CT features of a pericardial gossypiboma

We report a case of surgically retained pericardial sponge as a cause of paracardiac mass in a woman who had thoracotomy 3 weeks prior for replacement of mitral valve prosthesis. Computed tomography examination showed a thin-walled mass containing relatively high-density material in the central part with low-density rim at the periphery suggesting a haematoma with clot formation at first. Surgically removed mass was a retained sponge between right atrium and pericardium. Gossypiboma should be included in the differential diagnosis of an intrathoracic mass besides haematoma and abscess formation in any patient who has had previous thoracotomy.