Lymphedema is caused when protein-rich fluid accumulates in the interstitium due to impaired function of lymphatic tissues. Proteins and other macromolecular wastes with water constitute lymphatic functional loads; these wastes rely upon specially structured absorptive and transport structures in regional anatomy for their return to the central circulation. When lymph stasis prevails, inflammatory processes and fibrosis (lymphostatic fibrosis) trigger changes in tissue density, further entrapping superficial vessels and accelerating the mechanical insufficiency.1
A brief description of primary lymphedema highlights the genetic variability of lymphatic constitution and may explain why seemingly similar patients receiving the same surgical protocol will have different risks for lymphedema over time (Table 104-1). In primary lymphatic diseases and syndromes (eg, Turner syndrome, Noonan syndrome), which include lymphatic dysplasias, these structural malformations involve the mechanisms for uptake, transport, and filtration of lymph. Inherited traits are found in Nonne–Milroy disease, Meige disease, and Distichiasis syndrome.2 The majority of these developmental insufficiencies (87%)1,3 manifest before the age of 35 and cause hypoplasia of vessels and nodes. Syndromes involving hyperplasia, node fibrosis, or aplasia also occur with much less frequency (Fig. 104-1).2 As a result, dysplasia predisposes regions of drainage to inadequate lymph collection, resulting in edema and secondary tissue changes such as chronic inflammation and reactive fibrosis. Since there is no method currently available to image lymphatic vessels safely, it remains a mystery how robust the constitution of lymphatic anatomy is in each patient. Of interest are variations in upper limb drainage that circumvent the axillary nodes to empty at supraclavicular sites. Anatomists theorize that these particular anomalies create advantageous collateral pathways to prevent lymphedema in those fortunate enough to possess these variations.4
Table 104-1 Causes of Primary Lymphedema
Milroy's disease with bandage (pediatric).
The focus of this chapter's discussion is secondary lymphedema, the type caused by a known, significant insult to lymphatic tissues (Table 104-2). It is well documented that lymphedema occurs with great frequency when direct trauma is rendered to regional nodes and/or vessel structures. Degradation of lymphatic health is also noted when adjacent tissues such as superficial and deep veins become diseased, when cellulitis occurs, or when accumulations of adipose or radiation fibrosis mechanically disrupt drainage of skin lymphatics.1,3,5 The following discussion is aimed at assisting with differential diagnosis, since all edemas do not occur in pure form.
Table 104-2 Common Causes of Secondary Lymphedema |Favorite Table|Download (.pdf)
Table 104-2 Common Causes of Secondary Lymphedema
|Chronic Venous Insufficiency|
Lymphedema always involves a compromised mechanical function ...