Retained surgical sponge: diagnosis with CT and sonography.

The diagnosis of a retained surgical sponge was made by CT and sonography in four patients. The plain abdominal radiograph was normal in all cases. In each of four cases of gauze granuloma, CT showed a well-defined round mass with a thick wall; internal heterogeneous densities with a wavy, striped, and/or spotted appearance; mottled calcifications; and gas bubbles. Sonography disclosed a well-defined hypoechoic mass containing highly echogenic foci with a strong posterior shadow. In these cases, CT and sonographic findings, together with a history of surgery, permitted the correct preoperative diagnosis of a retained foreign body.