4th June 2025

Aetiology

The lymphatic system is a network of vessels and nodes (glands) that form part of both the vascular system and the immune system. As blood circulates around the body, some of the plasma escapes through the capillaries and into the extracellular space. Any fluid that is not reabsorbed into the capillaries is drained via the lymphatic system. Lymphatic vessels are found throughout the body; they carry the extracellular fluid, protein, and waste products (lymph) back to the blood stream and systemic circulation by ultimately draining into the left and right subclavian veins. Along the way, lymph passes through lymph nodes, where microorganisms are presented to immune cells.

Lymphoedema becomes apparent once ≥80% of lymphatic drainage to a body part is impaired (lymphostasis). Accumulation of lymph in the tissues leads to fat hypertrophy, the subcutaneous tissues become thickened and the normal functioning of the immune system is impaired. Over time this leads to further tissue inflammation and fibrosis.

https://upload.wikimedia.org/wikipedia/commons/thumb/2/21/Upper_limb_lymphedema.jpg/640px-Upper_limb_lymphedema.jpg

Primary lymphoedema:

• Congenital abnormalities of the lymphatic system lead to reduced function; drainage of lymph is compromised as a result.
• Can be sporadic (most common), familial or as part of a syndrome (e.g. Milroy’s disease, Noonan syndrome and Turner syndrome).
• Most commonly affects the lower limbs.

Secondary lymphoedema:

• Occurs after damage to a previously functioning lymphatic system.
• Causes include: infection, trauma, malignancy and its treatment (radiotherapy and surgery).
• Lymphoedema will become apparent 1-2 years after the initial damage to the lymphatic system.
  • E.g. breast cancer: patients frequently undergo axillary lymph node biopsy, dissection or radiotherapy (leading to scarring and fibrosis).
  • E.g. lymphatic filariasis: caused by one of three species of parasitic nematodes (roundworms): Wuchereria bancrofti, Brugia malayi or Brugia timori; only Wuchereria bancrofti is found in the Americas.
• Lymphatic drainage is impaired by either direct obstruction (from roundworms) or local tissue inflammation.