The Lymphatic System

Function of the Lymphatic System

The lymphatic system’s primary function is to absorb and transport lymph fluid throughout the body. The lymphatic system functions in parallel to the circulatory system, but it is made up of its own circuit of lymph vessels, nodes, and lymphoid tissues. Lymph fluid is made of proteins, water, impurities, and waste products from the body’s tissues. In addition, the system produces and transports immune cells (lymphocytes) that fight bacteria and viruses.

Lymph fluid is normally absorbed from body tissues and moves through a series of vessels and lymph nodes. As the fluid passes through the nodes, it is purified of harmful bacteria and viruses. The lymphatic system has regional networks of vessels that are responsible for handling fluid from specific body tissues.

The Superficial Lymphatic System

The superficial lymphatic system is made up of vessels and nodes that are located just under the superficial skin. Key areas include
axillary lymph nodes (which are located in the armpits and filter fluid from the chest, breast, arm, and back) and inguinal lymph nodes (which are located in the bend of the hip and filter fluid from the leg, lower abdomen, buttock, and genital region).

The Deep Lymphatic System

The deep lymphatic system is made up of larger vessels that are more centrally located and found in the deeper tissues in the body. Key areas include supraclavicular and deep cervical lymph nodes (which are located above the collar bone and along the sides of the neck and filter fluid from the head and neck region) and deep abdominal/pelvic lymph nodes (which are located in the abdomen and surround the organs and intestines in the deeper body cavity). This system of lymph nodes is important to the transport of fluid from all of the lower parts of the body. Lymphoid tissue is found in other areas of the body as well, including the tonsils, spleen, intestinal wall, and bone marrow.

What is Lymphedema?

Lymphedema is an abnormal collection of lymphatic fluid in the tissues just beneath the skin. This swelling commonly occurs in the arm or leg, but it may also occur in other body areas including the breast, chest, head and neck, and genitals. Lymphedema develops when a body region, where lymphatic vessels and lymph nodes are missing or impaired, becomes overloaded with lymphatic fluid.

Lymphatic fluid is normally transported in our body by an extensive network of vessels and nodes. When these vessels are damaged or malformed, there is a risk that lymphatic fluid will not be adequately transported and may result in fluid backing up in body tissues. When fluid congests in the tissue, swelling occurs. This swelling is called lymphedema.

If the condition is left untreated, it leads to progressive tissue swelling over time. Lymphatic fluid congestion also reduces healthy blood flow to the tissue, interferes with wound healing, and enables bacteria to grow, which increases the risk of tissue infections.

Lymphedema should not be confused with other types of edema resulting from venous insufficiency, cardiac conditions, kidney failure, or other inflammatory processes. These swelling conditions are systemic, while lymphedema occurs only in the specific regions of the body.

There are two types of lymphedema: primary and secondary.

Primary Lymphedema

In some cases, lymphedema can occur from hereditary or genetic abnormalities that cause malformation of the lymphatic system. This is called primary lymphedema. Primary lymphedema can impact any part of the body and may involve swelling in multiple limbs or body regions.

Primary lymphedema can be present at birth from genetic causes such as Milroy’s disease. It may also be associated with arterial-venous abnormalities (AV malformations) such as hemangioma, lymphangioma, Klippel Ternary, and Park-Weber Syndrome.

The most common form of primary lymphedema is lymphedema praecox, which appears during puberty, mostly in girls, and usually affects a lower extremity. A second form of primary lymphedema is lymphedema tarda, which begins later in life, typically after age 35, and can occur in both male and female adults.

Primary lymphedema is rare as a cause of lymphedema. Because of the linkages between primary lymphedema and genetic conditions, individuals diagnosed with primary lymphedema should seek genetic counseling to determine whether additional testing is needed.

Secondary Lymphedema

Secondary lymphedema occurs because of damage or trauma to the lymphatic system. Common causes of lymphatic system damage include: cancer-related surgery, radiation therapy, traumatic injury, or parasitic infection.

