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Soft Tissue Infections

Wi lliam Thomas Smith, MD

N icole M. Deiorio, MD

Key Points

• Most cases of cel lul itis can be safely managed as

outpatients with oral antibiotics, elevation, and recheck

in 24-48 hours.

• All abscesses require drainage. Most patients can be

safely discharged without antibiotics, but do need a

recheck in 48 hours.

• Patients who are systemically ill or immune

compromised require intravenous (IV) antibiotics,

laboratory and imaging studies, and admission.

INTRODUCTION

Soft tissue infections represent a common complaint in the

emergency department (ED). The term "soft tissue infection''

refers to an infection of the skin and underlying tissue. It is the

emergency physician's objective to distinguish superficial

infections (cellulitis, erysipelas, or abscess) from deep infec ­

tions. If deep infections, such as necrotizing fasciitis, are not

emergently diagnosed, they can cause significant morbidity

and mortality.

Cellulitis is a progressive bacterial infection of the der ­

mis and subcutaneous fat that is associated with leukocytic

infiltration and capillary dilation (seen as erythema). It is

caused by bacterial invasion of the skin, most often by

Staphylococcus aureus, �-hemolytic streptococcus, and

gram-negative bacilli such as Haemophilus influenzae.

Methicillin-resistant Staphylococcus aureus (MRSA) is

quickly becoming a common infecting agent in many

community-acquired cases of cellulitis and abscesses.

Erysipelas is a skin infection that involves the lymphatic

drainage system. Primarily, it is caused by invasion of the

skin by Staphylococcus pyogenes in areas with impaired

1 51

• Patients with pain out of proportion to physical exam findings, crepitus, or rapidly spreading erythema may have a

life-threatening necrotizing infection requiring aggressive

work-up, broad-spectrum IV antibiotics, and immediate

surgical consultation for operative debridement.

lymphatic drainage. It is common in infants, children, and

older adults. It is usually found on the lower extremities

(70%) or face (20%). The characteristic presentation is

painful erythematous raised lesions, which may look like

an orange peel. Red streaking representing inflammation

of the underlying lymphatics may also be present.

Abscesses are localized pyogenic infections that can

occur in any part of the body. Approximately 2% of all

adult visits to the ED are for the treatment of cutaneous

abscesses. Bacteria that normally colonize the skin are

often the cause, with S. aureus being the most common

organism involved. Mixed infections (aerobes and anaerobes) usually occur in the perineal areas.

Necrotizing infections are life and limb-threatening

infections that involve the skin, subcutaneous tissue, fascia,

and muscle. They usually occur in the setting of skin t rauma,

surgical procedures, decubitus ulcers, and immune compromise. These deadly infections are caused by a mixture of

aerobic and anaerobic bacteria in most cases. Commonly

isolated bacteria include S. aureus, S. pyogenes (ie, "flesheating bacteria"), enterococci, and anaerobes such as

Bacteroides and Clostridium perfringens (ie, "gas gangrene").

CLINICAL PRESENTATION

� History

CHAPTER 36

Ask about the time course and presence of systemic symptoms.

Rapidly progressive infections with systemic symptoms

require aggressive care in the ED. Patients should be asked

about trauma (including bites, scratches, and possible foreign

bodies), as it is the most common risk factor for developing a

soft tissue infection. Other risk factors include obesity, malnutrition, immune compromise, intravenous (N) drug use,