Oedema is due primarily to defective lymphatic drainage in the presence of (near) normal net capillary filtration.
Erythematous streaks extend from the site of primary infection on the volar aspect of the forearm to epicondylar nodes at the elbow and thence to enlarged and tender axillary lymph nodes.
Lymphoedema is the end result of insufficient lymphatic outflow due to aplasia, hypoplasia, primary decreased lymphatic contractility (with or without valvular insufficiency) or inflammatory obliteration. Lymphatic hypertension occurs and leads to distension with secondary impairment of contractility and valvular competence. Lymphostasis leads to the accumulation of fluid, proteins, growth factors and other active peptide moieties, glycosaminoglycans and particulate matter, including bacteria. As a consequence, there is increased collagen production by fibroblasts, an accumulation of inflammatory cells (predominantly macrophages and lymphocytes) and activation of keratinocytes. The end result is protein-rich oedema fluid, increased deposition of ground substance, subdermal fibrosis, and dermal thickening and proliferation.
Cross-sectional imaging of the affected limb by means of computerised tomography (CT) or magnetic resonance imaging clearly indicates that lymphoedema, unlike all other causes of oedema, is confined to the epifascial space comprising the skin and subcutaneous tissues. Although muscle compartments may be hypertrophied as a result of the increased work involved in limb movement, they are characteristically free of oedema.
Lymphoedema was originally classified by Allen in 1934 who subdivided it into primary lymphoedema, in which the cause is unknown (or at least unproved), and secondary lymphoedema, in which there is a clear aetiology. Primary lymphoedema is usually further subdivided on thebasis of age of onset and the presence of a family history. Lymphoedema may also be classified on the basis of lymphangiographic findings (see below) and clinical severity regardless of the underlying cause.
The age of onset of painless swelling, together with the presence or absence of a family history or coexistent pathology, will allow differentiation of primary from secondary lymphoedema to be made in most cases. It is important to remember that in developed countries lymphoedema is a relatively uncommon cause of limb swelling.
Unlike other types of oedema, lymphoedema characteristically involves the foot. The contour of the ankle is lost through infilling of the submalleolar depressions, a ‘buffalo hump’ forms on the dorsum of the foot, the toes appear ‘square’ owing to confinement of footwear and the skin on the dorsum of the toes cannot be pinched because of subcutaneous fibrosis (Stemmer’s sign). Lymphoedema usually spreads proximally to knee level and less commonly affects the whole leg. Lymphoedema will pit easily at first but, with time, fibrosis and dermal thickening prevent pitting except following prolonged pressure. Chronic eczema, fungal infection of the skin (dermatophytosis) and nails (onychomycosis), fissuring, verrucae and papillae are frequently seen in advanced conditions. Frank ulceration is rare except in the presence of chronic venous insufficiency, but the two conditions not infrequently coexist and chronic venous insufficiency may actually lead to lymphatic insufficiency. Ulceration can also develop after minor trauma and be slow to heal.Protein-losing diarrhoea, chylous ascites, chylothorax, chyluria and discharge of lymph from skin vesicles (Iymphorrhoea, chylorrhoea) suggest lymphangectasia (megalymphatics) and chylous reflux, but this is rare. Ulceration, nonhealing bruises and raised purple-red nodules should lead to suspicion of malignancy. Lymphangiosarcoma was originally described arising in postmastectomy oedema (Stewart—Treves syndrome) but can arise in any in long-standing lymphoedema. it is rare, aggressive, usually diagnosed late and frequently leads to loss of limb or life.
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