Sonographic appearance of a retained surgical sponge in the neck

We report the sonographic appearance and clinical course of a retained surgical sponge in the neck beginning 6 months after a partial thyroidectomy. Sonograms showed a subcutaneous curvilinear hyperechoic interface with marked acoustic shadowing obscuring the left side of the neck. Three months later, a fistulous tract could be seen. Surgical exploration revealed a florid foreign tissue reaction due to a retained surgical sponge. Early diagnosis of retained sponges is important to enable expeditious removal before complications develop.