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# Necrotizing soft tissue infection (necrotizing fasciitis, gas gangrene)

A rare, fast-spreading infection that kills skin, fat, fascia and muscle. It is a surgical emergency: early surgery to remove dead tissue saves lives.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Muscle dividers](https://durgical.com/en/anatomy/lateral-femoral-intermuscular-septum/)
- [Gastrocnemius (inner head)](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/)
- [Skin](https://durgical.com/en/anatomy/skin/)
- [Fascia lata](https://durgical.com/en/anatomy/fascia-lata/)
- [Soleus](https://durgical.com/en/anatomy/soleus-muscle/)
- [Tibialis anterior](https://durgical.com/en/anatomy/tibialis-anterior-muscle/)
- [Great saphenous vein](https://durgical.com/en/anatomy/great-saphenous-vein/)
- [Scrotum](https://durgical.com/en/anatomy/scrotum/)
- [Perineal body](https://durgical.com/en/anatomy/perineal-body/)

## Microorganisms that cause it

- [Streptococcus pyogenes](https://durgical.com/en/microbiology/streptococcus-pyogenes/)

## Why it happens

- [How septic shock develops](https://durgical.com/en/general-pathology/how-septic-shock-develops/)
- [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/)
- [Skin: epidermis layers, dermis, hypodermis](https://durgical.com/en/histology/skin-epidermis-layers-dermis-hypodermis/)

## What it is

A rapidly progressive bacterial infection that destroys the subcutaneous tissue and the fascia and may reach muscle (myonecrosis, gas gangrene). It spreads along fascial planes faster than the skin shows, and it causes sepsis and death without urgent surgery.

## Who gets it

Uncommon but seen in emergency and surgical services everywhere, including Colombia. Most patients have diabetes, obesity, peripheral vascular disease or another immune problem. Fournier gangrene, the perineal and genital form, mostly affects men with diabetes.

## Causes

- Type I (polymicrobial): anaerobes, enteric gram-negative bacilli and streptococci; most common, usually in diabetes, perineum or trunk
- Type II (monomicrobial): group A streptococcus, sometimes with Staphylococcus aureus including MRSA; often in healthy people after minor trauma
- Clostridium perfringens and other clostridia: gas gangrene after deep, contaminated or crush wounds
- Vibrio vulnificus and Aeromonas after exposure to sea or fresh water

## Risk factors

- Diabetes mellitus
- Obesity, peripheral artery disease and chronic [kidney](https://durgical.com/en/anatomy/kidney/) or [liver](https://durgical.com/en/anatomy/liver/) disease
- Immunosuppression, cancer and alcohol use disorder
- Injection drug use
- Surgery, penetrating or crush trauma, burns and chronic wounds
- Varicella lesions in children (group A streptococcus)

## Pathophysiology

Bacteria enter through a break in the skin and spread along the fascia, where blood supply is poor. Toxins and enzymes, together with thrombosis of the perforating vessels, cause necrosis of fat, fascia and skin; damaged nerves explain later anaesthesia of the area. Gas-forming organisms produce crepitus, and toxins released into the blood lead to septic or toxic shock.

## Classification

- Type I: polymicrobial
- Type II: monomicrobial, mostly group A streptococcus
- Clostridial myonecrosis (gas gangrene)
- By site: limbs, trunk, perineum (Fournier gangrene), [head and neck](https://durgical.com/en/anatomy/region/head-and-neck/)

## Symptoms and signs

- Severe pain out of proportion to the visible skin changes
- Swelling and tense, woody induration beyond the area of redness
- Skin that turns dusky, violaceous or bluish, with blisters or bullae
- Crepitus from gas in the tissues
- Fever, tachycardia and malaise
- Later loss of sensation in the skin and visible necrosis

## Red flags

- Pain that is far worse than the skin appearance suggests
- Rapid spread of redness or swelling over hours
- Haemorrhagic bullae, skin necrosis or crepitus
- Hypotension, confusion or other signs of shock
- Painful swelling of the [scrotum](https://durgical.com/en/anatomy/scrotum/), perineum or vulva in a person with diabetes

## Diagnosis

**Clinical**
A clinical and surgical diagnosis. Rapid progression, disproportionate pain and systemic toxicity should lead to urgent surgical exploration, which shows grey, necrotic fascia that separates easily from tissue, with thin 'dishwater' fluid and no bleeding.

