27 - Lymphoedema – Principles, genetics and pathophysiology

Summary

INTRODUCTION

The lymphatic circulation consists of a network of blind-ended capillaries lined with endothelial cells that drain into larger vascular trunks and eventually empty into the blood circulation. It is otherwise totally separate from the blood circulation although lymphatics are often anatomically related to arteries and veins. Lymphatic vessels are found in nearly all tissues and have several important functions including transportation of fluids, plasma macromolecules, and cells back to the blood circulation. The lymphatics also form a major transport route for lipids absorbed from the intestinal tract, and are a critical component of the immune system transporting leucocytes and antigens from the tissues to the lymphoid organs.

Lymphoedema is an accumulation of tissue fluid in the interstitial space as a result of failure of the lymphatic circulation. This can be severe and disfiguring. Defects in the lymphatic system can be primary or acquired. Lymphoedema most frequently affects the legs (80%) although can present as swelling of the arms, face or external genit alia. (Figure 27.1)

CLASSIFICATION OF LYMPHOEDEMA

The diagnosis of lymphoedema should be reserved for those patients in whom a secondary cause of oedematous swelling has been excluded. (Table 27.1). Chronic venous disease is a common cause of unilateral swelling and there are often other characteristic skin changes. Sub-clinical lymphoedema sometimes becomes apparent when other conditions such as venous hypertension cause an increase in fluid and protein forced into the interstitial space that overwhelms a poorly functioning lymphatic system.