2024/08/30 by Elizabeth J. Jones, Peter Drew · 2 voices
Medicine · #Streptococcal Infections and Treatments
paper · doi:10.1093/bjs/znae204
openalex publication_date 2024/08/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
Necrotizing fasciitis is a life-threatening soft-tissue infection The dominant features are rapidly progressive inflammation and necrosis of the deep fascia, subcutaneous fat, and skin, with associated systemic sepsis A delay in diagnosis increases mortality risk The benefits of imaging should be considered against the risks of a delay in treatment The mainstays of initial management are resuscitation, intravenous broad-spectrum antibiotics, and aggressive surgical debridement Necrotizing fasciitis (NF) is a life-threatening soft-tissue infection, requiring early recognition and urgent surgery if optimal outcomes are to be achieved. Its dominant features are rapidly progressive inflammation and necrosis of the deep fascia, subcutaneous fat, and skin, with associated systemic sepsis. NF is the most common infection in a spectrum of necrotizing soft-tissue infections which includes necrotizing myositis and cellulitis. Approximately 500 new cases of NF are reported annually in the UK1. NF can occur in any anatomical area; disease affecting the perineum or genitals is known as Fournier’s gangrene. NF is often attributable to the inoculation of bacteria into tissues via a traumatic or surgical wound. In certain areas of Asia, consumption of raw seafood and injuries from fish fins, leading to exposure to marine bacteria, such as Vibrio spp., are also major causes2,3. Haematogenous spread from a distant site may also occur4. In a minority of cases, the exact cause is never clearly identified. Co-morbidities that impair host defence mechanisms (e.g. diabetes mellitus, HIV/AIDS, steroid use, malnutrition, or intravenous drug use) predispose patients to NF5, while, in children, concurrent varicella infection is a risk factor6. NF can be classified according to the number and species of bacteria isolated. Type 1 (80% of cases) is polymicrobial, with an average of 2.8 organisms isolated per patient7. Gram-positive and Gram-negative aerobes are most commonly identified (see Table 1)5. Type 2 is monomicrobial, usually involving Gram-positive organisms, and type 3 involves clostridial species or other Gram-negative organisms. Type 4 is fungal in origin8. Bacteriological classification of necrotizing fasciitis Bacteriological classification of necrotizing fasciitis A delay in diagnosing NF is known to increase mortality risk9. In its early stages, NF may be indistinguishable from other soft-tissue infections, presenting with non-specific signs and symptoms (such as nausea, fever, diarrhoea, dizziness, or general malaise), alongside erythema and swelling in an area of skin. Diagnostic clues include: Pain out of proportion to that expected in a superficial soft-tissue infection. In those patients with neuropathy, however, pain may be absent10. Tenderness extending beyond the apparent area of cutaneous involvement. Spread of infection along deep fascial planes is usually well ahead of any cutaneous changes. Tenderness of seemingly normal adjacent tissue is an indication of the underlying pathological process11. Absence of lymphangitis, which may help differentiate NF from cellulitis. Lymphangitis is rarely seen in NF, as the infection is in a deeper plane than the cutaneous lymphatic channels. Cellulitis, in which the infection lies in the deep dermis and subcutaneous tissue, is more likely to produce lymphangitis11. Signs of rapidly progressive systemic sepsis. Initial skin erythema and swelling is followed by progressing red/purple discolouration, giving a bruised appearance. Epidermolysis follows, with blister formation. Spread of infection along fascial planes causes local thrombosis and ischaemia of the subcutaneous fat and skin. Crepitus may be felt, as bacteria (especially clostridial species) produce gas in the deep fascial planes10. Spontaneous splitting of the skin releasing grey, foul-smelling fluid is a late sign10. The benefits of imaging should be considered against the risks of a delay in treatment. In Brown et al.5, around one-third of patients with NF who had plain X-rays at presentation had the appearance of gas in the subcutaneous tissue. CT and MRI can aid diagnosis in equivocal cases4, but may be time-consuming. The laboratory risk indicator for NF (LRINEC) score was developed to distinguish patients with NF from those with cellulitis or an abscess12. It uses six biochemical markers to stratify patients into low-, moderate-, and high-risk groups. A systematic review by Bechar et al.13 found the LRINEC score to be a useful adjunct in the clinical diagnosis of NF, with a statistically positive correlation between the LRINEC score and a true diagnosis of NF. However, it performed poorly on external validation14 and should thus be used with caution. A finger sweep test (Fig. 1) may aid diagnosis and can be performed at the bedside10. Under local anaesthetic, a small incision is made down to the deep fascia. Absence of bleeding, discolouration of fat, and dirty ‘dishwater’ fluid are positive signs of NF. Minimal resistance to blunt digital dissection at the deep fascial level is also suggestive. Fluid samples can be sent for examination, although the most reliable culture results are gleaned from specimens from the spreading periphery of infection, obtained during surgical exploration. The combination of surgical exploration, microbiological and histopathological analysis of soft tissue is considered the ‘gold standard’ for confirming a diagnosis of