Wikipedia:Osmosis/Lymphedema



Author: Tanner Marshall, MS

Editor: Rishi Desai, MD, MPH, Tanner Marshall, MS

Lymph is the fluid circulating in the lymphatic system, and edema refers to fluid buildup in the body’s tissues,

so lymphedema is a buildup of lymph somewhere in the body’s tissues, typically as a result of some obstruction in the lymphatic system. Alright, so let’s back up and real quick talk about this lymph stuff. So, oxygenated blood gets sent from the heart to your tissues via arteries, which get smaller and smaller until they feed the capillary beds, which then provide nutrients to your cells, as well as pick up waste. And now deoxygenated blood then feeds back into larger and larger veins, and goes back to the heart. Pressure on the arterial side is a lot higher than on the venous side, so as blood comes into the capillary bed from the smaller arteries, called arterioles, the plasma—this colorless, fluid part of blood—is literally forced out into the interstitial space, the space between cells. The majority of that fluid is reabsorbed on the venous side, but typically there’s more forced into the tissue through the arterial side than is taken out by the venous side.

And that’s where the lymphatic system comes into play. All of that excess fluid gets pulled into the afferent lymphatic capillaries, which are these closed-ended vessels found throughout the body—even the brain, which was actually a discovery made in 2015. These lymphatic capillaries also have larger openings than the venous capillaries which means that, in addition to the interstitial fluid, they can accept larger proteins, cellular debris, and even bacteria, which got squeezed out of the arterial side but were too large to get back into the venous capillaries. Once all of that stuff’s the lymphatic system, it’s called lymph. And those afferent lymphatic vessels have one-way valves which, along with smooth muscle contraction, keep the lymph moving along toward the lymph nodes, which have immune cells that once again help filter the fluid, getting rid of potential microbial threats.

The fluid then leaves the lymph nodes and drains back into the systemic veins via the thoracic duct which empties into the left subclavian and jugular veins, and right thoracic duct which empties into the right subclavian and internal jugular veins, and rejoins the blood once again.

So, getting back to lymphedema, when something blocks the normal flow in the lymphatic system, then the lymph gets backed up, which means the interstitial fluid can’t drain properly, and fluid accumulates in the interstitial space. This also means those proteins and cellular debris build up as well, right?

And when all that stuff stagnates, an inflammatory reaction is initiated, which causes macrophages to release inflammatory molecules which ultimately damages surrounding cells and leads to fibrosis, which is this thickening of connective tissue—or scar tissue. This fibrosis causes hardening of the affected area, which is commonly the limbs.

One of the most common global causes of lymphedema is filariasis, an infection with nematode parasites which are these tiny worms, the most common species being Wuchereria bancrofti, Brugia malayi, and Brugia timori. Filariasis happens when one of these nematodes gets in the lymphatic system and causes a bit of fibrosis, both of which create a physical blockage that obstructs the normal flow of lymph. In developed nations, lymphedema is most commonly caused by cancer malignancy and/or its treatment.

This could either mean the lymphatic system itself develops a cancer that causes an obstruction, which is called a primary lymphoma, or it could be a result of metastatic tumor cells from somewhere else that travel to the lymphatic system and cause an obstruction, or it could be the result of cancer treatment—like for example if an affected lymph node or group of nodes are removed via surgery. The most common cancer-associated cause of lymphedema is removal of the lymph nodes as a treatment for breast cancer. All of these causes of lymphedema, you’ll notice, are a result of some other disease, so these are situations that represent secondary lymphedema.

Primary lymphedema, on the other hand, is when there isn’t some other disease or factor that leads to lymphatic obstruction, usually primary lymphedema is a congenital condition that’s been present since birth, maybe as a result of part of the lymphatic system not developing right. For that reason, most people develop primary lymphedema early on, before age 35, which is called lymphedema praecox. When someone that develops primary lymphedema later on, usually after age 35, it’s known as lymphedema tarda. Primary lymphedema is sometimes associated with other genetic disorders as well, like Turner syndrome.

Diagnosis early on is difficult with lymphedema since there aren’t many obvious signs, and can sometimes mimic chronic venous insufficiency, or CVI, where blood collects in the veins, though usually this happens bilaterally, meaning on both sides of the body, as opposed to one side with lymphedema. That being said, sometimes lymphedema can be diagnosed by comparing the affected limb to the opposite limb.

To help out with diagnosis, staging systems are often used, the most commonly used one being defined by the world health organization. During stage zero, the latent stage, there’s some damage to the lymphatics but enough lymph is still being removed, so lymphedema is not present. During stage one, the spontaneously reversible phase, the tissue’s in the pitting stage, where it indents when pressed, and reverses when it’s elevated—also usually the affected area is normal or almost normal size in the morning.

Stage two, or the spontaneously irreversible stage, the tissue takes on a spongy consistency, and is non-pitting, and so it bounces back when pressed.

Also fibrosis starts to develop and the limbs harden and increase in size. Finally, during stage 3 or lymphostatic elephantiasis, swelling becomes irreversible, and the affected limbs are really large and hardened from fibrosis.

Treatment depends on how severe the edema is, and how far along the fibrosis is in the affected limb. People might wear compressive bandages that can help keep fluid from accumulating, as well as compression lymphatic massages to help with lymph flow. If these options don’t work, sometimes people with lymphedema can have surgery to help either improve drainage or reduce fluid load.

All right, time for a quick recap… Lymphedema is a buildup of lymph in the interstitial space as a result of an obstruction in the lymphatic system, which can cause edema, inflammation, and fibrosis in the tissues. Lymphedema can be primary, when it occurs alone, or secondary, when it occurs as a result of another disease like filariasis or cancer. Treatment includes compressive bandages, compression lymphatic massages, and surgery to help either improve drainage or reduce fluid load.