CHAPTER 69

Lymphatic Disorders

Like the venous system, the lymphatic system transports fluids throughout the body. The lymphatic system consists of thin-walled lymphatic vessels, lymph nodes, and two collecting ducts (see art on page 1098). Lymphatic vessels, located throughout the body, are larger than capillaries, and most are smaller than the smallest veins. Most of the lymphatic vessels have valves like those in veins to keep the lymph, which can clot, flowing in the one direction (toward the heart). Lymphatic vessels drain fluids from tissues throughout the body that have diffused through the very thin walls of capillaries. The fluids contain proteins, minerals, nutrients, and other substances, which provide nourishment to tissues. However, most of the fluid is reabsorbed into the capillaries. The rest of the fluid (lymph) is drained from the spaces surrounding the cells into the lymphatic vessels, which eventually return it to the veins. Lymphatic vessels also collect and transport damaged cells, cancer cells, and foreign particles (such as bacteria and viruses) that may have entered the tissue fluids.

All lymph passes through strategically placed lymph nodes, which filter damaged cells, cancer cells, and foreign particles out of the lymph. Lymph nodes also produce specialized blood cells designed to engulf and destroy damaged cells, cancer cells, infectious organisms, and foreign particles. Thus, important functions of the lymphatic system are to remove damaged cells from the body and to provide protection against the spread of infection and cancer.

The lymph vessels drain into collecting ducts, which empty their contents into the two subclavian veins, located under the collarbones. These veins join to form the superior vena cava, the large vein that drains blood from the upper body into the heart.

The lymphatic system may not perform its function adequately when the quantity of fluid is excessive or when the lymph vessels or nodes are damaged or removed during surgery, become blocked by a tumor, or become inflamed.

Lymphedema

Lymphedema is the accumulation of lymph resulting in swelling.

Lymph fluid does not drain from tissues, causing swelling.

Compression bandages or pneumatic stockings can reduce the swelling.

Lymphedema results when the lymphatic system cannot adequately drain lymph from the tissues, causing swelling. Lymphedema may be due to conditions present at birth (congenital) or to conditions that develop later (acquired).

Congenital Lymphedema: This disorder results from having so few lymphatic vessels that they cannot handle all the lymph. The problem almost always affects the legs; rarely, it affects the arms. Women are much more likely than men to have congenital lymphedema.

Rarely, the swelling is obvious at birth, but usually, the lymphatic vessels can handle the small amount of lymph produced in an infant. More often, the swelling appears later in life, as the volume of lymph increases and overwhelms the small number of lymph vessels. The swelling starts gradually in one or both legs. The first sign of lymphedema may be puffiness of the foot, making the shoe feel tight at the end of the day. The shoe may leave indentations in the skin of the foot. (Many people who do not have lymphedema experience swelling after they stand for prolonged periods. They may have indentations around their ankles after they wear ankle socks, but the indentations are much less deep than those of lymphedema, and the surrounding area is not puffy.)

In the early stages of congenital lymphedema, the swelling goes away when the leg is elevated. This disorder worsens with time: The swelling becomes more obvious and does not disappear completely, even after a night’s rest.

Acquired Lymphedema: Acquired lymphedema is more common than congenital lymphedema. It typically appears after major surgical treatment, especially after cancer treatment in which lymph nodes and lymphatic vessels are removed or treated with radiation. For example, the arm tends to swell after removal of a cancerous breast and lymph nodes in the armpit. Scarring of lymphatic vessels from repeated infection also may cause lymphedema, but this type of scarring is very uncommon except among people who have an infection due to the tropical parasite Filaria (filariasis).

In acquired lymphedema, the skin looks healthy but is puffy or swollen. Pressing the area with a finger does not leave a significant indentation, as it does when edema results from inadequate blood flow in the veins. Rarely, especially in filariasis, the swollen limb becomes extremely large and the skin is so thick and ridged that it looks almost like elephant skin. This disorder is called elephantiasis.

Treatment

Lymphedema has no cure. For people with mild lymphedema, compression bandages can reduce the swelling. People who are more severely affected may wear pneumatic stockings (see page 435) every day for an hour or two to reduce the swelling. Once the swelling has been reduced, the person must wear elastic stockings up to the knee every day from the moment of rising until bedtime. This measure controls the swelling to some degree. For lymphedema in the arm, pneumatic sleeves—like pneumatic stockings—can be used every day to reduce the swelling; elastic sleeves are also available. For elephantiasis, an extensive operation may be performed to remove most of the swollen tissues under the skin.