NF, when it is in doubt3. Clinicians should maintain a high index of suspicion and a low threshold for proceeding to surgical exploration and debridement, as this is the only way to accurately confirm or exclude a diagnosis of NF10. Necrotizing fasciitis of the neck and upper trunk. Note finger sweep incision on the anterior chest The mainstays of initial management are resuscitation, intravenous broad-spectrum antibiotics, and aggressive surgical debridement (Fig. 2). Key steps in the management of necrotizing fasciitis The requirement for resuscitation will depend on the patient’s clinical condition on presentation, but, in patients presenting in septic shock, invasive monitoring, fluids, and ionotropic support are normally required to achieve haemodynamic stability. Antibiotics are given empirically as soon as the diagnosis of NF is suspected. Many areas have local guidelines indicating preferred antibiotic agents, but, in general, both Gram-positive and Gram-negative bacteria must be covered. Once the results of cultures are available, the antibiotic regimen can be modified to provide more targeted treatment. Intravenous immunoglobulin has been described as an effective method of neutralizing streptococcal toxins and may therefore prove beneficial in NF caused by group A streptococci. However, a survival benefit is yet to be demonstrated in randomized studies3,15–17. Surgical debridement is life-saving and is the mainstay of treatment. Local tissue ischaemia prevents antibiotics from penetrating to the source of infection and thus excision of necrotic or ischaemic tissue is vital to provide source control. Initial debridement should be early and aggressive (Fig. 3), as delayed and inadequate debridement have both been shown to increase mortality18. The procedure usually starts with an incision through necrotic skin to allow assessment of the underlying deep fascia and muscle, and confirmation of the diagnosis of NF. Excision of all necrotic skin, subcutaneous fat, fascia, and muscle then follows in a systematic circumferential manner. When blunt dissection with a finger no longer easily separates the fascia from the subcutaneous tissue, and the remaining tissue looks healthy, debridement can be considered complete7. a and b Debridement of necrotizing fasciitis to the right arm, chest and flank Post-debridement wounds may be extensive and exude heavily, requiring frequent dressing changes. Vacuum-assisted closure (VAC) devices are often beneficial, but can prove difficult to use in moist, contoured areas like the perineum. In cases of severe sepsis, wounds may bleed due to disseminated intravascular coagulopathy (DIC). A re-look procedure at 24–48 h to further clean and debride wounds is mandatory and should be repeated until the wound is deemed clean and stable. Throughout this period, patients often require treatment in an ITU setting, with careful attention to nutritional support, as metabolic demands are increased3. NF affecting some anatomical sites requires special consideration. Fournier’s gangrene may affect the perineum, genitalia, groins, lower abdomen, buttocks, or inner thighs. In male patients, the scrotal sac and penile skin are commonly lost, exposing the testes. Orchidectomy is not usually necessary, as the vascular supply to the testes is different from that of the scrotum. When necessary, the testes may be temporarily placed in subcutaneous pockets in the medial thigh before being returned to a reconstructed scrotal sac6. Anal sphincter damage is uncommon, but faecal diversion via a stoma is occasionally used to reduce faecal wound contamination. A recent meta-analysis showed that diversional stoma formation was a predictor of poor outcome and did not reduce overall mortality19. Abdominal-wall NF may be a consequence of intestinal pathologies, such as a strangulated hernia with bowel perforation, but may also occur in surgical wounds after open or laparoscopic abdominal procedures. In these cases, debridement may leave a full-thickness abdominal-wall defect, presenting challenges in wound management and reconstruction. The principles of treatment of NF affecting the limbs are the same as elsewhere, but, in extreme cases, amputation may be considered as a life-saving procedure. In patients who are unstable, amputation may be quicker and reduce blood loss compared with radical debridement. The following have been suggested as indications for considering amputation20: co-morbidities with a high anaesthetic risk (e.g. poorly controlled diabetes mellitus); extensive tissue necrosis with involvement of underlying muscles; shock requiring more than one inotrope; concurrent vascular insufficiency; and rapidly progressing infection with a large area of tissue necrosis. In the post-acute phase, rehabilitation and reconstruction are considered once patients are clinically stable and nutritionally optimized. Scrupulous wound management and active physical therapy are vital and patients should be mobilized as soon as possible. Early surgical reconstruction aims to heal wounds as rapidly as possible, reducing the metabolic burden on the patient. This often requires input from a plastic surgeon and will usually involve using split-thickness skin grafts (Fig. 4). Recent advances include the use of a synthetic dermal substitute to increase the eventual pliability of the grafted areas21. More complex reconstruction using tissue expansion or tissue flaps can be considered once patients are fully recovered. a and b Reconstruction using a skin substitute and split-thickness skin grafts The authors have no funding to declare. The authors declare no conflict of interest.