**Tests**
Blood count, sodium, glucose, creatinine, C-reactive protein, lactate and creatine kinase; the LRINEC score can raise suspicion but cannot rule the disease out. Blood cultures and Gram stain and cultures of operative tissue.

**Imaging**
Imaging must not delay surgery. Plain radiographs or CT may show gas in soft tissue; CT or MRI show fascial thickening and fluid along fascial planes. Point-of-care ultrasound may help at the bedside.

## Differential diagnosis

- Cellulitis and erysipelas
- Deep vein thrombosis
- Compartment syndrome
- Pyomyositis or abscess
- Calciphylaxis or vasculitic ulcers

## Goal of treatment

Remove all dead and infected tissue as early as possible, give broad antibiotics and support circulation, then reconstruct and rehabilitate.

## Treatment

**Surgical**
Urgent and repeated surgical debridement until healthy tissue remains; amputation when a limb cannot be saved; diverting colostomy may be needed in Fournier gangrene.

**Medical**
Empirical broad-spectrum intravenous antibiotics covering gram-positive (including MRSA), gram-negative and anaerobic organisms, plus clindamycin to suppress toxin production, adjusted to cultures.

**Acute**
Sepsis resuscitation with fluids and vasopressors, glucose control and intensive care support.

**Procedure**
Wound care with negative-pressure dressings, later [skin](https://durgical.com/en/anatomy/skin/) grafts or flaps; hyperbaric oxygen is used in some centres as an adjunct.

**Rehabilitation**
Physical therapy, nutritional support and rehabilitation after extensive debridement or amputation.

## Complications

- Septic or streptococcal toxic shock
- Multiorgan failure
- Limb amputation
- Large tissue loss with disfiguring scars and contractures
- Death

## Prognosis

Mortality remains high, roughly one in five or more, and rises with every hour of delay to surgery, older age, shock and comorbidity. Survivors often need several operations and long rehabilitation.

## Prevention

- Prompt cleaning and care of wounds, especially in people with diabetes
- Good glycaemic control and foot care in diabetes
- Early medical review of wounds with spreading redness, severe pain or fever

## Test yourself

Think of the answer, then tap the question to see it.

## What is the classic early clinical clue to necrotizing fasciitis?

Pain out of proportion to the visible skin findings, with rapid progression and systemic toxicity.

## What is the definitive treatment of necrotizing fasciitis?

Urgent, often repeated, surgical debridement of all necrotic tissue, together with broad-spectrum antibiotics.

## Which organism causes gas gangrene (clostridial myonecrosis)?

Clostridium perfringens, usually after deep, contaminated or crush wounds.

## What is Fournier gangrene?

Necrotizing fasciitis of the perineum and genitals, usually polymicrobial and most common in men with diabetes.

## Should imaging delay surgery when necrotizing fasciitis is suspected?

No; it is a clinical-surgical diagnosis and exploration should not wait for imaging.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/necrotizing-soft-tissue-infection/)

## Related conditions

- [Cellulitis of the leg](https://durgical.com/en/conditions/cellulitis-of-the-leg/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Diabetic foot](https://durgical.com/en/conditions/diabetic-foot/)
- [Acute compartment syndrome](https://durgical.com/en/conditions/acute-compartment-syndrome/)
- [Toxic shock syndrome](https://durgical.com/en/conditions/toxic-shock-syndrome/)
- [MRSA and other multidrug-resistant organism infections](https://durgical.com/en/conditions/mrsa-and-other-multidrug-resistant-organism-infections/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Necrotizing soft tissue infection: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001443.htm) (MedlinePlus (U.S. National Library of Medicine), 2024); [About Necrotizing Fasciitis | Group A Strep | CDC](https://www.cdc.gov/group-a-strep/about/necrotizing-fasciitis.html) (Centers for Disease Control and Prevention (CDC), 2024).

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Source: https://durgical.com/en/conditions/necrotizing-soft-tissue-infection/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/necrotizing-soft-tissue-infection/