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Musculoskeletal/Small parts » Superficial Tissues
Retained foreign body in the soft tissues of the forehead
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Presentation Young female involved in a car accident about a month ago. Her head had crashed through the windshield. She now presents with painful swelling along her left lateral forehead.
 
 
 
Caption: Sagittal view through the region of swelling.
Description: Sagittal section showing soft tissue swelling, containing 2 linear highly echogenic structures with no acoustic shadowing. A standoff pad was used to maximize the resolution
 
 
 
Caption: Transverse section through the swelling.
Description: One of the echogenic structures seen here with surrounding hypoechoic rim.
 
 
 
Caption: Color Doppler view in the region of swelling.
Description: A color Doppler study demonstrates that it was poorly vascularized.
 
Differential Diagnosis Retained foreign body.
 
Final Diagnosis Retained foreign body reaction [given the history of crashing through a car windshield, these likely represent pieces of glass].
 
Discussion This is one of the cases which exemplifies the value of knowing the history of the patient. Following an injury, pieces of foreign body are very commonly retained in the body. Most commonly implicated are metal, glass and plastic particles. These then evoke a foreign body reaction, causing non-specific granuloma formation. These may cause serious inflammatory and infective complications. In recent years, reports regarding the use of ultrasonography, magnetic resonance imaging, and computed tomographic scanning to facilitate the detection of foreign bodies have been published;  however ultrasound emerges to be the most cost effective modality.

On ultrasound, metal appears as a highly echogenic structure, which usually demonstrates posterior acoustic shadowing. Glass or plastic particles also appear highly echogenic, but usually do not shadow, although sometimes they may show shadowing. Reverberation artifacts can also aid in the visualization of the foreign bodies.

A surrounding hypoechoic rim is usually seen surrounding the retained foreign body  if it has been there for more than 24 hours. This halo is thought to represent fibrinous exudates, granulation tissue and collagenous capsule formation. Power Doppler can show hypervascularity immediately surrounding the foreign body, known to correlate pathologically with granulation tissue and neovascularity. The case shown here did not show significant vascularity, as the foreign body reaction was quite chronic.

Ultrasound allows accurate and efficient detection of soft-tissue foreign bodies not visible on radiographs and also helps in the assessment of their associated complications. A stand off pad may or may not be used while scanning for improved resolution. Ultrasound can also be used to provide guidance to aid in the removal of foreign body.

 
Case References 1. Boyse TD, Fessell DP, Jacobson JA, Lin J et al. US of soft-tissue foreign bodies and associated complications with surgical correlation. Radiographics. 2001 Sep-Oct; 21(5): 1251-6.
 2. Jacobson JA, Powell A, Craig JG, Bouffard JA, van Holsbeeck MT. Wooden foreign bodies in soft tissue: detection at US. Radiology 1998; 206:45-48. 
3.Gilbert FJ, Campbell RS, Bayliss AP. The role of ultrasound in the detection of non-radiopaque foreign bodies. Clin Radiology 1990. Feb; 41(2): 109-12. 
4. Shiels WE 2nd, Babcock DS, Wilson JL, Burch RA. Localization and guided removal of soft-tissue foreign bodies with sonography. AJR 1990 Dec; 155(6): 1277-81. 
5. Davae KC, Sofka Cm, DiCarlo E and Adler RS. Value of Power Doppler Imaging and the hypoechoic halo in the sonographic detection of foreign bodies. JUM 2003, 22: 1309-1313.
 
Follow Up Under local anesthesia, glass pieces were removed surgically from the site of swelling.
 
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