The term "necrotizing fasciitis'' was first used by Wilson in 1952 to describe bacterial infection producing necrosis of the fascia and subcutaneous tissue with sparing of the underlying muscle. Over half of these infections occur on the perineum, where they are called Fournier's gangrene (35). Common recent terminology that is less specific but includes serious destructive necrotizing infection is that of deep tissue necrotizing infection. These infections share common causes and treatment. The disease most often begins with a streptococcal infection in a breach in the skin in an immunosuppressed or diabetic patient, and perforating vessels are destroyed as the decomposition progresses, producing overlying ischemic necrosis. With the destruction of vessels, antibiotics cannot be delivered to the center of the necrotic and infected areas. The infection often becomes polymicrobial, with gram-negative organisms and anaerobic bacteria frequently playing a role. Gas-producing bacteria are fairly common, producing ''gas gangrene.''
The mortality rates of necrotizing fasciitis range from 6% to 76%. Mortality rates increase with delayed diagnosis and delayed surgical debridement. On the vulva and perineum, the infection may follow trivial injury such as a vulvar biopsy or folliculitis. However, it is more often seen after episiotomy, vulvar surgery, or vulvar abscess formation. Immunocompromised conditions such as advanced age, diabetes mellitus, chronic renal failure, cancer, and illicit drug use are risk factors for this disease process. Classic diagnostic signs are not always present.
Early clinical signs and symptoms include poorly demarcated areas of intense skin pain and pallor. Blister or bulla formation represents the beginning of critical skin ischemia. Later signs include hemorrhagic bullae, skin anesthesia from nerve
Figure 13 (See color insert) Necrotizing fasciitis is characterized by hemorrhagic bullae because of ischemia from underlying infection that has destroyed the cutaneous vascular supply; resulting ulceration and hemorrhage can be seen in this patient who is in the healing phase.
damage, and skin gangrene (Fig. 13). Tissue crepitus may be palpable. Systemic manifestations may include high fever, hypotension, multiorgan failure, and systemic shock. Symptoms usually develop within hours or several days with rapid progression. Histologically, the bacteria proliferate within the superficial fascia and tissue necrosis is present. Enzymes and toxins produced allow for superficial spread of the bacteria. Angiothrombotic microbial invasion and liquefaction necrosis ensue.
The differential diagnosis includes cellulitis, which can sometimes be indistinguishable, brown recluse spider bite, and bullous pyoderma gangrenosum. A plain radiograph, computed tomography (CT), ultrasound, or magnetic resonance imaging may be helpful in diagnosis. Plain radiographs can show soft-tissue air in some patients. On CT, findings include deep fascial thickening, enhancement, and fluid and gas in the soft-tissue planes. Fine-needle aspiration or incisional biopsy may also be helpful for diagnosis when necrotizing fasciitis is suspected. A stab incision yields decomposed necrotic tissue rather than the inflamed and edematous tissue of cellu-litis. During surgery, findings include a lack of tissue resistance, lack of bleeding of the fascia during dissection, and foul-smelling dishwater-colored pus. Laboratory values include an elevated white cell count, glucose, urea, and creatinine. Hypoalbu-minemia, acidosis, and an altered coagulation profile may also be present.
The most important aspect of management is early diagnosis, antibiotics, and aggressive debridement (36). Methicillin-resistant S. aureus has been reported in community-acquired necrotizing fasciitis, so that this should be considered in the choice of an antibiotic (37). Hyperbaric oxygen has been suggested by some, but this has not been shown to be of use in other series (38). Polyspecific immunoglobulin may be beneficial adjunctive therapy (39). Management requires early diagnosis, immediate resuscitation, aggressive and repeated surgical debridement, hyperbaric oxygen, and broad-spectrum antibiotics (Table 12).
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