Necrotizing Soft Tissue Infections

Last updated: March 10, 2026

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
All factors that reduce immunity and blood flow
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
Pain out of proportion to examination, Altered mental status (a sign of systemic toxicity), and a strong bad smell are useful signs too
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

Reference Intervals ›

Biochemistry

ACTH	P: <80 ng/L
ALT	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alk. phosphatase	P: 30–130 U/L
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
ADH	P: 0.9–4.6 pmol/L
AST	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
CRP	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol AM	P: 450–700 nmol/L
Cortisol Midnight	P: 80–280 nmol/L
CK ♂	P: 25–195 U/L
CK ♀	P: 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P: 2–8 U/L ♂; >25 menopause
GGT ♂	P: 11–51 U/L
GGT ♀	P: 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron ♂	S: 14–31 μmol/L
Iron ♀	S: 11–30 μmol/L
Lactate (venous)	P: 0.6–2.4 mmol/L
Lactate (arterial)	P: 0.6–1.8 mmol/L
LDH	P: 70–250 U/L
LH	P: 3–16 U/L
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
PTH	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin ♂	P: <450 U/L
Prolactin ♀	P: <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin (erect)	P: 2.8–4.5 pmol/mL/h
Renin (recumbent)	P: 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
T4	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
TIBC	S: 54–75 μmol/L
Triglycerides	P: 0.50–2.3 mmol/L
T3	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate ♂	P: 210–480 μmol/L
Urate ♀	P: 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol cr.
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids ♂	28–30 μmol/24h
17-Oxogenic steroids ♀	21–66 μmol/24h
17-Oxosteroids ♂	17–76 μmol/24h
17-Oxosteroids ♀	14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
RBC ♂	4.5–6.5 ×10¹²/L
RBC ♀	3.9–5.6 ×10¹²/L
Hb ♂	130–180 g/L
Hb ♀	115–160 g/L
PCV ♂	0.4–0.54 L/L
PCV ♀	0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelets	150–400 ×10⁹/L
Reticulocytes	0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (bpm)
Neonate	140–160
Infant <1yr	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Respiratory Rate (tachypnoea)
0–2 months	≥60/min
2–12 months	≥50/min
1–5 years	≥40/min
>5 years	≥30/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn	13–20
1 month	11–18
2 months	10–15
1–2 years	10–13
>2 years	11–14
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

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