3.Progress of lymphedema and degeneration of lymphatic vessels
As mentioned in the previous column, lymphedema is a condition in which lymph fluid is accumulated in the interstitium due to stagnation of lymph flow. Also, it has a refractory nature, and causes disorders due to various conditions including not only changes in thickness of the extremities by edema but also inflammation/infection. Many cases are secondary lymphedema after cancer treatment. It is important to understand changes in lymphatic vessels caused by stagnated lymph flow.
Removal of lymph nodes results in obstructing and stagnating lymph flow around the lymph nodes. As a result, the increased inner pressure of the lymphatic vessels dilates the lymphatic vessels. The continued condition strains the lymphatic vessels, causing degeneration.
The next paragraph explains the degeneration using two keywords of 1) smooth muscle and 2) endothelial cell.
The outer layer of the thick lymphatic vessels consists of smooth muscle. In general, the smooth muscle causes peristaltic motion of lymphatic vessel, leading to active transport of lymph fluid against gravitational force. However, if the inner pressure of the lymphatic vessels continues to increase, transformed smooth muscles increase and thicken, resulting in gradually narrowing of the lumen.
In the inner layer of lymphatic vessels, endothelial cells adhere to each other. However, because of increased inner pressure of lymphatic vessels loosens the adherence, each endothelial cell of lymphatic vessels breaks off. In this process, because lymph fluid discharges from lymphatic vessels, recovery ability of lymph fluid by lymphatic vessels decrease, leading to exacerbation of edema.
As mentioned above, degeneration of lymphatic vessels is accompanied with proceeding of lymphedema. In other words, unless underlying causes such as obstruction/stagnation of lymph flow are improved, degeneration of lymphatic vessels steadily proceeds. Furthermore, it is known that accumulation of lymph fluid in each part of extremities causes fatty deposits or bloated fatty tissue. Even if conservative therapy or surgical treatment improves lymph flow in an affected extremity, bloated fatty tissue remains. Therefore, early diagnosis/early treatment for lymphedema is important.