Diagnosing necrotizing fasciitis: is there a difference between type I and type II with respect to computer tomography scan features?

PURPOSE: Necrotising fasciitis (NF) requires rapid diagnosis to prevent morbidity and mortality. Yet clinicians rely heavily on imaging to help guide diagnosis, but type II NF is caused by non-gas producing organisms. Thus, the aim of this study was to assess computer topography (CT) imaging findings of type I compared to type II NF.

METHODS

This was a retrospective study conducted by reviewing medical records with NF from 1/1/2020 to 12/31/2024 at a single medical centre. The presence of air on CT images was evaluated by reviewing radiology reports and manual review of imaging. Comparisons were made on imaging findings for type I compared to type II NF as well as based on location.

RESULTS

A total of 367 patients had type I NF and 90 patients had type II NF. When comparing the proportion of NF with gas seen on imaging (total 75.5%), the type I cohort had a statistically significant higher rate of gas present in the soft tissues (91.8% compared to 7.8% p˂0.0001). When this was separated by location there was a statistically significant difference in the rates of imaging with gas in all locations except the foot.

DISCUSSION: This study demonstrates that reliance on CT imaging to evaluate gas in soft tissues is not advantageous for diagnosing type II NF. Thus, this study reinforces that NF is a clinical diagnosis and CT findings without gas in the soft tissues do not exclude NF.