Comparison of Point of Care Ultrasound and Magnetic Resonance Imaging for the Diagnosis of Necrotising Soft Tissue Infections: A Cross-sectional Study

Abstract

Introduction: Necrotising fasciitis requires a high index of clinical suspicion in the early stages since it is difficult to distinguish it from common skin diseases like cellulitis or harmless wound infections. Despite improvements in antibiotic therapy and intensive care, Necrotising Soft Tissue Infections (NSTIs) still have a high mortality rate. Point-of-Care Ultrasound (POCUS) can increase the efficiency and precision of diagnostics. Magnetic Resonance Imaging (MRI) has a higher sensitivity and specificity in diagnosing the infection. However, Computed Tomography (CT) and MRI are not always readily available in clinical practice settings and can have other drawbacks, such as being a time-consuming and expensive method. Aim: To define how POCUS can be used as an initial and primary modality for diagnosis of NSTI. Materials and Methods: The present cross-sectional study was conducted in the Department of Radiodiagnosis, Stanley Medical College, Chennai, Tamil Nadu, India, from April 2021 to March 2022. A total number of 40 patients of any age group and sex, who were suspected to have soft tissue infections were included. After doing a bedside ultrasound in all 40 patients, in 36 MRI was performed. MRI was considered the gold standard technique in the diagnosis of NSTI. The Ultrasonography (USG) and MRI findings were compared. The imaging findings taken into consideration for predicting NSTI include subcutaneous thickening, subcutaneous fluid collection, muscular oedema, and subcutaneous air pockets. Sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV) were calculated. Results: The mean age of study population was 52 years. The incidence in males was 62.5% (25 patients) and in females was 37.5% (15 patients). The lower limb was the most frequently affected site involving the 25 (62.5%) patients. Out of 40 patients, 38 patients had subcutaneous thickening, 28 patients had subcutaneous fluid collection, 20 patients had muscular oedema and 13 patients had subcutaneous air pockets. Out of 13 patients who had subcutaneous air pockets four people had extensive air pockets and the USG findings were obscured in that four cases due to reverberation artifacts caused by air pockets. In the current study, POCUS has a sensitivity of 93.5%, specificity of 80%, PPV of 96%, NPV of 66.67%, and accuracy of 91.67%. Conclusion: According to the observations, the present study concluded that POCUS has a higher sensitivity in diagnosing NSTI.

Keywords

• cellulitis
• diabetes complication
• subcutaneous fat