In prior posts, I’ve talked about the difference between edema and lymphedema (click here & here to see those posts). Today, let’s take a look at conditions that begin as edema & can become lymphedema as the swelling persists. How can that happen?
To understand how edema can become lymphedema, we need to revisit what lymphedema is. By definition, true lymphedema is an accumulation of protein-rich fluid (tissue which has excess protein in it). How does protein get into fluid? You eat protein (like meat, eggs, etc.), but your body also makes proteins that play an essential role in bodily function. I won’t get into the bio-physiology of proteins except to comment on one: a plasma (blood) protein called albumin.
Albumin helps regulates which way fluid goes, into the blood vessels or into the tissue to potentially cause swelling (known as “colloid osmotic pressure”). Albumin, which is made by the liver, accounts for 70% of the colloid osmotic pressure.1,2 That’s huge!
Second, by definition, true lymphedema is the result of damage to the lymphatic system. How does the system get damaged? Genetic causes (called primary lymphedema) or trauma (called secondary lymphedema). Trauma is the most common. Chronic edema can be considered trauma because it increases the amount of fluid the lymphatic system must transport out of your tissue & back to the heart over time (sort of like abusing the lymphatic system).
Your lymphatic system has a pump, little “hearts” called lymph angions. Just as your heart pumps blood, these angions pump lymph fluid. But while the heart is a closed, circulatory system, the lymphatic system carries fluid one way, from the tissue spaces (throughout the entire body) to the heart. Just as blood enters the heart, stretching the wall of the right atrium & causing it to contract, fluid enters a lymph angion, stretching its wall & causing it to contract. At rest, contractions are 6-10 times per minutes. When necessary, this pumping can increase up to 20 times per minute.4 However, just like with the heart, such endurance cannot be sustained indefinitely. The lymph angion will fail & stop working. 5 When that happens, the lymphatic load remains in the tissue causing inflammation & scarring. This leads to an important point:
Lymphedema is not reversible once damage has occurred because of the mechanical, structural changes that have taken place. Progression of the condition can be stopped & symptoms can be improved, but the anatomy cannot be like it was before the damage.
In acute injury or initial trauma, edema is present & the lymphatic system is pumping as hard as it can to remove the excess fluid. The body usually recovers, the swelling inundation subsides & the lymphatics return to normal. But over time (such as with chronic edema), the lymph system becomes overwhelmed & eventually stops working. When that happens, inflammation & scarring occur. The system becomes mechanically & structurally damaged in the area of congestion.
Now that we’ve reviewed what lymphedema is, what are some causes of chronic edema & why can they cause secondary lymphedema?
Obesity, lipedema & other fat disorders
These conditions slow down the flow of lymphatic fluid. I often use the analogy of driving around a mountain. Because of the curves & narrow roads, you have to slow your speed. When there are several cars, congestion results. When lymphatic vessels must weave through fat tissue, lymph fluid can become sluggish & congestion results, creating a backup of fluid which can lead to scarring of the lymphatic vessels.
Additionally, fat (or adipose) causes inflammation itself & inflammation can cause more fat development. Inflammation is the body’s response to trauma which increases blood flow to the affected (which increases swelling in that area). The cycle continues.
Venous pressure causes an increase in the lymphatic load. Conditions such as chronic venous insufficiency or varicose veins are conditions which cause blood flow to regurgitate in the lower legs instead of efficiently making its way northward to the heart.
Another source of increased venous pressure is positioning. Feet remaining in a dependent position (hanging down) for extended periods such as jobs requiring long episodes of standing or sitting create significant pressure in the lower legs that must be overcome. Both the amount and speed of blood flow decrease in the legs after 15 minutes of static, dependent positioning.6
Another source of venous pressure is inactivity or not contracting muscles (even if in a gravity neutral position) as is seen in paralysis after spinal cord injury or a stroke. The lymph system is not able to overcome the increased tissue pressure in these cases & eventually fails, leading to scarring.
Conditions such as heart failure, kidney failure, thyroid impairment & liver disease all can create an excessive amount of fluid7 & an inability of the lymph system to keep up with the demands, resulting in fatigue & eventual scarring of lymphatic vessels.
Localized infection such as cellulitis (particularly when repeated infections occur) result in scarring of lymphatic vessels.
Diabetes causes changes in the smallest parts of your blood vessels (making up the capillary beds). The capillary bed wall thickens & enlarges, allowing the exit of blood matter (water, proteins & other molecules) that would not otherwise exit. That creates an added burden for the lymphatic vessels to manage. 8 Additionally, in my own thinking, because this results in loss of blood flow to other areas, it may likely cause disease of lymphatic vessels themselves. Either case would eventually cause scarring.
One of roles of the lymphatic system includes maintaining homeostasis (preventing swelling). Anything that causes edema creates more work for the lymphatic system. And when you work, work, & work more without rest, you get tired. So does your lymphatic system. When the lymphatic system gets tired, the fluid, protein & other molecules it’s responsible for get left in the tissue. That causes an inflammatory response which creates a cascade of events that create a cycle of chronic inflammation & scarring called lymphedema. As the cycle continues, you begin to see the symptoms of lymphedema. In all the cases mentioned above, lymphedema occurs as a result of structural, mechanical damage to the lymphatic vessels, rendering it ineffective as a result of being overtaxed.
What can you do to prevent lymphedema resulting from chronic edema? Manage your health condition &, if your doctor approves, get compression. Check out past blogs for posts on compression!
1 https://www.ncbi.nlm.nih.gov/books/NBK531504/, https://en.wikipedia.org/wiki/Oncotic_pressure
4 Weissleder, H., Schuchhardt, C. (2008). Lymphedema Diagnosis and Therapy (4th ed.), p.36. Germany: Viavital Verlag GmbH.
5 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 201. Germany: Urban & Fisher.
6 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 434. Germany: Urban & Fisher.
7 Foldi, M, Foldi, E. (2006). Foldi’s Textbook of Lymphology (2nd ed.), p. 242-259, . Germany: Urban & Fisher.