The cisterna chyli: incidence and characteristics on CT.

The objective of this study was primarily to determine the incidence of the cisterna chyli (CC) on computed tomography (CT). Its radiologic characteristics were also evaluated. Retrospective review of 403 randomly chosen CT cases was made. All patients received intravenous contrast. Note was made of incidence, location, size, attenuation values, slice thickness, age, sex, and the presence or absence of malignancy or adenopathy. There were seven cases of demonstrated CC (1.7%). It was variably located at the L2 to T11 levels; average attenuation was 4 H and average size was 7.4 mm AP by 7.0 mm in transverse diameter with rounded to elliptical shape. Average length of CC was 1.5 mm. Malignant primary was present in four of the seven cases, and none of the seven had adenopathy. There were three males and four females; average age of the CC group was 55.5 years. Visualization of the CC on CT is not rare (1.7%); as previously reported, it should be distinguished from retrocrural adenopathy by its low water attenuation, anatomic continuity with the thoracic duct, tubular nature, and lack of intravenous contrast enhancement.