Why it matters
Necrotising soft-tissue infection is a rapidly progressive infection of fascia and subcutaneous tissues with systemic toxicity. Delay in operative source control markedly worsens outcome.
Clinical suspicion
Important features include:
- severe pain, sometimes out of proportion to early skin findings
- rapidly progressive swelling or erythema
- systemic toxicity
- skin anaesthesia, dusky discoloration or bullae in advanced disease
- crepitus in selected infections
- deterioration despite apparently appropriate treatment for cellulitis
At operation, concerning findings include grey or necrotic fascia, thin turbid fluid, loss of normal tissue resistance and poor bleeding from devitalised tissue.
Investigations
Blood tests and imaging can support assessment but must not delay surgery in a patient with convincing clinical features. A risk score may increase suspicion but cannot reliably rule the diagnosis in or out.
CT or MRI can demonstrate fascial oedema, fluid or gas, but a normal scan does not exclude early disease.
Management
Management is simultaneous rather than sequential:
- immediate resuscitation
- broad-spectrum intravenous antimicrobial therapy according to local microbiology guidance
- urgent senior surgical exploration and radical debridement
- microbiology and tissue samples from the operating theatre
- intensive-care support when required
- repeated planned inspection and further debridement until all remaining tissue is viable
The definitive operation may be extensive. Preserving clearly necrotic tissue to reduce the size of the wound is unsafe.
Reconstruction
Once infection is controlled and physiology has stabilised, reconstruction may require:
- delayed primary closure
- split-skin graft
- local or regional flap
- free flap
- amputation when infection or tissue loss precludes useful salvage
Negative-pressure therapy can assist wound management between procedures but is not a substitute for adequate debridement.
Definitive closure is delayed until infection is controlled and tissue viability is clear. Reconstruction may require grafts or flaps.
Clinical emergency
Necrotising soft-tissue infection is a rapidly progressive infection of fascia and soft tissue with systemic toxicity. Delay in surgery can be fatal.
Early findings can be deceptively modest. Features raising concern include:
- pain out of proportion
- rapid progression
- swelling and erythema
- systemic toxicity
- skin anaesthesia
- bullae
- crepitus
- dusky or necrotic skin
Late skin signs should not be awaited before escalation.
Risk factors
Risk is increased by:
- diabetes
- immunosuppression
- vascular disease
- renal disease
- recent surgery or trauma
- injection injuries
- obesity
However, healthy patients can also be affected.
Diagnosis
This is primarily a clinical diagnosis.
Blood tests and imaging may support suspicion but should not delay surgery in a toxic patient with convincing findings.
CT can show gas, fascial thickening or fluid; MRI is sensitive for fascial involvement but is often impractical in an unstable patient.
Surgery
Urgent radical debridement is the key treatment.
Principles:
- expose the involved compartments adequately
- excise all necrotic skin, fascia and muscle
- send multiple deep samples
- leave questionable tissue for planned re-inspection only if genuinely viable enough to justify it
- return for repeat debridement as needed
The endpoint is viable bleeding tissue and control of the advancing infection.
Antibiotics and critical care
Broad-spectrum intravenous antibiotics should cover:
- gram-positive organisms
- gram-negative organisms
- anaerobes
Therapy is narrowed when microbiology becomes available.
Patients often require:
- aggressive resuscitation
- vasopressor support
- organ support
- management in critical care
A toxin-suppressing agent may be included when streptococcal or clostridial infection is suspected according to protocol.
FRCS synthesis
The safest exam answer is unequivocal: suspected necrotising infection in a toxic patient is a surgical emergency; imaging must not create delay.