Necrotising fasciitis (I) Flashcards
Define necrotising fasciitis.
Life-threatening subcutaneous soft-tissue infection that progressively extends to the deep soft tissues including muscle fascia and overlying fat, but not into the underlying muscle
Requires a high index of suspicion for diagnosis
What are the different types of necrotising fasciitis?
- type I
- type II
- type III
- type IV
What is type I necrotising fasciitis?
- polymicrobial infection caused by mixed aerobe and anaerobes
- anaerobe (e.g. Bacteroides) + facultative anaerobe (E. coli, Enterobacter, Klebsiella) or non-group A Streptococcus +/- S. aureus
- more commonly post-surgery in diabetics
What is type II necrotising fasciitis?
- monomicrobial infection most commonly caused by Streptococcus pyogenes (group A Streptococcus)
- Panton-Valentine leukocidin (PVL)-positive S. aureus and MRSA are also potentially causative organisms
What is type III necrotising fasciitis?
Caused by freshwater exposure associated with Aeromonas hydrophilia, and saltwater exposure or consumption of raw oysters associated with Vibrio vulnificus
What is type IV necrotising fasciitis?
Fungal pathogens such as mucormycosis
What is the most commonly affected site of necrotising fasciitis?
Perineum (scrotum/vulva)- called Fournier’s gangrene
What is a major risk factor for Fournier’s gangrene (necrotising fasciitis)?
Use of an SGLT-2 inhibitor (-flozins) in T2DM - inhibits SGLT-2 cotransporter in PCT, increasing urinary excretion of glucose –> increases chance of UTI including necrotising fasciitis
What are the clinical features of necrotising fasciitis? (10)
- anaesthesia or severe pain over site of infection
- fever
- palpitations, tachycardia, tachypnoea, hypotension and lightheadedness
- nausea and vomiting
- delirium and crepitus (advanced cases)
- vesicles or bullae
- grey discolouration of skin
- oedema or induration
- location of lesion - extremities, perineum, trunk, head and neck
- haemorrhagic blisters may be present
What systemic signs of infection are seen in necrotising fasciitis? (7)
- fever
- palpitations
- tachycardia
- tachypnoea
- hypotension
- light-headedness
- nausea and vomiting
What does necrotising fasciitis often present as?
Rapidly worsening cellulitis with pain out of keeping with physical features
When should we always suspect necrotising fasciitis? (6)
- rapidly progressing soft tissue infection
- severe pain (disproportionate to clinical findings)
- anaesthesia over site of infection
- oedema and erythema (oedema extends beyond erythema)
- systemic signs of infection
- patient may present earlier in disease process with non-specific signs and symptoms
What are some risk factors for necrotising fasciitis? (8)
- DM - immunosuppression, SGLT2i use
- IVDU
- cutaneous trauma
- surgery
- varicella zoster infections/chickenpox
- PVD
- chronic renal/hepatic insufficiency
- medications - corticosteroids
What type of diagnosis is necrotising fasciitis?
Clinical diagnosis - if you suspect necrotising fasciitis, immediately refer the patient for urgent surgical debridement; do not wait for the results of Ix before referral
What are the main investigations we do for necrotising fasciitis?
Surgical exploration - finger test (minimal resistance to finger dissection), absence of bleeding, presence of necrotic tissue, murky or greyish ‘dishwater’ fluid
Then blood and tissue cultures and gram stain
