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Imaging features of soft-tissue infections

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Abstract

Skin and soft tissues are among the most common sites of infections. Infections can involve the superficial epidermis to deep muscles and bones. Most infections spread through contiguous structures, although hematogenous spread can occur in the setting of an immunocompromised state and with atypical infections. While clinical diagnosis of infections is possible, it often lacks specificity, necessitating the use of imaging for confirmation. Cross-sectional imaging with US, CT, and MRI is frequently performed not just for diagnosis, but to delineate the extent of infection and to aid in management. Nonetheless, the imaging features have considerable overlap, and as such, it is essential to integrate imaging features with clinical features for managing soft tissue infections. Radiologists must be aware of the imaging features of different infections and their mimics, as well as the pros and cons of each imaging technique to properly use them for appropriate clinical situations. In this review, we summarize the most recent evidence-based features of key soft tissue infections.

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Acknowledgments

The authors would like to extend their appreciation to Dr. Sergiy Kushchayev, Dr. Mohamed Jaryaya, Dr. Venkatesh M, Dr. Ameya Kawthalkar, Dr. Brian P. Kennedy, and Dr. Sandeep Singh Awal, whose generous provision of select images greatly enhanced the quality and comprehensiveness of this article. Their invaluable contributions are deeply appreciated.

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Authors and Affiliations

  1. North Bengal Medical College, Siliguri, West Bengal, India

    Devpriyo Pal

  2. Massachusetts General Hospital, Boston, MA, USA

    Shambo Guha Roy

  3. Mercy Catholic Medical Center, Darby, PA, USA

    Rajshree Singh

  4. University Radiology, East Brunswick, NJ, USA

    Mohammad Reza Hayeri

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Teaching points

1. Cellulitis and bland edema can appear very similar on imaging, but only cellulitis will show enhancement after IV contrast. Delayed-phase imaging is helpful in cases of vascular insufficiency.

2. Abscesses, typically characterized by peripheral rim enhancement, can still be effectively diagnosed in situations where intravenous contrast cannot be used. In such cases, Diffusion Weighted Images offer a valuable alternative, providing sensitivity and specificity on par with conventional methods.

3. Necrotizing Fasciitis is strongly indicated by specific MRI findings such as thickening of deep fascial layers (>3mm), fluid signal intensity within deep fascia, and heterogeneous enhancement. Presence of gas may confirm the diagnosis in some cases, but it is rare. CT is the primary choice for detecting gas, but its absence does not rule out Necrotizing Fasciitis. Timely surgical intervention is crucial in managing this surgical emergency, and imaging should not delay treatment.

4. Pyomyositis, as it advances through its clinical stages of muscle edema with fascial thickening, and the hallmark intramuscular abscess, can be clearly depicted with MRI.

5. Septic tenosynovitis and septic bursitis can exhibit signal characteristics that resemble those of non-infectious inflammatory conditions. In rare cases, gas bubbles may be observed within the bursa or tendon sheath. Tenosynovitis can be a surgical emergency, especially in the hand, and complications like osteomyelitis, tendon necrosis, or stenosing tenosynovitis are associated with a poor outcome.

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Pal, D., Roy, S.G., Singh, R. et al. Imaging features of soft-tissue infections. Skeletal Radiol (2024). https://doi.org/10.1007/s00256-024-04694-4

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