Soft Tissue Abscess

Abscess: Walled-off liquefied collection of necrotic tissue, inflammatory cells, & bacteria

Most commonly affects single site: Typical lymph node location vs. other subcutaneous or intramuscular focus

• Septic emboli can cause multifocal collections

Ultrasound: Excellent for detecting superficial collections & defining drainability

• Thick-walled centrally avascular collection with surrounding edema ± hyperemia

• Swirling internal debris upon compression

MR: Clearly defines deep extent, evaluates adjacent bone/cartilage/joint, & helps exclude other diagnoses

• Centrally nonenhancing fluid collection with thick, enhancing wall & peripheral poorly defined edema

• Whole-body MR may be useful to screen large territories for drainable collections in setting of systemic infection

Soft tissue sarcoma, lymphatic malformation, hematoma

Staphylococcus aureus > > streptococcal species

• ↑ incidence of methicillin-resistant S. aureus (MRSA)

Bartonella henselae : Regional lymphadenitis ± suppuration in cat scratch disease

Presentation: Swelling, fluctuance, erythema, tenderness, limited motion, fever, sepsis

Treatment: Drainage procedure ± antibiotics (IV or oral)

• With adequate drainage of abscess & no cellulitis, antibiotics may not be required

• Small abscess without drainable fluid collection may be treated with antibiotics & topical care only

• Trial of oral antibiotics in systemically well person

Pyomyositis, suppurative lymphadenitis