Introduction Duplication of the gastrointestinal tract (GI) is a rare congenital anomaly which can occur in any segment of the alimentary tract [1–4]. By definition, they are lo- cated in or adjacent to the wall of the GI, have smooth- muscle tissue in their walls and are lined by alimentary tract mucosa [3]. Morphologically, they may be spheri- cal or tubular; may or may not communicate with the or- gan of origin to whose mesenteric fold they are closely connected [2–4]. Thoracoabdominal GI duplications are a rare, but distinct, variety of tubular duplications which arise in the abdomen, pass through the diaphragm and can produce symptoms secondary to its mass effect in the posterior mediastinum [3–6]. We report a case of a thoracoabdominal duplication cyst in a 7-month-old girl and illustrate the US, CTand MR appearances. Case report A 7-month-old girl was sent to our department for in- vestigation of abdominal distention and a palpable mass. A firm and nontender mass was palpated in the left epigastrium. Stool test was positive for blood. An abdominal US examination revealed two cystic lesions: one in the mediastinum 5 × 5 × 5 cm sized, left to the midline; the other 8 × 10 × 10 cm sized, in the left upper quadrant of the abdomen posterior to the stomach. They were connected to each other with a narrow lumen passing through the diaphragmatic hiatus (Fig.1). Post- contrast CT scan of the thorax and upper abdomen was compatible with the US findings (Fig. 2). An MR exami- nation was performed using a body coil. On coronal and sagittal spin-echo images, the anatomical relationship of the cysts with the diaphragm and each other was demon- strated (Fig. 3). The cyst content had hypointense signals on T1- and hyperintense signals on T2-weighted images showing its high water content. Surgery revealed two cysts, one located posterior to the stomach and the other left to the oesophagus in the mediastinum connected to each other with a narrow lu- men compatible with radiological findings. The cysts having a common muscular wall with stomach and oe- sophagus were excised leaving intact muscular layer at the visceral side (Fig. 4). No luminal communication be- tween the duplication and the stomach or the oesopha- gus was detected. The pathological examination of the specimen displayed a cyst wall which was lined by sin- gle-layered columnar epithelium and some mature chondroid elements were found showing that it also had bronchogenic origin. D iscussion Gastrointestinal duplications can occur anywhere in the alimentary tract [1, 3, 7]. The most common site is the ileum [4]; next, in order, are the oesophagus, jejunum, colon, stomach and appendix. They are named accord- Eur. Radiol. 7, 382–384 (1997)  Springer-Verlag 1997 European Radiology Case report Thoracoabdominal duplication cyst: U S, CT and MR findings G. Savci 1 , E. Balkan 2 , T. Ozyaman 1 , H. Dogruyol 2 , E. Tuncel 1 1 Department of Radiology, Uludag University Medical School, Gorukle Campus, TR-16059 Gorukle, Bursa, Turkey 2 Department of Pediatric Surgery, Uludag University Medical School Gorukle Campus, TR-16059 Gorukle, Bursa, Turkey Received 6 November 1995; Revision received 5 January 1996; Accepted 2 February 1996 Abstract. A rare case of thoracoabdominal duplica- tion is reported. Radiological workup including US, CT and MR provided the correct diagnosis. The US revealed the cystic nature of the lesions, whereas CT and MR showed their relationship with the dia- phragm and each other. Coronal- and sagittal-plane MR images were helpful in demonstrating the exten- sion of the lesions. The patient was discharged after an uneventful surgery and recovery. The histological evaluation revealed the cyst lined with single-layered columnar epithelium and the cyst wall contained sub- mucosal mucous glands with underlying smooth mus- cle and also some mature chondroid elements with bronchogenic origin. Radiological findings and differ- ential diagnosis are discussed. Key words: Stomach – Duplication cyst – Congenital anomalies – Gastrointestinal tract duplication – Oe- sophagus Correspondence to: G. Savci