The authors describe a case of a retroperitoneal bronchogenic cyst in a 36-year-old female. She presented with abdominal pain, nausea, and vomiting. An MRI scan revealed an 8？cm cystic lesion in the left upper retroperitoneum, with intermediate signal on T2-weighted images, high signal on T1 weighted images, and lack of internal enhancement after gadolinium. After laparoscopic excision, the histology findings were compatible with a bronchogenic cyst, which is extremely uncommon in the retroperitoneum. 1. Introduction Bronchogenic cysts are congenital lesions arising from abnormal budding of the embryonic foregut, during early embryogenesis. They develop most commonly in the mediastinum, posterior to the carina [1]. Retroperitoneal location is extremely rare [2]. We report a case of a retroperitoneal bronchogenic cyst, with emphasis on its MRI appearance. 2. Case Report A previously healthy 36-year-old female patient had episodes of abdominal pain in the last three months, associated with nausea and vomiting. Physical examination was unremarkable. Laboratory data showed no abnormalities: transaminases, serum amylase, and lipase were within normal values. An initial ultrasound revealed a large cystic lesion in the left upper quadrant. A contrast-enhanced abdominal MRI was performed, revealing an 8？cm retroperitoneal thin-walled cystic mass, with regular margins, located between the pancreatic tail, the upper pole of the left kidney, and the left adrenal gland. On GRE T1-weighted images (see Figure 1) it had high signal intensity, without demonstration of microscopic fat (no signal dropout in opposed-phase images). It had high signal intensity on T1-weighted images with fat suppression (see Figure 2). On T2 weighted images it revealed intermediate signal intensity (see Figure 3). After intravenous gadolinium injection, fat suppressed T1-weighted images revealed no internal enhancement (see Figure 4). No internal septations or nodules were seen. Figure 1: In-phase T1-weighted (a) and opposed-phase T1-WI (b) transverse images demonstrate a well-defined lesion in the left upper retroperitoneum (arrows), with high signal intensity. The lesion preserved high signal intensity on opposed-phase images, suggesting absence of microscopic fat. Figure 2: Fat suppressed T1-weighted turbo spin echo transverse image reveals high intensity in the lesion (arrow), excluding the presence of fat. Figure 3: Coronal T2-weighted (TR-600？ms; TE-83？ms) MR image shows cyst contents of intermediate signal intensity (arrow). The lesion is located between the pancreatic tail (P), the
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