The cisterna chyli is a normal anatomic structure seen as a dilated sac at the lower end of the thoracic duct. Multiple lymphatic channels (namely intestinal, two lumbar and paired descending inter-costal lymphatic trunks) open into this sac. It is located to the right of and slightly posterior to the aorta and anterior to the first and second lumbar vertebrae. About 100 mL of lymph is transported through the channel per hour.
The cisterna chyli is seen in 1.7% of patients evaluated with routine abdominal CT scans and in about 15% of patients evaluated with routine abdominal MR protocols that include highly fluid-sensitive T2-weighted imaging sequences.
Large cisterna chyli – described by some as giant – measures more than 2 cm in transverse diameter. Some of those were shown to exhibit delayed MR contrast enhancement 10 minutes after injection.
Large cisterna chyli may potentially be mistaken for enlarged retro-crural lymph node(s). Good points that help in identification of the cisterna chyli are:
- Characteristic location
- Tubular configuration
- Near-water attenuation value
- Almost no contrast enhancement
- Anatomical continuity with the thoracic duct, and
- Lack of substantial change in size despite changes in disease status at other sites (in case of following up a patient with adenopathy).