Cellulitis
Summary
Cellulitis is a common bacterial skin infection that is often caused by the Staphylococcus or Streptococcus bacteria. Patients will present with pain, redness and swelling in a specific area of skin because of the inflammation caused by the infection. Without treatment, the bacterial infection can spread to other parts of the body and result in dizziness, weakness, and chills. Physical exams may be remarkable for cuts or other wounds that serve as an entry point into the body for the bacteria. Imaging such as ultrasound and CT may be used to assess the extent of the infection, and will reveal abnormal thickness of the skin layers. In severe cases of cellulitis, a CT will reveal damage to the underlying soft tissue. Cellulitis is treated with oral or intravenous (IV) antibiotics. In order to decrease the risk of cellulitis, especially in the lower limbs, patients can regularly hydrate, exercise, and moisturize.
Clinical Presentation
Cellulitis commonly occurs when bacteria enters the skin and underlying tissues through breaks in the skin. As a result, the bacterial infection is initially localized to a particular area. Patients will present with redness and swelling in the area of skin affected, often the lower legs. In some individuals the infected area may become filled with pus. If the bacterial infection spreads throughout the body, patients may experience more severe symptoms of sepsis such as dizziness, weakness, and chills.
Physical Exam
The bacteria that cause cellulitis often invade the body through breaks in the skin. Therefore, a physical exam may reveal cracks, cuts, puncture wounds, or bite wounds. In uncomplicated cellulitis, the affected area may be painful to touch. The involved skin is often red and swollen. However, patients with cellulitis that affects the lower legs are often still able to walk.
Imaging
Cellulitis is diagnosed through patient history, and physical examination. Blood work, and culture of any pus-filled wounds are sometimes used to assess the severity of the cellulitis. Imaging can be used to determine the extent of cellulitis, as well as assess complications of the infections.
Ultrasound
Ultrasound is used to evaluate the skin layers at the site of the cellulitis. In the setting of cellulitis, the dermis (the second layer of skin) will be thicker than normal. Additionally, the subcutaneous layer, which is just below the dermis, will appear lighter (more hyperechoic) on ultrasound.
A doppler ultrasound can assess for blood clots associated with the cellulitis infection. Since cellulitis commonly occurs in the lower legs, a doppler ultrasound can reveal a condition known as deep vein thrombosis.
CT
A CT can reveal thickened layers of skin in cellulitis. In more severe cases, CT may be used to diagnose complications of cellulitis, such as osteomyelitis, soft tissue infections (i.e. necrotizing fasciitis), and abscesses.
Treatment
The first line of treatment for cellulitis is administration of appropriate antibiotics which is often given orally, although intravenously (IV) administration may be necessary in more severe cases. While Staphylococcus and Streptococcus are the two most common bacteria associated with cellulitis, there are other types of bacteria that can cause this condition. Therefore, in complicated cases of cellulitis, a bacterial culture is performed to determine the type of bacteria involved. An appropriate antibiotic regimen is selected based on the traits and resistance patterns of the specific bacteria. The symptoms of cellulitis, such as pain and swelling, can also be treated with rest; elevation of the affected limb; and over-the-counter pain relievers.
Edited March 21st, 2021