Microbial infection of subcutaneous tissue (cellulitis), muscle (myositis), tendon (tenosynovitis), or fascia (fasciitis)

Abscess is focal fluid collection containing suppurative inflammatory material

Cellulitis

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  Edematous, hyperechoic, hyperemic subcutaneous fat with thickened interlobular septa

Infectious tenosynovitis

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  Synovial tendon sheath is thickened, hyperemic, and contains fluid surrounding tendon

Infectious myositis

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  Hyperechoic, hyperemic, and indistinct, ± abscess

Necrotizing fasciitis

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  Spreads rapidly between tissue planes

  
  
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  Thickened, irregular fascia with perifascial fluid

  
  
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  Gas is highly specific but not always present

Abscess

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  Variable echogenicity, peripheral hyperemia, ± septation/gas

Route of spread can be direct (skin), postsurgical, or hematogenous

Deep soft tissue infection may require hospitalization, IV antibiotics, &/or surgery

Necrotizing fascitis is life threatening and early diagnosis decreases morbidity

Use wide field of view and increase depth to ensure entire area of abnormal tissue is imaged

Diagnose abscess by demonstrating fluctuance and lack of color Doppler flow

Note and report visible skin changes, breeches, or crepitus

Assess nearby joints for effusion (septic arthritis) and adjacent bone for cortical irregularity (osteomyelitis)