluid, but a Phlegmon cannot be drained easily.

Causes of a phlegmon

Phlegmon is commonly caused by bacteria most often group A streptococci or Staphylococcus aureus.

Resistance to the immunity of the patient and the virulence of bacteria are other factors that affect the development of Phlegmon.

Bacteria can enter through a scratch, insect bite, or injury to form phlegmon just under the skin of your fingers or feet.

Bacteria in the mouth can cause phlegmon or oral abscess, especially after dental surgery.

Bacteria can also stick to the wall of an internal organ such as the stomach wall or appendix and form phlegmon.

People with compromised immune systems can be especially vulnerable to the formation of Phlegmons.

Symptoms of a phlegmon

The symptoms of a Phlegmon vary, depending on the location and severity of the infection. If left untreated, an infection can spread to deeper tissue and disable the affected limb or area.

The symptoms of inflammation of a Phlegmon consist of:

  • Localized pain
  • Hyperemia or redness of the skin.
  • Increase in body temperature.
  • Painful swelling in the tissue that may be unclear, edged, clear, or edged (tumor).
  • Decreased function of the affected body part.

Symptoms of systemic phlegmon infection include:

  • Fever or increased body temperature
  • Fatigue.
  • Perspiration.
  • Increased thirst.
  • A cold.
  • Loss of appetite
  • Headache.

Phlegmon that is not infectious can be found in acute pancreatitis that occurs in systemic lupus erythematosus.

Immunosuppressive medications used to treat systemic lupus erythematosus and the immunosuppressive aspects of systemic lupus erythematosus attenuate the signs of Phlegmon infection.

Flexor sheath phlegmon is the most common. It results in inflammation of the finger, which is red, hot, extremely painful, swollen, and locked in the folded position.

Peritonsillar phlegmon, there is a significant localized pain groove on one side and can radiate to the ear and a locking gag (lockjaw) with swallowing difficulties and a high fever of 39 ° to 40 ° C.

There is also a deviated swollen uvula and this makes swallowing almost impossible. The voice is usually altered (dysphonia) and the submaxillary nodes are very sensitive.


The symptoms of phlegmon of the skin are visible but internal phlegmons are more difficult to diagnose. The doctor will look for lumps or tenderness in the area of ​​pain.

The diagnosis of Phlegmon is made based on the following:

  • Previous medical history of the patient.
  • Palpation during physical examination.
  • Blood tests including complete blood count are done.
  • Urine test, which will detect bacteria in the urine in case of Phlegmon.
  • Imaging tests, such as X-rays, ultrasound, CT scan, and MRI.

To distinguish between cellulitis, abscess, and phlegmon, your doctor may use intravenous gadolinium in MRI imaging to show the profile of an abscess “wall” compared to phlegmon.

Treatment of phlegmon

The main goal of Phlegmon treatment is to eliminate the cause of the phlegmonic process so that treatment can be achieved and recurrence can be prevented.

Treatment for phlegmon depends on the location and severity of the infection. In general, treatment involves both antibiotics and surgery.

Phlegmon of the skin, if it is minor, can be treated with oral antibiotics. But surgery may be needed to clean the dead tissue from the area and prevent the infection from spreading.

Oral phlegmon can spread quickly and can be life-threatening. Early aggressive use of antibiotics in conjunction with intubation (placement of a breathing tube into the trachea) is recommended.

Surgery is also recommended as soon as possible to drain the area and stop the spread of the infection.

Before antibiotics were developed, 50 percent of people with phlegmon in the mouth area died.

Flexor sheath phlegmon should be treated urgently. It consists of surgically removing the tissues that have been destroyed under general anesthesia.

The affected area will then be cleaned and the finger immobilized. Antibiotic therapy is also given to eradicate the causative bacteria.

Then rehabilitation begins and healing occurs after two weeks.

With delayed treatment, flexor sheath phlegmon can cause definitive blockage of the finger in flexion, bent toward the palm.

Peritonsillar treatment is also treated urgently and involves incision and drainage of the phlegmon (under local or general anesthesia). Antibiotics are given intravenously.

Peritonsillar phlegmons, even if properly treated, have systemic relapses. This is what motivates the removal of the tonsils two months after treatment of the infection.

The surgery is performed under general anesthesia where the cavity containing the phlegmonic process is cleaned with antibiotics and antiseptic solutions and the dead tissue is removed. Antibiotics are administered intravenously to the patient in the postoperative period.

During surgery for the removal of phlegmon, it is important to avoid the spread of pus, avoid damaging the nerves, and take into account the aesthetic value of the operation site, especially if the phlegmon process is on the face.


The outlook for phlegmon depends on the severity of the infection and the area infected. Immediate medical attention is always necessary.

Antibiotics are generally required to clear the infection. Surgery is often necessary, but in some cases conservative management may be enough to resolve the phlegmon. With treatment, the overall outlook for phlegmon is good.