Cisterna chyli at routine abdominal MR imaging: A normal anatomic structure in the retrocrural space

The cisterna chyli, a dilated lymphatic sac in the retrocrural space, represents the origin of the thoracic duct. It is seen in approximately half of lymphangiographic studies and 20% of autopsies. Highly fluid-sensitive magnetic resonance (MR) imaging sequences such as single-shot rapid acquisition with refocused echoes, which are currently used in many abdominal MR imaging protocols, frequently result in the depiction of this structure. The cisterna chyli was evident on abdominal MR images acquired in 30 (15%) of 200 consecutive patients who underwent MR imaging at the authors' institution between February and June 2002. Its appearance varied from that of a thick tube to that of a thin tube, parallel or converging tubes, tortuous tubes, a sausage-shaped fluid collection, a focal collection, or a focal plexus. Radiologists who perform MR imaging should be familiar with the various possible appearances of this normal anatomic structure so as not to mistake it for a pathologic entity.