Oedema
From Pharmpedia
Oedema is an abnormal clinical state characterised by accumulation of interstitial or tissue fluid. Cutaneous oedemas can be diagnosed by the simple test: pitting on pressure. Theoretically, oedemas are caused by three different mechanisms:
- A hydrostatic pressure gradient, which is too great (so-called high pressure oedema or cardiac oedema at heart failure with increased venous and central venous pressure),
- A colloid-osmotic pressure gradient, which is too low and caused by too low concentrations of plasma proteins (so-called hunger oedema and renal oedema), and
- Leakage in the capillary endothelium (so-called permeability oedema with too much protein in the oedema fluid). Burns cause increased capillary permeability for proteins, by infections or by allergy.
Cardiac oedema develops in the dependent parts of the human body, where the hydrostatic gradient is greatest (see congestive
heart failure, Fig. 10-10).
Renal oedema is frequently found in loose tissues, such as the subcutaneous tissue around the eyes (see Chapter 25).
Lymphatic oedema is special form of oedema that can be congenital or acquired. A child born with insufficient development of the
lymphatic system will suffer from gradual swelling of the affected body part as a result of accumulation of interstitial fluid.
Surgical destruction of lymphatic vessels can result in acquired, lymphatic oedema (eg, following mastectomy).
Inflammative processes, cancer cells or filarias (elephantiasis) also can obstruct lymphatic vessels, so the limbs swell and
become oedematous “elephant limbs.”
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