Imaging Studies
Soft tissue radiographs are indicated as the initial study modality when attempting to exclude retained foreign bodies. Most calcareous spines are visualized either directly or indirectly with the use of radiographs. Nonradiodense objects can be revealed as filling defects or outlined by air drawn into the wound during the injury.
If an object cannot be visualized by plain radiography or retrieved easily through direct visualization, ultrasound may be used. Ultrasound can detect nonradiodense foreign bodies as small as 1 X 2 mm and can be used to accurately localize foreign material and provide guidance during removal. Tendons, deep scar tissue, fresh hematoma, and tissue calcifications can produce false-positive ultrasound readings. Ultrasonography requires experience and skill to maximize its usefulness.
Computed tomography (CT) scans and magnetic resonance imaging (MRI) are expensive alternatives to ultrasound that can identify and precisely localize retained foreign material. Both require a high degree of patient cooperation and may be difficult to perform on pediatric patients.
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Echinoderm envenomations. Close-up of brittle star arm. Although spiny, members belonging to this class (Ophiuroidea) generally are considered harmless. Of the phylum Echinodermata, only starfish (class Asteroidea), sea urchins (class Echinoidea), and sea cucumbers (class Holothuroidea) are capable of envenomation. Photo courtesy of Scott A. Gallagher, MD.
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Echinoderm envenomations. Unlike most starfish that are typically pentamerous, the crown-of-thorns starfish (Acanthaster planci) may have as many as 23 arms and a body disc up to 60 cm in diameter. Photo courtesy of Dee Scarr.
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Echinoderm envenomations. Detail of the crown-of-thorns starfish (Acanthaster planci) spines, which may grow to 6 cm in length. Photo courtesy of Dee Scarr.
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Echinoderm envenomations. Detail of the crown-of-thorns starfish (Acanthaster planci). Photo courtesy of Scott A. Gallagher, MD.
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Echinoderm envenomations. The common and toxic sea cucumber, Bohadschia argus, with extruded Cuvierian tubules. Contact with these sticky white tentaclelike organs or their free-floating fragments may result in intense skin or ocular irritation. Photo courtesy of Paul S. Auerbach, MD.
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Echinoderm envenomations. Long-spined sea urchins, such as this Diadema species, inflict an acutely painful penetrating injury that may be accompanied by systemic symptoms and chronic wound sequelae. Photo courtesy of Dee Scarr.
