Chapter 22: Lymphedema

GENERAL CONSIDERATIONS AND HISTORY

Lymphedema, characterized by hydrostatic interstitial edema and soft tissue hypertrophy within the affected limb (Figure 22-1), is the disease that develops with end-organ failure of the lymphatic vasculature.

Tissue fluid homeostasis requires the continuous presence of sufficient lymph egress from the limb. When lymph transport capacity is insufficient, interstitial fluid accumulation and regional edema supervene. The presence of lymphedema may reflect either the presence of intrinsic functional defects in lymphatic vascular structure or function, or the advent of lymphatic failure within previously normal vessels as a consequence of sustained circulatory overload. The latter category is predominated by conditions that increase capillary filtration, including right atrial hypertension and chronic venous disease. Intrinsic lymphatic defects can be either primary, on the basis of intrinsic defects, or secondary, caused by disruption of the lymphatic vasculature by surgery, radiation, trauma, or infection. The lymphedema that results from either of these two categories is relatively indistinguishable.

Lymphatic Anatomy and Physiology

The lymphatic vasculature was first anatomically identified by Gasparo Aselli in the seventeenth century.¹ Appreciation of the more detailed anatomy of this vasculature has grown over the ensuing centuries, through the meticulous work of Pecquet, Bartholinus, Rudbeck, Sappey, von Recklinghausen, and others.¹

The modern conception of lymphatic anatomy includes a description of the lymphatic capillary as a blind-ended tubular structure comprised of lymphatic endothelial cells. In contrast to the blood vascular capillaries, these structures lack an intact basement membrane, which facilitates the entry of proteins and particulate material that are excluded from blood vascular entry. As the capillaries coalesce into larger, 100- to 200-mm vessels, they acquire a smooth muscle media and an adventitia. The lymphatic collectors also have intraluminal valves to ensure unidirectional, central flow.^2,3 In the legs, lymphatic collectors are organized into superficial and deep components. The superficial aspect has medial and lateral channels. The medial channel originates on the dorsum of the foot and follows the course of the saphenous vein. The lateral channel originates on the lateral aspect of the foot and travels to the midleg where, after crossing anteriorly, it follows the course of the medial lymphatics toward the inguinal nodes. The deep lymphatics arise in the subcutaneous compartment and follow the deep blood vasculature as they course toward the inguinal nodes. The deep lymphatics typically communicate with the superficial system only through the popliteal and inguinal lymph nodes. The lymphatic conduits from the lower extremities ultimately gain access to the thoracic duct, the largest of the central lymphatic channels. The thoracic duct transmits the lymph flow from the lower extremities to the central vasculature through its anastomosis with the left ...