Conditions: Chyle Leak
Fluid (and particles such as proteins and sometimes whole cells) from outside the body’s cells drains into lymphatic capillaries (small lymphatic channels).
Lymphatic capillaries join, forming larger lymphatic vessels.
What is chyle?
Chyle, consisting of long chain triglycerides from the gut and fluids, particles, and some cells from throughout the body, collects in a series of merging channels, eventually becoming the main channel, the thoracic duct, which feeds chyle into the blood stream at the left and right subclavian veins at the junction between the neck and the chest. Click on the image to enlarge it.
Chyle is a type of fluid running between lymph nodes in a series of vessels separate from veins and arteries. Chyle is a milky fluid consisting of certain fats absorbed from the gut (long chain triglycerides) mixed with fluid, particles, or occasionally cells shed into the chyle drainage system throughout the body. General dietary fats have both medium and long chain triglycerides in them. Medium chain triglycerides are absorbed from the gut directly into the bloodstream, whereas long chain triglycerides move from the gut to the lymphatic system before feeding into the bloodstream where the thoracic duct reaches the subclavian vein. The lymphatic channels are like street gutters, collecting the overflow fluid and debris from the spaces between cells. The chyle channels merge in a pattern like a series of small rivers joining to make a larger river. The larger lymphatic vessels transport the chyle to the thoracic duct where it is emptied into the bloodstream at the subclavian veins.
What is chyle leak?
When the tube (vessel) carrying the chyle ruptures, chyle can leak to the surrounding tissue. This is similar to bleeding— when a blood vessel breaks, and blood leaks. Most chyle channels are very small, and any surgical incision through them has a minimal leak of chyle that is not noticeable and heals without problem. If a larger lymphatic veseel were to leak, especially if it were to do so in a space that has potential to expand and collect chyle, this would be a clinically significant chyle leak. In contrast to blood, which clots into a solid when it leaks outside of a blood vessel, chyle does not clot, so a leak may persist until surgically corrected or spontaneous healing occurs.
Why is a chyle leak a problem?
Since chyle is a valuable fluid, both from an immune system sense and for the nutritional role of fats, a leak and loss of chyle may affect immune strength and nutrition. Another reason why a significant chyle leak can be problematic is that a collection of chyle may delay healing of a wound as well as compress the nearby tissues (such as lung), making them work less well.
What causes a chyle leak?
Almost every surgical operation deeper than skin causes at least some chyle leak (technically) because the small lymphatic vessels cannot be seen. Surgery requiring dissection around the larger lymphatic vessels is a risk factor for chyle leak. Sometimes, if a chyle leak is identified during surgery, it may be ligated (repaired) at that time. Penetrating trauma may also cause a chyle leak.
How is a chyle leak identified?
Since patients are routinely required to have an empty stomach before surgery, chyle fluid has no fat (specifically long chain triglycerides) in it. While this is an appropriate safety measure, chyle without long chain triglycerides is colorless, making identification of a chyle leak much less obvious than blood leaking from a blood vessel. A surgeon may observe a chyle leak in the same operation in which the leak occurred by observing a flow of clear liquid from a site in the surgical bed, which may be more likely in areas where larger chyle channels, such as the thoracic duct, are likely to be found. If not identified during the initial surgery, a chyle leak typically presents after surgery when a patient begins to eat food with some fat in it, which increases the volume and flow of chyle. At the leak site, a fluid collection in or near the surgical wound may occur, and if a surgical drain is in place, the drain fluid may increase in volume and change color to a milky white.
How is a chyle leak treated?
Small chyle leaks may heal spontaneously without intervention, or with a diet containing fat only of medium chain triglycerides. Larger chyle leaks may require a surgical procedure to identify the leaking lymphatic vessel and ligate (close) it. The technique of return to the operating room for identifying the site of a chyle leak varies, but one technique involves intentionally feeding the patient a fatty diet (like whole whipping cream) before this particular operation, in variance with normal empty stomach guidelines, so that chyle is a more visible during surgery. Lymphoscintigraphy is another, more involved, way to identify the site of a chyle leak, where a type of dye is injected into the lymphatic system traced to the leak site. The dye itself might close the leak, but if not, surgery directed at the demonstrated site of leak may then follow.