Specific cancer-related surgeries, such as those done for tumor removal, require removal of lymph nodes. The removal of lymph nodes reduces the system’s ability to move fluid and puts people at risk of developing swelling. Surgical techniques such as sentinel node biopsy strive to remove fewer nodes, aiming to preserve the lymphatics and reduce risk for swelling. The sentinel node procedure still disrupts the lymphatic system and introduces some risk for developing lymphedema.

Radiation therapy is a standard treatment for many types of cancer. Radiation can damage otherwise healthy lymph nodes and vessels, causing scarring that interrupts the normal flow of the lymphatic fluid and introduces the risk for swelling.

Once the lymphatic system is damaged, secondary lymphedema can develop any time there is undue trauma or injury to the body. Because the lymphatic system is impaired, its ability to absorb and carry fluid is diminished. Therefore, if the system is overloaded with fluid from an injury or infection that causes inflammation, swelling may result.

Traumatic injuries inadvertently or accidentally disrupt lymphatic vessels and may result in lymphatic system impairment and lead to the onset of lymphedema.

Parasitic infections are world-wide the most prevalent cause of damage to the lymphatic system and lead to a form of lymphedema called filariasis. This condition affects people primarily in subtropical areas of Southeast Asia, India, Central America, and Africa. A mosquito bite injects the filarial larvae into the lymphatic system. These larvae mature into adult worms in the lymphatic vessels, causing severe lymphedema.

Signs and Symptoms of Lymphedema

Lymphedema can develop in any part of the body or limb(s) where lymph nodes or vessels have been removed or damaged. Signs or symptoms of lymphedema include sensations of fullness or heaviness in the limb(s), tightness of the skin, visible swelling, difficulty fitting into clothing or shoes, or changes in the fit of jewelry. Any noticeable symptoms and signs of swelling in the limb or body region, warrant medical attention even if the swelling seems to go away completely.

Lymphedema develops in a progressive manner, from mild to severe, making early identification of the condition important. The stages of lymphedema are:

Stage 0 (Latency)

Lymphedema begins to develop deep within the tissues and can progress very slowly. Early changes happen without obvious, noticeable swelling, however, the fluid congestion causes sensations such as tightness, heaviness, or diffuse tingling in the at-risk limb. Despite the normal appearance of the limb, there may be sub-clinical changes occurring that can be measured and identified. Responding to changes in this early stage can help to prevent the onset of the condition. Special imaging or other lymphatic technology is required for diagnosis in this stage.

Stage 1 (Spontaneously Reversible)

In this early stage, swelling may or may not be present all the time. Swelling many come and go intermittently. When swelling is present, the skin will ‘pit’, meaning that the area indents with pressure and holds the indentation. Elevation of the swollen limb provides relief and reduction in the swelling. It is important to seek out treatment for lymphedema management at this early stage to help to prevent the condition from becoming progressively more swollen.

Stage 2 (Spontaneously Irreversible)

In this stage, the tissue now has obvious signs of stagnant swelling that do not go away with elevation. The tissue will be firmer and show signs of less pitting. The tissue consistency change is caused by the formation of fibrosis. Fibrosis is the scarring of the tissue due to the prolonged presence of stagnant lymph. This marks the beginning of the hardening of the limb and progressively more aggressive swelling. Seeking treatment at this stage will help to reduce limb volume and improve tissue. The treatment will be more intensive and will require more vigilant follow-up to maintain the swelling.

Stage 3 (Lymphostatic Elephantiasis)

At this stage, the tissue becomes very hard (fibrotic) and may begin to develop thickening on the surface of the skin. Excess skin forms on the limb and there is greater potential for open, seeping areas. Due to the high concentration of lymph fluid, the swollen limb(s) becomes an ideal culture medium for bacteria to thrive and recurrent infections may be common. Moreover, untreated lymphedema can lead to a decrease or loss of functioning of the limb(s), skin breakdown, chronic infections, and, sometimes, irreversible complications. Treatment is still beneficial at this stage and can have a remarkable impact on tissue softening and decongestion of the swelling.

These stages represent the natural progression of lymphedema when the condition is left untreated. At any stage, lymphedema can be treated and the progression halted and, in some instances, reversed. The importance of early identification and early management should be stressed.