The purpose of this study was to determine the prevalence and characteristics of the cisterna chyli (CC) in a large 3,000-patient cohort and to identify potential predisposing factors for the development of a CC. Three thousand consecutive contrast-enhanced CT examinations (1,261 women, 1,739 men, mean age 61.0 years) of the chest and/or abdomen were included in this retrospective study. Imaging characteristics of the CC (size, attenuation, location) were documented as well as clinical information (malignant disease, pattern of metastasis). A CC was found in 16.1% of the patients with an average volume of 302 microl. The mean attenuation was 4.8 Hounsfield units (HU). Twenty percent of the CC showed CT densities of 15 HU and higher. Patients with malignancies showed a significantly (p < 0.001) higher prevalence of CC (340/1,757, 19.4%) than patients with benign conditions (144/1,243, 11.6%). Especially the finding of a large CC (>1,000 microl) represents an elevated relative risk for malignancy of 1.7 (p = 0.0017). We found a significant association between malignant disease and the presence and size of a cisterna chyli. Identifying the continuity between the CC and the thoracic duct is a safer method to distinguish a CC from retrocrural lymph nodes than near-water CT attenuation alone.

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