A phlegmon is a serious infection characterized by inflammation that spreads through soft tissue or an organ’s internal structure. Because initial symptoms can appear similar to localized infections, it is often confused with them. Understanding what distinguishes a phlegmon from a contained infection is important for recognizing its severity. This spreading inflammation requires prompt medical attention to prevent systemic complications.
Defining Phlegmon and Its Nature
A phlegmon is an acute, diffuse, and non-localized inflammation of soft tissue, organ parenchyma, or connective tissue. Unlike infections the body attempts to wall off, a phlegmon lacks a defined fibrous capsule or boundary. The inflammation spreads along tissue planes and between muscle fibers, defining it as a diffuse process. This characteristic fundamentally differentiates it from an abscess.
An abscess is a collection of pus contained within a distinct, encapsulated wall of tissue. The immune system forms this wall to isolate the infection, making the abscess easier to treat with simple drainage. Conversely, a phlegmon is an infiltrating process that rapidly moves through spaces. This makes it difficult to drain effectively without surgical debridement of the inflamed tissue. If left untreated, a phlegmon may progress to form a contained abscess or spread widely, causing severe systemic illness.
Common Causes and Locations
Phlegmons are caused by bacterial pathogens that invade soft tissue, often following a break in the skin or spread from a nearby infection site. Common bacterial culprits include Group A Streptococcus and Staphylococcus aureus, as well as mixed aerobic and anaerobic organisms. The specific type of bacteria often relates to the anatomical site, which dictates the required antibiotic regimen.
These spreading infections can occur anywhere, but certain locations are more frequently affected or carry higher risk. Odontogenic (dental) infections are a common source, leading to phlegmons in the face or neck. Deep soft tissues of the neck, such as in Ludwig’s angina, are concerning due to the risk of airway compromise. Abdominal phlegmons frequently arise as a complication of conditions like appendicitis or diverticulitis, where inflammation spreads into the surrounding tissue.
Recognizing the Signs
A person experiencing a phlegmon exhibits both localized and systemic signs of severe infection. Locally, there is severe and diffuse pain that is not confined to a single point. This pain is accompanied by classic signs of inflammation: redness (rubor), warmth (calor), and noticeable swelling (tumor) over the affected area.
The inflamed area may feel firm and indurated to the touch, indicating tissue infiltration, rather than the fluctuant feel of a contained abscess. Systemic symptoms reflect the body’s response to the widespread infection and include fever, chills, and general malaise. While recognizing these signs is important, a definitive diagnosis requires medical assessment and imaging.
Diagnosis and Treatment
Diagnosing a phlegmon begins with a thorough clinical assessment, noting the diffuse nature of the pain and swelling. Blood tests confirm a systemic infection, often revealing an elevated white blood cell count and increased inflammatory markers. Imaging studies are then performed to visualize the tissue and confirm the absence of a defined pocket of pus.
Computed tomography (CT) or magnetic resonance imaging (MRI) scans are frequently used. These scans show focal tissue edema and non-loculated fluid, lacking the enhancing rim seen in an abscess. Treatment protocols for a phlegmon are aggressive due to the infection’s potential for rapid spread. The standard course involves the immediate administration of broad-spectrum intravenous antibiotics to cover likely aerobic and anaerobic pathogens.
Surgical intervention is often necessary, especially if the infection does not respond quickly to antibiotics or is in a high-risk location. This may involve prompt surgical debridement to remove infected and dead tissue or aggressive drainage procedures. The goal of this combined approach is to contain the diffuse infection, eliminate the bacterial source, and prevent spread that could lead to widespread tissue destruction or systemic complications like sepsis.