The lymphatic system is anatomically complicated and it is difficult to visualize with current imaging modalities.
Cisterna chyli,
also called “Pequet cisterna” may be recognized on CT scan as a saccular and extended structure (abut 5 cm),
situated in the retroperitoneum,
and it receives the bilateral lumbar lymphatic trunks.
This structure is located in the retrocrural space,
to the right side and behind of the abdominal aorta at the lower border of the T12 or L1-L2 vertebral body.
Literature shows different CT morphologies of cisterna chyli (FIG.4): As a straight thin tube [C] (most frequent),
a straight thick tube [B] or a round/oval structure [A]
It crosses the diaphragm becoming thoracic duct,
the retrocrural space contains also fat,
the Aorta,
the Azygos Vein,
and lymph nodes.
The thoracic duct starts from the cisterna chyli,
at the level of L2-L3, passes through the thorax in the aortic hiatus of the diaphragm.
Toracic duct can be observed and studied through linfography instead of CT scan.
It can be divided in four portions: distally it ascends in the posterior mediastinum,
where it is situated between descending thoracic aorta and azygos vein (FIG.5)
When it reaches the level of T5,
at the third medium,
it gets into superior mediastinum and gradually inclines to the left side.
Proximately,
it passes next to aortic arch anteriorly,
then posteriorly next to the left subclavian artery.
Finally,
the duct terminates by opening into the junction of the left subclavian and jugular veins.
(FIG.6)
Traumatic injuries at L2-L3 level,
with consequent stress of cisterna chyli may cause its breakage with chylous effusion extending both inferiorly,
in retro peritoneal space around the aorta,
the abdominal vessels up to the pelvis,
than superiorly,
defining a chylous leakage through diaphragmatic hiatus with consequent chylo-torax.
Chylo-peritoneum can be observed at abdominal examination,
through the presence of retroperitoneal share of low liquid density which does not increase significantly at the late stages after administration of contrast medium,
and surrounds as a sleeve in cranio-caudal direction the abdominal aorta at level of the kidneys.
Isolated post traumatic lesions of thoracic duct due to recoil or hyperextension of the spine are most frequent at the level of its proximal third,
at its point of passage near aortic root,
is more mobile than the other portions.
The most frequent trauma near to the left subclavian vein tract,
is caused to wrong puncture of the subclavian vein during central venous catheterization procedure.
In both cases,
chylous leakage rising from these districts defines a chylo-thorax originating from the superior-anterior mediastinum.
Negative density (-16,7+8HU),
due to the presence of fat in the context,
is usally observed in almost 4 region of the effusion.
In our experience,
this is the best way to diagnose a chylo-torax