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Necrotising fasciitis and necrotising soft tissue infection

nec fasc · NSTI · necrotising soft tissue infection · flesh-eating infection · Fournier gangrene

A surgical emergency masquerading as cellulitis - the diagnosis is clinical suspicion and the treatment is the operating theatre.

ADMITBand A

Red flags

Recognise

On light skin

Early on, tense erythema indistinguishable from cellulitis; later a dusky, grey or mottled purple discolouration, haemorrhagic bullae, and skin anaesthesia over the affected area.

On brown and black skin

The early erythema that prompts the cellulitis diagnosis may be invisible, and the later dusky change is far harder to see against brown or black skin - both of which delay a diagnosis where delay measures directly in mortality. Do not wait for a colour change. Palpate: oedema extending beyond any visible margin, woody induration, crepitus and exquisite tenderness are all tone-independent, as is the pain-out-of-proportion that is the single most useful early sign. Skin anaesthesia over the area is a late but tone-independent finding.

In any skin tone

Distribution

Most often a limb, the perineum (Fournier gangrene) or the abdominal wall. The visible skin change is characteristically smaller than the area of underlying necrosis. In children the commonest route in is varicella - skin and soft tissue accounted for 46.3% of all varicella complications in a 253,221-child primary-care cohort.

Photographs

Necrotising fasciitis in an infant. The colour change is dusky purple-grey, not red - on dark skin the cellulitic erythema a clinician waits
Necrotising fasciitis in an infant. The colour change is dusky purple-grey, not red - on dark skin the cellulitic erythema a clinician waits for may never be visible, and by the time the skin breaks down as it has here the fascial plane underneath is long gone. Pain out of proportion, a rapidly advancing margin and a systemically unwell child matter more than the colour of the skin.
Fitzpatrick IV-VI (Fitzpatrick type estimated from the photograph, not stated by the source) · Oladokun RE, Lehloenya RJ, Hlela C, Ubesie AC, Katibi SO, Malande OO, Eley BS · Atlas of Paediatric HIV Infection, UCT Libraries Press 2018 - Chapter 1: Bacterial Infections, p12 · CC BY 4.0
Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

What to do in the ED

  1. Escalate to the on-call surgical team immediately on clinical suspicion - do not wait for imaging or bloods
  2. Resuscitate in parallel and treat as sepsis: fluids, cultures, lactate, and broad-spectrum intravenous antibiotics with anti-anaerobic and anti-toxin cover per local policy
  3. Mark the margin with the time and re-examine, so progression is measured rather than remembered
  4. Do not use LRINEC to rule out - see the caveat, this is the most important single point on this page
  5. CT if it will not delay surgery, recognising that imaging cannot exclude the diagnosis either
  6. Alert critical care early; definitive treatment is surgical debridement, and delay increases mortality

Score

LRINEC (with a rule-out caveat) — the calculator is in the interactive tool.

Disposition

ADMIT

Immediate surgical referral for debridement, with critical care involvement. Admission is to theatre, not to a ward.

Local variation

Which team takes necrotising infection varies by site - general surgery, plastics, orthopaedics or urology for perineal disease. Know the local route in advance; an argument about ownership is time the patient does not have.

Sources

Open this entry in the interactive tool