MR findings of surgically retained sponges and towels: report of two cases.

MR findings of surgically retained sponges (gossypiboma) in two patients are reported. The sponges were well-encapsulated round masses with a thick wall of low signal intensity on both T1-weighted images (T1WI) and T2-weighted images (T2WI). The signal intensity of the center of the masses varied in both patients on T1WI and T2WI. In one patient, the mass was high in signal intensity on both T1- and T2-weighted images and had a low signal intensity whirl that represented a surgical sponge. The sponge was rich in serosanguinous fluid with a high protein concentration (8.2 g/dl). In the other patient, the mass was low in signal intensity on both T1- and T2-weighted images, and was mainly composed of organized cotton matrix with little fluid. The protein concentration of the fluid was lower than in the former case (6.4 g/dl).