Introduction Retained surgical sponges or so-called textilomas pre- sent a diagnostic problem associated with possible med- icolegal consequences. Retroperitoneal textilomas rep- resent less than 17 % of intra-abdominal textilomas [1], whereas the incidence of retained foreign bodies has been estimated at 1 per 1000–1500 laparotomies [2]. The clinical presentation of textilomas is highly vari- able, ranging from merely an incidental observation to severe postoperative complications [2]. The MR appear- ance of retroperitoneal textilomas has not been previ- ously described and spontaneous modifications of their aspect over years has not been documented on serial CT studies. The purpose of this report is to document the MR appearance and the serial CT aspects of a texti- loma caused by a retained surgical sponge, which mim- icked a pseudocystic mass of the renal fossa. Case report In January 1990 a 38-year-old man underwent explor- atory renal surgery in another institution and a periop- erative renal biopsy for a suspected renal tumor which proved to be a hypertrophic column of Bertin. He made an uneventful recovery. In March 1991 an ultra- sound study revealed a 5-cm perirenal mass with a het- erogeneous and mainly hypoechoic aspect (Fig. 1). Some irregular internal echoes were noted; posteriorly, the mass showed acoustic shadowing. The patient was admitted. He was afebrile and appeared to be in good health. Plain radiographs of the abdomen were normal. A CT scan of the abdomen confirmed the presence of a suprarenal mass. On unenhanced CT images, the mass appeared heterogeneous with a peripheral hyperdense wall and irregular hyperdense internal areas (Fig. 2). It had well-defined limits and was located below the left adrenal, at the upper pole of the left kidney without a clear cleavage plane. An MR examination was perform- ed on a 0.5-T superconducting unit. Coronal T1-weight- Eur. Radiol. 8, 57–59 (1998) Ó Springer-Verlag 1998 European Radiology Case report Perirenal textiloma: MR and serial CT appearance M.-F. Bellin 1 , B. Hornoy 1 , F. Richard 2 , C. Davy-Miallou 1 , Y. Fadel 1 , S. Zaim 1 , E. Challier 1 , Ph. Grenier 1 1 Department of Radiology, Hoˆ pital Pitie´ -Salpeˆ trie` re, 83 Bld. de l’Hoˆ pital, F-75 651 Paris Cedex 13, France 2 Department of Urology, Hoˆ pital Pitie´ -Salpeˆ trie` re, 83 Bld. de l’Hoˆ pital, F-75 651 Paris Cedex 13, France Received 31 December 1996; Revision received 14 March 1997; Accepted 17 March 1997 Abstract. We describe changes in imaging features of a textiloma (retained surgical sponge or retained for- eign body) left in the renal fossa after exploratory re- nal surgery. One year after the initial surgery, the MR aspect of the textiloma was not specific, with a homo- geneous low signal intensity on T1-weighted images. Serial CT examinations over 4 years demonstrated progressive growth and calcification of the mass which appeared pseudocystic with a peripheral in- flammatory wall. Granulomas caused by a retained surgical sponge should be considered as a cause of retroperitoneal mass in patients with a history of pri- or surgery. Key words: Foreign bodies – Textiloma – Surgery complications – Medicolegal problems – CT – MR imaging Correspondence to: M.-F. Bellin Fig. 1. Sagittal sonogram demonstrates a hypoechoic pararenal mass (arrows). The mass contains peripheral and internal echoes with posterior acoustic shadowing