Lymphoedema Pathology and Clinical Features

Lymphoedema is chronic progressive swelling in a region due to excessive build-up of protein-rich interstitial fluid. It develops when the lymphatic load is consistently greater than the lymphatic transport capacity in a specific lymphatic territory.
•Low-output lymphoedema occurs when the lymphatic system’s ability to transport is reduced. This may be primary due to congenital lymphatic dysplasia or secondary due to lymphatic damage or obliteration through surgery, irradiation or chronic inflammation.
• High-output lymphoedema can develop when there is an increased load on an otherwise normal system. This may be caused by lower limb varicose disease with peripheral oedema or phlebo-lymphoedema, or general medical
conditions such as hepatic cirrhosis causing ascites or nephrotic syndrome causing anasarca. Transport capacity through intact lymphatics is overwhelmed by an excessive burden of capillary filtrate. Lymphatic transport is normal in the early stages but long-standing high-output lymphatic failure causes gradual secondary functional deterioration of draining lymphatics. This reduces
their transport capacity even if the underlying disease is corrected, and the lymphatic system eventually fails.