Necrotizing soft tissue infections (NSTI) are a rapidly progressive infection resulting in extensive necrosis of soft-tissue structures. It can develop into a life-threatening condition WITHIN HOURS (rapid onset and fulminant course)
NSTI leads to severe systemic morbidity and mortality if not diagnosed and treated promptly. Mortality is between 25-40%.
Spectrum of NSTI
| Depth | Term used |
|---|---|
| Skin and subcutaneous tissue | Necrotizing cellulitis |
| Fat | Necrotizing adipositis (most common) |
| Fascia | Necrotizing fasciitis |
| Muscle | Necrotizing myositis i.e. Gas gangrene |
Classification of NSTI based on Anatomic Location
| Location | Term Used |
|---|---|
| Scrotum and/or Perinuem | Fournier’s gangrene |
| Abdomen (contamination by colostomy) | Meleney’s gangrene |
| Neck and floor of the mouth | Cervicofascial necrotizing fasciitis |
| Face | Cancum oris (Noma) |
Classification of NSTIs
| Type | Description | Organisms |
|---|---|---|
| Type I | Polymicrobial (most common) | Gram-positive, gram-negative, anaerobes e..g Clostridium perfringens and Clostridium septicum |
| Type II | Monomicrobial | Beta-hemolytic streptococcus (Group A Streptococcus), Staphylococcus aureus, MRSA |
| Type III | Rare infection after salt-water exposure or Clostridial myonecrosis | Vibrio vulnificus, Clostridium spp. |
- Patient history
- Trauma
- Immuosuppression
- Diabetes Mellitus
- Obesity
- Alcohol abuse
- Intravenous drug use
- Malnutrition
- Renal failure
- Cirrhosis
- Malignancy
- Signs and symptoms
- Diffuse erythema (manifests initially as suspected cellulitis that does not respond to antibiotics)
- Bullae and vesicles
- Extreme tenderness (out of proportion to the area of erythema)
- A woody hard texture of the subcutaneous tissue (the area of subcutaneous involvement is larger than the area of skin involvement)
- Crepitus (due to gas produced by the bacteria or air leaking into the tissues)
- Purple skin discoloration (skin necrosis AND ecchymosis)
- Paraesthesias
- Inability to distinguish fascial planes and muscle groups on palpation
- Fever, chills, tachycardia, hypotension, and altered mental status (signs of systemic toxicity)
- “Hard signs” are used to diagnose necrotizing fasciitis
- HypotensionCrepitusSkin necrosisBullaeGas on X-ray
- Differentials
- Ecthyma gangrenosum: Ulcerative lesion extending into the dermis that develops in the setting of bacteremia. The most common causative organism is Pseudomonas aeruginosa
- Cellulitis
- Deep Venous Thrombosis
- Erysipeloid: Cellulitis caused by Erysipelothrix rhusiopathiae
- Lymphogranuloma venerium
- Herpetic whitlow
- Eczema herpeticum
- Shingles
- Acne vulgaris
- Atopic dermatitis
- Hidradenitis suppurativa
- Vascular malformation
- Investigations
- CBC: Leukocytosis
- RBS: may show hyperglycemia
- UECs: Deranged
- CRP, ESR, or Procalcitonin: Elevated
- CK: Elevated
- HIV test
- Group and cross-match
- Blood culture: 2 sets
- Gram stain and culture from deep tissue: obtained during surgical exploration
- X-Ray: Gas in soft-tissue
- CT/MRI: shows gas in soft tissue, fascial thickening, and oedema
- Treatment
- Broad-spectrum antibiotics
- Antitoxin antibiotics
- Wide surgical debridement
- Hyperbaric oxygen
- Reconstruction
