Pediatric Subcutaneous Abscess

  • Etiology: Bacteria (typically streptococcus) spread into subcutaneous tissues through breaches in epidermis forming an abscess which lies within the dermis and subdermal cutaneous layers
  • Imaging: Evaluate extension of collection looking for natural borders like fat and muscle interface or nearby cortical bone surface
  • Imaging US:
    — Round collection of anechoic or hypoechoic fluid which may show internal motion or swirling with compression
    — Borders often poorly defined
  • Imaging MRI:
    — T1WI post contrast: Enhancing rim with shaggy border
  • DDX: Lymph node, hematoma, inflammatory collection
  • Complications:
  • Treatment: Surgical
  • Clinical:
    — Typically presents as focal swelling with cellulitis in surrounding skin
    — May present with systemic signs of sepsis if bacteremia is present
    — Gluteus muscle is common site

Radiology Cases of Subcutaneous Abscess

US of subcutaneous abscess of knee
Transverse color doppler US of the left calf just inferior to the patella shows a well circumscribed, hypoechoic lesion in the sucutaneous tissues that is hypervascular in nature.
US of subcutaneous abscess
Transverse US of the axilla centered on the palpable mass shows an oval hypoechoic lesion in the subcutaneous tissue.