Two cases of retained foreign bodies after cholecystectomy: diagnosis by sonography, CT, angiography, and MRI.

We encountered two cases of subphrenic abscesses around surgical sponges that had been left at cholecystectomy. These cases had been operated on either eight years or seven years earlier, respectively. These lesions resembled another diseases, especially, liver tumors. In order to make a differential diagnosis, various diagnostic procedures were carried out. Sonography showed a cystic mass with spongiform structures in one case. But in another case, no information of internal structures could be obtained because of the presence of a calcified wall. On CT, the lesions appeared as either round or elliptic masses that contained calcified foci in both cases. Angiography showed the extended and compressed branches of the hepatic artery. Spotty stains were also observed in one case. This appearance resembled a hepatic tumor. MR demonstrated both T1 and T2 elongated masses. The internal structures of the mass were clearly revealed by the improved version of the MR machine. MR proved to be extremely useful in making a differential diagnosis. It is, however, important to evaluate the findings of these imaging procedures synthetically and in association with a careful review of a patient's prior surgical history.