The purpose of this study is to determine if soft tissue infections in pediatric patients can be more accurately diagnosed (i.e. the presence of a drainable abscess) with the addition of bedside ultrasound to the clinical examination compared to the clinical examination alone.

Skin and soft tissue infections, particularly abscesses caused by community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are a growing public health problem. The treatment of a skin abscess usually requires incision and drainage or needle aspiration. In addition to providing definitive therapy, appropriate drainage can allow for organism identification and antibiotic susceptibility testing should antibiotics be utilized. A skin cellulitis, which is treated with systemic antibiotics and supportive care alone, may be hard to distinguish from an abscess, as both have similar clinical features. Therefore, as the presence or absence of purulent material may be difficult to determine, children may undergo an unnecessary drainage procedure. If drainage is avoided, the patient may require a subsequent ED visit if the diagnosis is missed on initial examination. This can lead to worsened clinical outcome, an extra financial burden for the family, and added emotional distress for the patient.

Bedside emergency ultrasound (EUS), which has been used since the mid-1980s is being used in adults to detect fluid collections such as soft tissue abscesses. Studies in adult patients have shown that EUS adds useful information to the history and physical examination and may even alter physicians' clinical impressions and management of patients. Currently, it is not known whether children represent a different population for EUS than adults and how EUS would perform in the pediatric outpatient setting. With improved diagnosis of soft tissue infections, better epidemiologic data about organism prevalence, improved and more prompt treatment, and more appropriate use of antibiotic therapy can be done.

To date, no study exists evaluating its utility specifically for the evaluation of soft tissue infections in pediatric patients. The goal of this study is to evaluate the test characteristics of EUS in pediatric patients presenting with evidence of soft tissue infection.

Inclusion Criteria:

• Evidence of at least one of the following: skin elevation, induration, tenderness, fluctuance, or history of purulent drainage from the lesion

Exclusion Criteria:

• Suspected paronychia or felon
• Lesion involving the face, perirectal, or vaginal area
• Surgical wound infection
• Underlying immunodeficiency
• Non-soft tissue infectious mass (e.g. lymphadenitis)
• Suspected non-infectious mass (e.g. hernia, lymph node)

Patients will be recruited from the emergency department at a tertiary care children's hospital with annual census of 78,000 patients per year.

Potential misclassification of lesions based on reference standard. Biased lesion outcome, as ultrasound results were not incorporated into patient care.

Single institution