Lost in the Woods: A Case Report of a Radiolucent Wooden Foreign Body in a Child After Negative CT, Detected on Repeat Ultrasound.

Retained soft-tissue foreign bodies are a common but often missed complication of traumatic wounds, particularly when composed of radiolucent materials such as wood, which can evade detection on standard imaging. Although radiography and computed tomography (CT) are highly sensitive for radiopaque objects, they may fail to identify organic foreign bodies. This makes timely diagnosis challenging and underscores the importance of ultrasound when the mechanism suggests wood. A previously healthy five-year-old boy presented to a community emergency department after sustaining a puncture wound to the right thigh from a tree branch, with localized tenderness but no obvious foreign body on examination. Plain radiographs of the femur and pelvis and a CT of the pelvis demonstrated subcutaneous air but no retained foreign body; the wound was explored and irrigated, and the patient was discharged on oral antibiotics. He then presented to a children's hospital with worsening pain, erythema, and purulent drainage. Initial ultrasound showed a small, heterogeneous subcutaneous collection concerning for an abscess, and he improved transiently with intravenous, then oral, clindamycin. Within 24 hours, he returned with recurrent pain, and repeat ultrasound revealed a linear echogenic structure within the deep subcutaneous tissue consistent with a wooden foreign body, associated with an adjacent abscess. Operative exploration led to the removal of a 6-cm piece of tree branch from the thigh, with subsequent uncomplicated recovery. This case illustrates that CT may not exclude a retained wooden foreign body when the mechanism of injury strongly suggests organic material. In patients with persistent pain, swelling, drainage, or recurrent symptoms, repeat targeted ultrasound should be considered even after initially negative imaging.