CT in necrotizing soft tissue infection: diagnostic criteria and comparison with LRINEC score.

OBJECTIVE: To investigate which computed tomography (CT) criteria are most useful in diagnosing necrotizing soft tissue infection (NSTI) and how CT performs with respect to the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score.

METHODS: Patients who underwent CT for suspected NSTI were eligible for inclusion. LRINEC score was assessed. CT scans were evaluated for subcutaneous edema, fluid along superficial fascia, fluid along deep fascia, blurring of intermuscular fat planes, fluid collection, and air in the soft tissues. Surgical findings or clinical follow-up served as reference standard.

RESULTS: Fourteen patients with NSTI and 34 patients with non-NSTI were included. LRINEC score was significantly higher in patients with NSTI (median of 7.5 vs. 6, p = 0.039). Fluid along the deep fascia was significantly more frequently present in patients with NSTI (46.2% vs. 5.9%, p = 0.001). In multiple logistic regression analysis, presence of fluid along the deep fascia was significantly associated with NSTI (odds ratio [OR] = 10.28, 95% CI: 1.57 to 67.18, p = 0.015), whereas the LRINEC score was not significantly associated with NSTI (OR = 1.27, 95% CI: 0.92 to 1.74, p = 0.146). Using presence of fluid along the deep fascia as diagnostic criterion for NSTI, sensitivity was 46.2% (95% CI, 23.2 to 70.9%) and specificity was 94.1% (95% CI, 80.9 to 98.4%).

CONCLUSION: Fluid along the deep fascia was the only CT criterion which was significantly associated with NSTI and appeared more useful than the LRINEC score. In the right clinical setting, presence of this CT finding is highly suggestive for NSTI. Its absence, however, does not rule out NSTI.

KEY POINTS: • The presence of fluid along the deep fascia at CT is highly suggestive for NSTI in suspected patients. Its absence, however, does not rule out NSTI. `• The use of fluid along the deep fascia as a criterion appears to be more useful than the LRINEC score in diagnosing NSTI.