The lymphatic system collects excess tissue fluid and large particles, particularly proteins and protein debris, and returns them to the blood stream. The extensive lymphatic plexuses that cover the surface of the body, and all organs except the brain, are not usually visible unless they become inflamed (lymphangitis). The lymph nodes, placed along the lymphatic collecting pathways are palpable, and become enlarged in certain diseases. The final common pathways back to the venous system are through the thoracic duct and the right lymphatic duct, respectively passing to the left and right subclavian veins.
Maldevelopment of lymphatics (aplasia, hypoplasia and hyperplasia) may lead to an accumulation of tissue fluid (primary lymphedema – figure 111), and this may also occur with occlusion of the lymphatic vessels and nodes, as with chronic inflammatory and metastatic disease, radiotherapy, and after surgical removal (secondary lymphedema). The causes of a swollen leg are considered in table 3.
Table 3 Swollen leg
Lymph node enlargement (lymphadenopathy) may be primary, due to lymphoid disease (Hodgkin’s and non-Hodkin’s lymphoma) or secondary. The latter is usually due to inflammatory or metastatic disease (table 4). Lymph node enlargement secondary to acute inflammation is very common, e.g. lymph nodes are the commonest lump in the neck (figure 112). Lymphadenopathy often occurs at specific sites and this can be a useful diagnostic feature, e.g. the jugulodigastric node is commonly involved with disease of the anterior two-thirds of the tongue, and all lymph from the tongue drains via the jugulo-omohyoid node.
Table 4 Lymphadenopathy
When examining the lymphatic system, start with the head and neck, proceed to examine the axillae and, if enlarged nodes are located, examine for inguinal, epitrochlear and popliteal node enlargement, and for hepatosplenomegaly. In practice, in the absence of demonstrable or suspected lymphadenopathy, examine the axillae with the breasts in the female and with the thorax in the male. The inguinal nodes are then palpated when you examine the inguinal, scrotal and perineal regions.