What Is the Cisterna Chyli? Where It Is and What It Does
The cisterna chyli is a small sac at the bottom of the thoracic duct, your body’s largest lymph vessel. It sits deep in the abdomen, in front of the spine around the first and second lumbar vertebrae (L1–L2), and collects lymph from your legs, pelvis and digestive organs before that fluid travels up through your chest and back into your bloodstream.
An older version of this post called the cisterna chyli the body’s largest lymph node. That was wrong. It’s a collecting sac, not a node, and we’ve rewritten the post to get it right.
What does “cisterna chyli” mean?
Cisterna is Latin for a reservoir or tank. Chyli means “of chyle,” the milky fluid that forms when your small intestine absorbs fat from food into the lymph. So the name translates to “cistern of chyle.” You’ll also see it called the chyle cistern or the receptaculum chyli.
Where is the cisterna chyli?
Deep at the back of the abdomen, behind the lining of the abdominal cavity
In front of the spine, usually around L1–L2, though it can sit a little higher
Right beside the aorta, the body’s main artery, on its right side and slightly behind it, tucked behind the part of the diaphragm that anchors to the spine
It also varies more than most textbook diagrams suggest. A 2024 review of anatomy studies found a distinct cisterna chyli in only about half of people. When there isn’t one, the lymph trunks join through a looser network of small channels instead. When it is there, it’s small: about 2 centimeters (under an inch) long on average.
What flows into it?
Lymph reaches the cisterna chyli through a few large lymph trunks:
The lumbar trunks bring lymph from your legs, pelvis, kidneys and much of the abdominal wall.
The intestinal trunk brings lymph from your digestive organs, including chyle from the small intestine.
By the time lymph arrives, it has already passed through lymph nodes along the way.
Where does the lymph go next?
From the cisterna chyli, lymph flows up the thoracic duct, which passes through the diaphragm and runs up through the chest alongside the spine. At the base of your neck on the left side, the duct empties into your bloodstream where two large veins meet (the left internal jugular and left subclavian veins).
The thoracic duct drains most of the body: both legs, the abdomen, the left side of the chest, the left arm, and the left side of the head and neck. The right arm and the right side of the head, neck and chest drain through a smaller channel on the right side.
What the cisterna chyli does, and what it doesn’t
What it does: it’s a collection point. It gathers lymph from the lower body and the gut and passes it into the thoracic duct. Because chyle travels this route, it’s part of the path most of the fat you eat takes to reach your bloodstream.
What it doesn’t do: it isn’t a lymph node, and it doesn’t filter lymph. Filtering happens in lymph nodes, the small, bean-shaped structures lymph passes through on its way to the trunks. Lymph nodes are also where many of your immune cells gather.
How does lymph move without a pump?
Your heart pumps blood, but lymph has no pump of its own. It keeps moving because:
the walls of larger lymph vessels contract in a slow rhythm
one-way valves inside the vessels stop it flowing backward
your muscles squeeze nearby vessels when you move
breathing changes the pressure in your chest and belly, which helps draw lymph up the thoracic duct
Where HOT HAVEN fits in
We’re a sauna and lymphatic compression studio in downtown San Diego, not a clinic, so we don’t make claims about what our sessions do inside your body. Our lymphatic compression session is a hands-free 55 minutes in a full-body compression suit that covers your legs, hips and midsection, and arms. The suit gently inflates and releases in waves while you rest, and we can adjust the pressure for you. You may also see it called pneumatic compression or pressotherapy.
You can also make it the first half of our Haven Ritual: lymphatic compression first, then the infrared sauna.
If you’re pregnant, have a medical condition, are recovering from surgery, or aren’t sure whether compression is right for you, check with your healthcare provider before booking, and let our front desk know when you book.
First time with us? Your first session is $50. Book your session