Treatment of lymphedema (1. What is edema?: the difference between the blood vascular system and the lymphatic system)

We periodically provide the information on basic knowledge and treatment of lymphedema as well as the current findings and global trends.

1. What is edema?: the difference between the blood vascular system and the lymphatic system

The artery/vein and lymphatic vessels play a primary role in circulation of body fluid in humans. They are called the blood vascular system and lymphatic system, respectively.
In the blood vascular system, after arterial blood enters the capillaries, about 90% of arterial blood directly flows into the veins, and circulates in the body. You may know this because you have learned that "the artery is the vessel with clean blood pumped from the heart, and the vein is the vessel with dirty blood returning from the whole body to the heart", at school.


Meanwhile, in the lymphatic system, about 10% of body fluid that did not returned to the veins (capillary veins) becomes interstitial fluid, and is absorbed into the lymphatic vessels in the whole body. The absorbed interstitial fluid is lymph fluid. As lymph fluid repeatedly joins together through the lymphatic vessels, it goes back to near the heart as well as vein blood. Furthermore, lymph fluid flows into the veins at the "venous angle" near the heart, and returns to the circulation of body fluid. The flow volume of lymph fluid is about 1 L/day in an adult, and plays an important role in the circulation of body fluid.


Although "swelling" and "edema" are used to show changes occurring in the body surface, they are totally different medical conditions. You can easily understand them if you know the difference between the blood vessel system and lymphatic system above mentioned.

"Swelling": The condition in which blood constituent is accumulated outside the blood vessels with the volume increased. This condition is called "swelling" as a medical term.
"Edema": 1) The condition in which circulation function of the blood vessel system/heart or urinary function of the kidneys deteriorates, and the body is enlarged by accumulated fluid. 2) the condition in which excessive lymph fluid is not recovered and is accumulated outside the lymph, leading to the enlarged body. These conditions are called "edema" as a medical term.

Although various factors may cause swelling or edema, surgery or treatment of cancer can decrease lymph function, resulting in edema of extremities. This is called lymphedema (after surgery of cancer).


The next column will explain lymphedema in detail.