Oedema: causes, management and relationship to wounds.

Oedema is a complex condition, and understanding its underlying causes is essential for safe and effective management. The most common aetiology is poor venous return, and venous disease develops when the veins are unable to withstand the hydrostatic pressure within them, leading to a cascade of tissue changes including lipodermatosclerosis, haemosiderin deposition and venous leg ulceration. The most disabling consequence is often secondary lymphoedema. Under normal circumstances, most interstitial fluid that is not reabsorbed at the venous end of the capillaries enters the lymphatic system and is transported back to the heart. When venous valves fail, hydrostatic pressure increases, overwhelming the lymphatic system. Excess fluid is forced into the interstitial space, and the result is oedema.