Cellulitis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Cellulitis is a skin infection that causes inflammation of the connective tissue underlying the skin. Cellulitis can be caused by the infection of normal skin flora or by exogenous bacteria, and often occurs in places where the skin has previously been broken: cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, or sites of intravenous catheter insertion. Cellulitis mainly affects the top layer of skin, but it may also affect the tissues underlying the skin. Skin on the face or lower legs is most commonly affected, although cellulitis can occur on any part of the body. This inflammation can disseminate throughout the body if it spreads to the lymph nodes and bloodstream.
This condition is unrelated to cellulite, a cosmetic condition featuring dimpling of the skin.
Pathophysiology
Microorganisms gain initial access into the layers of the skin through the discontinuities and cuts in the skin. The body responds to these microbes as foreign bodies and their detection sets off an inflammatory response. The inflammatory response leads to redness, swelling, pain and itching of the area involved.
Causes
The most common causative microbes of cellulitis are Streptococci and Staphylococcus aureus. Another causative microbe is the bacteria Pasturella multocida.
Differentiating Cellulitis from other Diseases
Cellulitis should be distinguished from thrombophlebitis, contact dermatitis, insect stings, drug reactions, and arthritis.
Risk Factors
The elderly, patients with impaired circulation to and drainage from the extremities, and those with weakened immune systems are especially vulnerable to contracting cellulitis.
Natural History, Complications and Prognosis
Cellulitis develops between 1-5 days after the initial bacterial infection. The development mainly depends on the type of bacteria involved in the infection. Bites from animals like dogs or cats mostly cause the infection by transferring the bacteria Pasturella multocida. This bacteria has a very short incubation period of about 4-24 hours.
Duration
In many cases, cellulitis takes less than a week to disappear with antibiotic therapy. However, it can take months to resolve completely in more serious cases, and can result in severe debility or even death if untreated. If it is not properly cured, cellulitis may appear to improve but can resurface again even after months and years of inactivity. The duration of the disease depends upon the general condition of the individual. People with uncontrolled diabetes, HIV and other immunodeficiency conditions may need a long time to cure cellulitis even with antibiotic treatment.
Cellulitis can be complicated by the development of sepsis, osteomyelitis, lymphangitis, endocarditis, meningitis, and gangrene. The prognosis of cellulitis is good provided the patient starts on an antibiotic treatment regimen.
Diagnosis
History and Symptoms
Cellulitis is most often a clinical diagnosis, and local cultures do not always identify the causative organism. Blood cultures are usually positive only if the patient develops generalized sepsis. Conditions that may resemble cellulitis include deep vein thrombosis, and stasis dermatitis.
Physical Examination
Cellulitis is mainly a clinical diagnosis based upon a patient's history, symptoms, and physical examination. Physical exam indications such as warmthness of the affected area, erythema, and swelling of nearby nodes can clinch the diagnosis.
Laboratory Findings
With changing trends in medicine, recommended lab investigations are changing. Blood cultures and blood counts are the mainstay for the treatment and prognosis of cellulitis. Other blood tests such as ESR and CRP assist in prognosis. Levels of ESR and CRP taken at a patient's admission may predict the severity and duration of hospitalization. [1]
Imaging
Imaging may be considered when bone involvement in suspected and if a foreign body in-situ is one of the differential.
CT
In cases of deep abscess or occult abscess, in cases of orbital cellulitis to differentiate pre/post septal CT scan is quite useful tool.
MRI
Soft tissue involvement is seen in cases of untreated or in rapidly spreading progressing cellulitis. MRI can be of great value in such cases.
Ultrasound
Ultrasound can be used in cases of occult abscesses. It useful in aspiration of pus in children and reduces hospital stay.
Treatment
Medical Therapy
Typically a combination of intravenous and oral antibiotics are administered for the treatment of cellulitis. Bed rest and elevation of the affected limbs are recommended to accompany the antibiotic treatment. In patients with edema of the extremities, compressive stockings may really aid in treating the fluid accumulation. Small abscesses surrounding the affected tissue can be treated with a simple incision and drainage of the fluid. It is advised to drink plenty of fluids during your treatment and recovery.
Primary Prevention
Good hygiene and good wound care lower the risk of cellulitis. Any wounds should be cleaned and dressed appropriately. Changing bandages daily or when they become wet or dirty will reduce the risk of contracting cellulitis. Medical advice should be sought for any wounds which are deep, dirty or if there is any concern about retained foreign bodies.
References
- ↑ Lazzarini L, Conti E, Tositti G, de Lalla F (2005). "Erysipelas and cellulitis: clinical and microbiological spectrum in an Italian tertiary care hospital". J Infect. 51 (5): 383–9. doi:10.1016/j.jinf.2004.12.010. PMID 16321649.