The cisterna chyli: a potential mimic of retrocrural lymphadenopathy on CT scans.

Overview

PURPOSE: To determine the normal appearance of the cisterna chyli and how it may mimic an enlarged retrocrural lymph node on computed tomographic (CT) images. MATERIALS AND METHODS: CT scans were reviewed in 18 patients (17 with cancer, one with benign disease) who had tubular retrocrural structures of attenuation near that of water. The location, diameter, length, CT attenuation, duration of finding, change in size, and the status of intercurrent malignancy were recorded. RESULTS: The cisterna chyli was variably located at T12-L1 (n=11), at T11-T12 (n=5), and at T-12 (n=2). The average length was 3 cm. The average CT attenuation was 12.5 HU. On serial scans in 14 patients, the average change in size was 2.2 mm despite progression or regression of malignant disease at other sites in 11 patients. CONCLUSION: The cisterna chyli can mimic the appearance of an enlarged retrocrural lymph node. Proper identification depends on its characteristic location, tubular configuration, attenuation closer to that of water than soft tissue, and lack of substantial change in size despite changes in disease at other sites.