Ultrasound: Soft tissue

Background

  • Soft tissue ultrasound can help with differentiating abscess from cellulitis
  • Many types of foreign bodies can be visualized

Cellulitis

Images

Cellulitis and cobblestoning

Instructions

  1. Select linear probe (high frequency probe)
  2. Scan area of concern (orientation of probe not as important)
  3. Rotate 90° over area of concern

Findings

  • Positive
    • Cobblestoning - thin lines of fluid between fat globules
    • Loss of tissue plain definition

Pearls and Pitfalls

  • Cobblestone can also be present in:
    • Lymphedema
    • Pitting edema secondary to HF

Abscess

Novice sonographers can predict a positive I&D with SN 0.97 and SP 0.67 (vs clinical exam 0.76 and 0.83)[1]

Images

Instructions

  1. Select linear probe (high frequency probe)
  2. Scan area of concern (orientation of probe not as important)
  3. Rotate 90° over area of concern
  4. If hypoechoic area is identified, apply gentle pressure over area

Findings

  1. Positive scan (not all elements are required to make a diagnosis)
    • Fluid collect seen has heteroechoic or hypoechoic circular area
    • Hyperechoic ring
    • Posterior acoustic enhancement
    • Swirling or Squish Sign (movement of abscess debris) with compression
    • Irregular borders

Pearls and Pitfalls

  • Color flow may be used to differentiate vascular and lymphatic structures
  • In the inguinal crease strangulated bowel can mimic abscess
  • The collection seen under U/S may not correspond with actual collection size
  • Hematomas can look similar to abscess, so the right clinical context is needed

Foreign Body

Images

Instructions

  1. Select linear probe (high frequency probe)
  2. Scan area of concern (orientation of probe not as important)
  3. Rotate 90° over area of concern

Findings

  • FB can show 2 different signs
    • Acoustic shadow - Ring down appearance
      • Common with wood and splinters
    • Reverberation
      • Common with metal such are retained insulin needle

Pearls and Pitfalls

  • U/S is no sensitive for FB (U/S will miss a substantial amount of FBs)
    • Xray or other modality may be needed for look during negative exams
  • Real-time U/S can aid in FB removal
  • Water baths may be helpful for extremities
  • Scar tissue may mimic FB

See Also

External Links

References

  1. Berger, T, et al. Bedside ultrasound performed by novices for the detection of abscess in ED patients with soft tissue infections. Am J Emerg Med. 2012; 30(8):1569-73. doi: 10.1016/j.ajem.2011.08.002.