What Causes Lymphedema
What is Lymphoedema?
Lymphoedema is a chronic condition characterised by an abnormal collection of fluid (lymph), resulting in swelling of a limb/extremity. It is however, important to note that lymphoedema differs from oedema. Lymphoedema is high-protein oedema, resulting from failure of the lymphatic system, whereas oedema comprises of simply water. It is well-recognised that damage to the lymphatic system impairs the healing of both venous and non-venous chronic wounds(1).
The term lymphoedema was introduced in the early 20th century, when systems of manual lymphatic drainage (MLD) and comprehensive decongestive physiotherapy (CDP) entered common practice for lymph drainage. Before that time, for centuries, the term elephantiasis was used to describe the swelling that occurred due to lymphatic failure/valvular incompetence.
Lymphoedema has a multitude of causes. It can be inherited (primary) or may occur due to trauma (secondary). The most common cause in India is Filariasis. Filariasis is a parasitic disorder caused by worms residing in the lymphatic system. Other causes can include trauma, cancer, injury, venous diseases etc. These are showing a rising incidence which has changed the perspective of lymphedema from a poor man’s disease to one that affects all classes. The most common cause of secondary lymphedema, in developed countries, is cancer, especially after surgery. A study of the London population by Moffatt et al(1), reported a prevalence rate of 1.33/1000 of lymphoedema, rising to 5.4/1000 in the over 65-year age group. Lymphoedema secondary to malignancy has resulted in 60,000 new cases per annum in Shanghai alone(1). In Germany the estimates are around 120,000, including 40,000 with primary lymphedema and 80,000 with secondary lymphedema.
Pathophysiology
Lymphoedema is now recognised as a state of chronic and continuing infection as well as inflammation. It results when lymphatic vessels are either damaged or impaired. When the impairment becomes so great that the lymphatic fluid exceeds the lymphatic transport capacity, an abnormal amount of protein-rich fluid collects in the tissues of the affected area. If left untreated, the stagnant lymph increases in amount and could affect oxygen availability, and interfere with wound healing. More importantly, it provides a culture medium for bacteria, making infection (lymphangitis) a very common complication of accumulated lymphatic fluid. Any anti-inflammatory action has to start from the groin or axillary nodes which are either absent, damaged or in any case, far removed from the site of infection. Such attacks of infection thus worsen the disease condition by causing blockage of existing lymph channels and slowing up the process of lymph regeneration. Infection also induces fibrosis as well as increases the fluid content of the limb. Thus, an untreated patient with a swollen limb gets sucked into a vicious cycle of accumulated fluid – causing infection and further blockage causing even more oedema. Finally we have a patient with large fibrotic elephant hide type limbs – called Elephantiasis.
Lymphedema is most commonly caused by the removal of or damage to your lymph nodes as a part of cancer treatment. It results from a blockage in your lymphatic system, which is part of your immune system. The blockage prevents lymph fluid from draining well, and the fluid buildup leads to swelling.
There are two types of lymphedema - primary lymphedema and secondary lymphedema. Both types relate to lymph vessels or lymph nodes that are missing, damaged, removed or otherwise impaired.
Primary Lymphedema
The lymphatic system may be abnormal from birth. When a lymphatic system is no longer able to cope with the demands placed on it, primary lymphedema can develop. It is called 'primary' as the cause of the impairment is to be found in the structure of the lymphatic system itself. Primary lymphedema can be classified to age of onset.
| Congenital | The lymphedema is noticeable at birth | |
| Praecox | Lymphedema occurs after birth, but before age 35 | |
| Tardum | Lymphedema presents after age 35 | |
Primary lymphedema can present as a variety of abnormalities:
| Aplasia | Portions of the lymph systems are missing. | |
| Hypoplasia | Lymph collectors are smaller in size, or the number of collectors is below normal levels. This is the most common abnormality seen in primary lymphedema. | |
| Hyperplasia | Lymph collectors are larger than normal, but don't always function as well as normal lymphatics. | |
Secondary Lymphedema
Secondary lymphedema is caused when an outside factor directly impacts the lymph system. The lymphatic system is fully adequate and functions perfectly until it is damaged. Causes of secondary lymphedema include:
| Cancer surgery/radiation | Removal of lymph nodes that is often associated with cancer can disrupt lymph flow. Radiation treatment can also impair lymph flow. | |
| Malignant tumors | The tumors put pressure on lymph vessels, decreasing fluid flow. | |
| Trauma | The body sustains an injury, including burns or a crushing injury, which can inhibit the flow of lymph fluid. | |
| Infection | Recurrent infections can cause failure of lymphatic vessels. | |
| Chronic Venous Insufficiency | This venous disorder puts extra pressure on your lymphatic system, leading to a breakdown. | |
| Obesity | The increased lymphatic flow, and often time-increased pressure on lymph nodes, can impair lymphatic flow. | |
| Self-Induced | A patient uses a tourniquet to impair lymphatic and venous flow. | |
| Iatrogenic | This is lymphedema caused by a health care related procedure, such as an interventional procedure or tourniquet. | |
| Filariasis | A parasitic disease found mostly in third-world countries that impairs the lymphatic system. | |
| Trauma and Tissue Damage | Infection | Venous Disease |
| Lymph node excision (Breast, Uterus, Penis, Testes, Skin etc) Radiotherapy Burns Varicose vein surgery/harvesting Large/ circumferential wounds Scarring | Cellulitis/erysipelas Lymphadenitis Filiariasis Tuberculosis(rare) | Post-thrombotic syndrome (DVT) Intravenous drug use Chronic venous insufficiency |
| Malignant Disease | Inflammation | Immobility and Dependency |
| Lymph node metastases Infiltrative carcinoma Lymphoma Pressure from large tumours | Rheumatoid arthritis Psoriatic arthritis Dermatitis/eczema Sarcoidosis and oro-facial granulomatosis Podoconosis (crystalline blockage of limb lymphatics) | Dependency oedema Obesity Paralysis Sleep apnea |
Other types of oedema
Lipedema
Often confused with lymphedema, lipedema is an adipose tissue disorder or abnormal accumulation of fatty tissue. It affects mostly women, often developing around the time of a hormonal change (i.e. puberty, pregnancy or menopause). The condition leads to tissue enlargement most commonly around the legs, hips and/or buttocks. Unlike lymphoedema, the enlargement usually stops at the ankles and the feet are spared. However, it tends to be in both legs. It mostly affects the lower limb but can develop in the arm (the hands are usually spared). It often leads to a sensation of the limbs being ‘heavy and tight’ and the skin may be tender to touch, cooler than unaffected areas, sensitive and/or bruise easily. Despite dieting or increasing physical activity, the volume of the limbs does not decrease and there is a distinct disproportion between the limbs and the trunk. Those who have had lipedema for many years often develop a lymphatic component, as the fatty tissues tend to obstruct lymphatic drainage. This is known as lipo-lymphoedema. The surface of the skin is more uneven, there may be ridges of fat under the skin, the limb is more distorted and mobility may be impacted. The foot can become swollen.
Lymphovenous edema
This condition results in both the venous lymphatic systems not functioning adequately due to an underlying venous problem/disease and results in a swelling. When valves weaken or there are abnormalities in the venous walls, blood can flow backward and increase the pressure in the veins, known as venous hypertension. If venous hypertension is sustained over time, the vein walls stretch and the valves no longer close. This further increases hypertension which can lead to a pooling of blood, discomfort and varicose veins. The common signs are staining of the skin, spider veins and varicose veins. A swelling occurs when the increase in lymphatic flow to the area is much greater than the lymph transport capacity.