Cellulitis
Updates to Article Attributes
Cellulitis is an acute infection of the dermis and subcutaneous tissues. It results in pain, erythema, oedema, and warmth. Since the epidermis is not involved, cellulitis is not transmitted by person-to-person contact.
Clinical presentation
Cellulitis can affect any region of the body, and commonly affects a lower limb. Clinical presentations include skin erythema without a well-defined border, increased skin temperature, swelling of the affected area, and regional lymphadenopathy and lymphangitis. Additionally, systemic features such as fevers and rigors may also be present.
Complications
If the infection spreads to deeper tissues, complications can occur, such as soft-tissue abscess, infectious myositis, necrotising fasciitis, or osteomyelitis. Special consideration should be given to geriatric patients, in whom cellulitis of the lower extremities is more likely to develop into thrombophlebitis.
Pathology
Cellulitis occurs after disruption of the skin and invasion of the subcutaneous tissues by microorganisms that may be skin flora, such as Staphylococcus aureus, or other bacteria. Patients with peripheral vascular disease or diabetes mellitus are particularly susceptible to cellulitis since minor injuries to the skin or cracked skin in the feet or toes can serve as a point of entry for infection.
Radiographic features
Ultrasound
Ultrasound is usually the first investigation to evaluate a clinical suspicion of cellulitis. Normally the subcutaneous tissue is hypoechoic with few hyperechoic strands (representing connective tissue). Above this, there is a narrow, relatively hyperechoic epidermal-dermal layer. Muscular fascia lie deep to the subcutaneous layer.
- sonographic hallmarks of cellulitis include abnormal echogenicity and increased thickness of the dermis with indistinct "haziness" and increased echogenicity of the subcutaneous tissue
- it is often helpful to compare the area in question to the (presumably normal) contralateral side
- progressive accumulation of oedema in the subcutaneous tissue appears as branching, anechoic striations which impart a lobulated ("cobble-stone" appearance
")- also present in other oedematous states
- presence of thickened and abnormally echogenic overlying skin will favor cellulitis over edema
- linear anechoic bands of fluid deep to the subcutaneous layer favor lymphoedema
CT
CT is used to accurately differentiate between superficial cellulitis and deep cellulitis.
In uncomplicated cellulitis, CT demonstrates skin thickening, septation of the subcutaneous fat, and thickening of the underlying superficial fascia. If the infection spreads to deeper tissues, soft-tissue abscess, infectious myositis, necrotising fasciitis, and osteomyelitis can all be detected with CT.
Treatment and prognosis
Uncomplicated cellulitis is usually treated conservatively with antibiotics and locally supportive measures.
Differential diagnosis
Clinical differential diagnoses include:
- erysipelas
- deep vein thrombosis
- myriad of non-infective erythematous rashes
See also
-<li>progressive accumulation of oedema in the subcutaneous tissue appears as branching, anechoic striations which impart a lobulated ("cobble-stone" appearance "<ul>- +<li>progressive accumulation of oedema in the subcutaneous tissue appears as branching, anechoic striations which impart a lobulated ("cobble-stone" appearance)<ul>
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