vascular or lymphatic insufficiency, surgical procedures, and

anything

decubitus ulcers. The past medical history can be r elevant, as

that depresses the immune system ( eg, steroids,

diabetes, immunosuppressive drugs, elderly) predisposes the

patient to soft tissue infections and may mask the severity of

illness. Also, the status of tetanus immunization and previous

antibiotic allergies should be ascertained.

� Physical Examination

Vitals signs provide rapid clues to the severity of infection.

Tachycardia and hypotension may indicate sepsis. Fever is

not reliable, as it occurs in <10% of patients with simple

cellulitis or abscess.

(

D

..&. Figure 36-1 . A. Cellu litis of the left leg.

B. Lymphangitis of the arm in a patient with a hand

infection. C. Necrotizing fasciitis of the lower extremity.

This patient req uired amputation of the leg to treat his

infection. Cou rtesy of Kevin jones, MD. D. Fournier's

gangrene extending up the back of a patient.

The skin examination is crucial, and it is important to

completely undress the patient to examine the involved

body part. Assess the involved area for erythema, warmth,

edema, and tenderness (Figure 36- lA). Lack of tenderness

helps differentiate infections from other causes of skin

SOFT TISSUE I NFECTIONS

erythema and warmth, such as venous stasis. Evidence of

lymphatic spread in the form of red lines tracking proximally

from the wound, called lymphangitis, further suggests an

infectious etiology (Figure 36-lB). Focal areas of fluctuance

and induration may indicate abscess formation.

Marking the extent of erythema on the patient with a

pen will allow for comparison on repeat examinations.

Rapid extension is concerning for a necrotizing infection

(Figures 36-lC and D). Crepitus suggests gas formation in

the tissues and is a sign of a more serious necrotizing infection. It is important to remember that necrotizing soft tissue infections often present with severe pain but may have

few findings on physical exam. The absence of crepitus

does not rule out a deep space infection.

Distal pulses should be examined to assess for arterial

insufficiency.

DIAGNOSTIC STUDIES

...... Laboratory

The diagnosis of simple cellulitis, erysipelas, or an abscess

is clinical. Basic laboratory studies, such as a complete

blood count or basic metabolic panel, are of little benefit.

However, they should be considered if there is a s uspicion

of necrotizing infection, immune compromise, a history

suggestive of hyperglycemia/metabolic abnormalities, or

systemic symptoms. A C-reactive protein may also be useful when considering a necrotizing infection, as it will be

significantly elevated. Gram stain and wound culture

should be obtained in patients with suspected MRSA

abscess and necrotizing infections, as it will guide future

antibiotic therapy. Routine blood cultures add little to the

diagnosis and treatment of soft tissue infections .

..... Imaging

Ultrasound is becoming more frequently utilized in the ED

for the diagnosis of cutaneous abscesses. It is fast, readily

available at the bedside, and can easily localize an abscess

for incision and drainage (Figure 36-2A). Ultrasound is

also more sensitive than plain radiographs for soft tissue

A

B

(

Figure 36-2. A. U ltrasound of a cutaneous abscess.

The abscess cavity is hypoechoic with mixed interna l

echogenicity. The surrounding skin is hyperechoic

because of adjacent tissue edema and possibly cel lulitis. B. Plain radiograph of the leg demonstrating subcutaneous air. C. CT scan in a patient with necrotizing

fasciitis of the abdominal wall (a rrow).

air. Plain radiographs are helpful to evaluate for traumatic

injury, osteomyelitis, and the presence of gas formation

(Figure 36-2B). However, radiographs are insensitive for

small amounts of air. Computed tomography scan remains

the most sensitive for soft tissue air, deep space abscesses,

and foreign bodies (Figure 36-2C).

CHAPTER 36

PROCEDURES

For a description of abscess incision and drainage, see

Chapter 1.