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Understanding Swelling
Baths, Taps and Drains....
When our body functions normally, fluid moves constantly through our tissues. As blood crosses from our arteries to our veins, it passes through our capillaries.
As this happens fluid moves from our capillaries into the extracellular spaces where it is taken up by our lymphatic system, filtered and returned to the blood stream.
If we think of a bath as our tissues - the bath water is our cells surrounded by a watery solution, the tap is the capillaries constantly delivering nutrients to the cells and the fluid which makes up the water solution (extracellular fluid) and the plughole or drain is our lymphatic system. To remain in balance the drain has to be able to maintain the water level of the bath. If the drain cannot do this then the bath will overflow. This overflow is when we see swelling or 'oedema'.
Lymphoedema is a condition where excessive amounts of fluid accumulates in the tissues resulting in swelling of one or more areas of the body. Lymphoedema is due to a failure of the lymphatic system and occurs either to due damage or disruption to the system itself.
Lymphoedema is different to oedema.
Think of oedema in relation to a tap and lymphoedema as related to the drain. In oedema increased amounts of fluids
Oedema
Oedema or swelling is the accumulation of fluid build-up in the tissues. This can occur for three different reasons:
High output failure:
When the tap flows faster than the drain is able empty the bath. In other words, the fluid load from the capillaries increases above the capacity of the lymphatic system. This can be caused by infection, trauma, early venous insufficiency, deep vein thrombosis or cardiac insufficiency.
Low output failure:
When the drains cannot empty the bath water or in other words the lymphatic system is not working effectively and cannot drain the fluid from our tissues. This can be due to damage, dysfunction or deficiency. Damage could be due to surgery or trauma, dysfunction due to valvular incompetence or loss of contractility, or deficiency due to underdevelopment or absence of areas of the lymphatic system (aplasia or hypoplasia). This is called lymphoedema. Lymphoedema is a high protein oedema.
Combined lymphatic insufficiency:
This is a combination of low and high output failure. For example, if someone has a lymph node dissection due to cancer their lymphatic system will be damaged leading to low output failure. If they then got cellulitis the tissues become more permeable increasing lymphatic load and leading to high output failure.
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