Ultrasound for the detection of foreign bodies

Study objective: To determine the ability of an emergency physician to detect a variety of foreign bodies in an experimental model using a portable ultrasound device. Design: Ten pieces of beef were sliced into cubes approximately 6 cm on each side. Six different groups of foreign bodies were examined: gravel, cactus spine, glass, metal, wood, and plastic. An independent observer placed the objects in a random fashion into the beef cubes. One hundred twenty observations were made using sets of ten beef cubes at a time. Five foreign bodies were placed into each set of ten beef cubes. Interventions: A blinded emergency physician used a portable ultrasound with a 7.5-MHz transducer to determine the presence or absence of a foreign body in each cube. Measurements and main results: Ultrasound detected 59 of 60 foreign bodies, including all cubes of meat embedded with gravel, cactus spine, plastic, metal, and wood. Glass was detected nine of ten times. Of the 60 cubes of meat with no foreign bodies, one false-positive was recorded. This yielded sensitivity, specificity, positive predictive value, and negative predictive value of 98%. Positive determinations by ultrasound were significantly greater in the meat cubes with foreign bodies compared with the control group with no foreign bodies (P < .001 by χ²). Although the subset of glass foreign bodies had one false-positive and one false-negative, it was not significantly different in comparison with the other groups (P > .05 by χ²). Conclusion: Ultrasound has promise as a diagnostic tool for the detection of a variety of foreign bodies. Further clinical studies using ultrasound for the detection of foreign bodies are warranted.