Investigations

• • Necrotising fasciitis is a clinical diagnosis and as such, the gold standard investigation is surgical exploration and tissue biopsy⁹.
• During surgery, a lack of resistance to blunt dissection of the normally adherent superficial fascia, accompanied by a lack of bleeding and the presence of foul-smelling ‘dishwater’ pus, confirm the diagnosis⁹.

(i) Laboratory Investigations

• • Appropriate initial ED investigations are as for all patients presenting with sepsis – FBC, U+Es, LFTs, coagulation screen, CRP, lactate, ABG/VBG and blood cultures.
  • Bloods may show leucocytosis, acidosis, altered coagulation profile, hypoalbuminaemia and abnormal renal function.¹⁰

(ii) Imaging

• • CT, US and MRI have all been used to image necrotising soft tissue infection, however no imaging modality is considered definitive and it is vital to ensure that if imaging is performed, it must not unduly delay surgical intervention.

(iii) Adjuncts – Laboratory Risk Indicator for Necrotising Fasciitis⁹

• • As an adjunct to clinical judgement, scoring systems such as the Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC) have been developed to help differentiate necrotising fasciitis from other soft tissue infections.
  • The LRINEC was developed following retrospective review of 89 cases of NF compared with 225 cases of other soft tissue infection and those variables which were most statistically significant discriminators combined to give a score.
  • Scores of six or more should raise the suspicion of NF and a score of eight or more is strongly predictive of the disease.

Learning Bite

Necrotising fasciitis is ultimately a clinical diagnosis – results of other investigations are supportive only. If you suspect necrotising fasciitis prompt treatment should be instituted without delay!