Necrotizing fasciitis is an uncommon, severe infection involving skin, subcutaneous fat, muscle sheath (fascia), and muscle. It may result from bacterial infection through a break in the skin or surgical wound infection. The bacteria begin to grow and release toxins that directly kill tissue, interfere with the blood flow to the tissue, digest materials in the tissue, which then allows the bacteria to spread rapidly, and/or cause widespread systemic effects such as shock. There are two major types of necrotizing fasciitis: Type I results from mixed anaerobic and facultative bacteria, including Enterobacteriaceae and non-group A streptococci. In Type II, group A streptococci is isolated alone or with staphylococci. Of the anaerobes, Bacterioides spp and Peptostreptococcus spp are commonly found. Gas forming bacteria may produce crepitance, and the infection must be differentiated by smear from the rarer, pure clostridial gas gangrene.
Necrotizing fasciitis can affect any part of the body but is most common on the extremities, particularly the legs. Other sites are the abdominal wall, perianal and groin areas, and postoperative wounds. Inadequate drainage of a perirectal abscess, usually under local anesthesia in the emergency room rather than in the controlled situation of the main operating room, puts the patient at particular risk. Necrotizing fasciitis from intestinal sources may occur in the lower extremity (extension along the psoas muscle), as well as in the groin or abdominal wall.
Despite advances in antibiotics and infection control practices, necrotizing fasciitis is still a potentially lethal disease. The mortality rate of necrotizing fasciitis ranges from 9 to 74% overall. Risk factors for incidence and poor outcome include trauma and surgery, solid-organ transplantation, diabetes mellitus, advanced age, alcoholism, and arteriosclerosis.
Diagnosis and Treatment
Presenting signs typically include necrosis, edema, and cellulitis. Systemic symptoms may include fever, tachycardia, chills, nausea, dizziness, profound weakness and finally shock. Early clinical differentiation of necrotizing fasciitis from cellulitis may be difficult because the initial signs, including pain, edema, and erythema, are not distinctive. However, the presence of marked systemic toxicity out of proportion to the local findings should be the alert.
In patients in whom the diagnosis is clearly suspected, the quickest route to diagnosis is through surgical exploration or biopsy. Imaging studies may be helpful in monitoring clinical progress after surgical debridement when further surgery may be considered. Imaging studies may also be helpful in the diagnosis and management of necrotizing fasciitis in areas of the body where the process may be more inaccessible (e.g., retroperitoneal involvement) or where the infection may readily spread to other tissue compartments (e.g., cervical fasciitis spreading to the mediastinum, pleura, and pericardium).
Extremely powerful broad-spectrum or organism-specific intravenous antibiotics must be administered immediately. Aggressive, wide surgical debridement is the mainstay of treatment; early surgical debridement largely influences the prognosis. Repeated debridement and opening of all involved tissue planes is often necessary. Skin grafts may be required after the infection is cleared. If the infection is in a limb and cannot be contained or controlled, amputation of the limb may be necessary. Management of fluids and septic shock are also important. Hyperbaric oxygen therapy may or may not be effective-the results are inconclusive.
The prognosis depends on age, comorbidity, and the severity of the sepsis syndrome. Initial resuscitation involves controlling the hypotension and organ dysfunction associated with severe sepsis, and is usually dominated by a severe hypovolemia. Outcomes are extremely variable. The type of infecting organism, rate of spread, susceptibility to antibiotics, and how early the condition was diagnosed all contribute to the final outcome. Scarring and deformity are minimal outcomes for this type of disease. Fatalities can be high even with aggressive and advanced treatment and powerful antibiotics. Untreated, the infection invariably spreads and causes death.
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