Retained foreign bodies are associated with up to 1.9% of wounds.1 The presence of a foreign body in a wound increases the incidence of a wound infection.2 Retained foreign bodies are a major cause of litigation against Emergency Physicians.3,4 A high index of suspicion for a retained foreign body must be maintained whenever there is the potential for a foreign body in a wound.5-7 This chapter focuses on the identification and removal of subcutaneous foreign bodies using bedside Emergency Department ultrasound (US).
Foreign bodies may be small, leave no skin entry marks, and consist of many different types of material. Almost any object (i.e., solid, liquid, or gas) can become a foreign body and present itself in a location where it should not reside. Standard plain radiographs and fluoroscopy are good at identifying radiopaque objects (e.g., metal, gravel, and glass).8-14 Glass accounts for up to 50% of missed foreign bodies using the physical examination and radiographs.15 The ability of techniques to identify a foreign body vary by the size and composition of the foreign body.10 Magnetic resonance imaging (MRI) and computed tomography (CT) are useful to detect foreign bodies.13,16,17 These are expensive imaging modalities and the images vary depending on the length of time the foreign body has been present.17 Certain foreign bodies may produce artifacts that diminish the MRI and CT image qualities.13 Plastic, hair, vegetative material, and rubber are not radiopaque and are not routinely identified on plain radiographs.6,8,9,11-14,18-20 US identifies radiopaque foreign bodies. US can detect foreign bodies that are not radiopaque due to their different echotexture in relation to surrounding structures.6,9,16-33 The sensitivity and specificity of US in detecting retained soft tissue foreign bodies have been reported as 72% and 92%, respectively.15 Subgroup analysis of radiolucent or wooden foreign bodies demonstrated a sensitivity of 96.7% and specificity of 84.2%.15 US can detect foreign bodies that are very small.34
ANATOMY AND PATHOPHYSIOLOGY
Foreign bodies can be present in almost any part of the body. Foreign bodies can be detected with US in nontraditional places. They have been identified in the eye, esophagus, and tongue using US.32,35,36 Foreign bodies isolated to small spaces (e.g., the web spaces of the hand) may not be identified due to the size of the US transducer footprint and an anatomic location that is difficult to scan.29
Not diagnosing foreign bodies can be dangerous for the patient and lead to an increased risk of complications. Legislation to introduce an aluminum penny into circulation in the United States in 1973 was defeated in part by Pediatricians’ and Pediatric Radiologists’ concern that these new coins would not be easily identified on plain radiographs....