Necrotising fasciitis develops when organisms migrate from subcutaneous tissue along fascial planes. Although muscle is typically spared by the organisms themselves, necrosis of muscle tissue can still occur because of compartment syndrome.
A wide range of organisms can cause NF including:
Group A streptococcus
Gram-negative organisms such as Vibrio spp and Aeromonas hydrophilia which are typically acquired from seawater contamination of wounds
Fungal infection (e.g. candida)
In many cases of NF the cause is polymicrobial (i.e. a mixture of aerobic and anaerobic bacteria).
Pain which is out of proportion to the clinical findings
Typical findings on clinical examination include:
Local pain, swelling and erythema
Poorly defined margins with pain extending beyond the margins of erythema
Crepitus on palpation of the skin
Offensive discharge which may have a typical ‘dishwater’ appearance
Oedema (which may be tense)
Systemic features may include:
Hypotension and tachycardia
Relevant laboratory investigations include:
FBC: white cell count will typically be significantly elevated (unless immunocompromised)
U&Es: hyponatraemia may be associated with NF
CRP: typically elevated in the context of NF
Creatinine kinase: typically elevated in the context of NF secondary to myonecrosis
Lactate: typically elevated in the context of NF
Blood cultures: to identify causative organisms which may also be within the circulation.
Coagulation screen: as part of a pre-operative workup
Group and save: as part of a pre-operative workup
Relevant microbiologicalinvestigations include:
Blood cultures (mentioned above)
Debrided tissue gram-stain and culture
Although imaging can be valuable, it should not delay emergency surgical management.
A CT of the affected area may reveal gas produced by the organisms and help assess the extent of spread.
Bedside finger test
The bedside finger test is sometimes performed by plastic surgeons and involves the following steps:
A small incision is made down to the fascia under local anaesthetic.
The tissue is then probed with a sterile gloved finger.
Findings associated with NF include an absence of bleeding, purulent pus and a lack of normal tissue resistance to blunt dissection.
Necrotising fasciitis is a clinical diagnosis, but investigations can help inform further medical and surgical management.
A structured ABCDE assessment should be performed to identify and treat issues such as haemodynamic instability.
Broad-spectrum intravenous antibiotics should be administered as soon as possible according to local guidelines (covering streptococci, staphylococci, gram-negative rods and anaerobes).
Urgent surgical debridement is required to remove the infected tissue in the hope of halting further spread of the infection to surrounding tissue.
After initial debridement, the wound is monitored and may require further debridement until the infection is controlled.
Necrotising fasciitis (NF) is a rare but life-threatening infection involving any layer of the deep soft tissue compartments (i.e. dermis, subcutaneous tissue, fascia or muscle).
A wide range of organisms can cause NF and in most cases the infection is polymicrobial.
Risk factors for the development of NF include skin injury, impaired immunity and intravenous drug use.
Typical symptoms of NF include pain which is out of proportion to the clinical findings, skin discolouration, blisters, fever and malaise.
Typical findings on clinical examination include local pain, swelling and erythema with poorly defined margins. Other findings may include crepitus on palpation, offensive discharge, oedema and bullae.
Investigations for NF include basic blood tests, blood culture, wound swabs, debrided tissue culture, CT and the bedside finger test.
NF is a clinical diagnosis but investigations can help inform further medical and surgical management.
Medical management of NF includes an initial ABCDE assessment and the administration of broad-spectrum IV antibiotics.
Surgical management involves debridement of the affected tissue with close monitoring post-operatively.
Mr Zakir Shariff
Consultant Plastic Surgeon
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Piotr Smuszkiewicz, Iwona Trojanowska and Hanna Tomczak. Necrotising fasciitis. License: [CC-BY]