Lymphoedema of the lower extremities--background, pathophysiology and diagnostic considerations

Lymphoedema of the lower extremities is a chronic debilitating disease that is often underdiagnosed. Early diagnosis and treatment is paramount in reducing the risk of progression and complications. Lymphoedema has traditionally been defined as interstitial oedema and protein accumulation because of a defect in the lymphatic drainage; however, some findings suggest that the interstitial protein concentration may be low in some types of lymphoedema. Primary lymphoedema is caused by an inherent defect in the lymphatic vessels or lymph nodes. Secondary lymphoedema is caused by damages to the lymphatic system most often caused by cancer or its treatment. Many of the underlying pathophysiological mechanisms have yet to be elucidated. Many methods have been developed for examination of the lymphatic system. Lymphoscintigraphy is presently the preferred diagnostic modality. Lack of consensus regarding protocol and qualitative interpretation criteria results in a too observer dependent outcome. Methods for objectifying the scintigraphy through quantification have been criticized. Depot clearance rates are an alternative method of quantification of lymphatic drainage capacity. This method however has mostly been applied on upper extremity lymphoedema. The aim of this review is to provide a literature-based overview of the aetiology and pathophysiology of lower extremity lymphoedema and to summarize the current knowledge about lymphoscintigraphy and depot clearance techniques. The abundance of factors influencing the outcome of the examination stresses the need for consensus regarding examination protocols and interpretation. Further studies are needed to improve diagnostic performance and understanding of pathophysiological mechanisms.