Accuracy of ultrasonography in detecting radiolucent soft-tissue foreign bodies

Detection of radiolucent soft-tissue foreign bodies is a challenging problem, which is especially further complicated when retained foreign body is highly suggested by clinicians but radiography is negative. So, blind exploration is sometimes hazardous for patients. The purpose of this study was to determine the accuracy of ultrasonography (USG) in detecting radiolucent soft-tissue foreign bodies in the extremities.

From November 2011 to January 2012, patients with clinically suspected radiolucent soft-tissue foreign body and negative radiography were evaluated by USG with a 12-MHz linear array transducer. The patients with positive clinical and USG examination were included in our study and underwent exploration or USG removal.

Fifty-one patients underwent foreign body removal under ultrasonography-guided or surgical exploration and 47 patients had foreign body (31, 12, 3, and 1 case had thorn, wood, glass, and plastic, respectively). Ultrasound was positive in 50 patients. USG falsely predicted the presence of foreign body in four cases and was falsely negative in one of the cases. Accuracy, sensitivity, and positive predictive value were determined as 90.2%, 97.9%, and 92%, respectively.

The real-time high-frequency USG is a highly sensitive and accurate tool for detecting and removing radiolucent foreign bodies which are difficult to be visualized by routine radiography.