Lymphedema is a chronic, debilitating, and distressing condition affecting an estimated 35 million individuals in the United States and over 140,200 million people worldwide (O’Donnell et al., 2020). Lymphedema is “the abnormal accumulation of interstitial fluid and fibroadipose tissues resulting from injury, infection, or congenital abnormalities of the lymphatic system” (Mahera, 2023).
In the past, Starling’s Law, introduced by Earnest Henry Starling (1866-1927), described a reabsorption process in the microcirculation where it was believed that most (90%) of the fluid leaking into the interstitial spaces of the lower extremities from venous insufficiency, would enter into the venous end of the capillaries (such as when compression was applied) and end up back in the blood circulation, while 10% of this interstitial fluid would be returned to the blood circulation via the lymphatic system. However, newer evidence suggests that 0% of interstitial fluid is reabsorbed back into the venous end of the capillaries, and 100% of the interstitial fluid load is managed by the lymphatic system (Hettrick & Ehmann, 2019). Bjork (2018) reported, “It has been established that the endothelial glycocalyx layer (EGL) controls the movement of proteins and fluid across the blood capillary wall. Despite prevailing principles regarding Starling’s Law, it is now understood that there is no reabsorption of fluid back into the venous side of blood capillaries. Rather, there is only diminishing net filtration across the capillary bed, and fluid and blood proteins are removed from tissues via reabsorption through lymphatic capillaries alone. Consequently, a new paradigm emerged indicating that all edemas are on a lymphedema continuum.” The revision of Starling’s Principle with a clearer understanding of the endothelial glycocalyx layer (EGL) resulted in a new model of microcirculation based on evidence reported by Levit and Michel in 2010. (Hettrick & Aviles, 2022).
The new evidence demonstrated that the lymphatics manage 100% of interstitial fluid edema and has led to the term “phlebolymphedema,” which has been defined as edema “due to insufficiency of the venous or/and lymphatic system, in combination with possible systemic contributors, leading to accumulation of interstitial protein-rich fluid in the interstitial space” (Ostler, 2018).
Regardless of where it originates, when interstitial body fluids (containing foreign debris, proteins, white blood cells, and microorganisms) leave the interstitial spaces and enter the lymphatic system, it is called lymphatic (or lymph) fluid. This course will focus on the management of lymphedema in general. Still, it is important to recognize that managing all edema (such as what is classified as venous insufficiency) will benefit from considering evidence-based treatment methodologies aimed at improving lymphatic drainage since “all edema is on a lymphedema continuum” (Hettrick & Aviles, 2022).
It is also important to note that this course is not meant to be a “how to” course on performing lymphedema therapy. Nor is the goal of this educational program to make the reader a lymphedema specialist or therapist, but rather to provide the reader with an overview of the problem of lymphedema and become familiar with diagnostic, differential, and treatment options.
The lymphatic circulatory system has been thought to be similar to the cardiovascular circulatory system, with lymph vessels and channels and two types of capillaries. However, it does not have the benefit of cardiac muscle contractions to pump lymph fluid along, and there is not a continuous string of vessels that connect directly. Therefore, it is described as a relatively passive system of fluid movement. In general, contracting and relaxing muscles in the area of the lymphatic vessel help move the fluid through the system. In cases where the lymphatic system is overloaded, the lymphatic system is damaged, or both, it needs the assistance of manual massage, mechanical pumps, compression sleeves, stiff compression wraps, and bandaging systems to assist with lymphatic absorption, capillary filtration, shifting fluid into non-compressed regions and to improve lymph management. In addition, it is now known that “the integumentary and lymphatic systems are interdependent.” Hettrick & Aviles (2022) report, “When initial lymph fills the interstitial space, elastic fibers are stretched, thereby expanding the lumen of the lymphatic capillary and opening the overlapping flaps to allow lymph to enter the capillary plexus. Thus, lymphatics must act as a mechanical extension of the interstitium to function (Bjork, 2018; Hettrick & Aviles, 2022).
Lymph vessels are typically larger than capillaries but smaller than veins. Most of the larger lymph vessels have one-way valves to keep the flow of lymph fluid uni-directional – toward the heart and preventing back-flow or clotting. The lymph system also has hundreds of lymph nodes that serve as filters for the lymphatic fluid (Lawenda et al., 2009). There are two separate systems of lymph drainage within the body: those found within the subcutaneous tissues, which drain lymph fluid that has diffused through capillaries from the superficial tissues and skin of the body, and those that drain lymph fluid diffused from tissues within the deeper spaces and structures of the body such as the head, neck, and thorax. The fluid movement through the lymphatic drainage system occurs partly by muscles contracting and increasing pressure against other structures, effectively “squeezing” the fluid from one place to another.
The deeper lymphatics drain the deep tissues, such as muscle, and follow a pathway similar to the cardiovascular blood vessels. Superficial lymphatics are in the subcutaneous fatty layer of the body and drain the subcutaneous tissues and skin. The deeper lymphatic system connects with the more superficial lymphatic system through perforating vessels, which pass through the fascia (fibrous layer covering muscle)( NLN, n.d.). However, these vessels do not connect directly and have open spaces between them. The lymph fluid (containing proteins, cellular debris, and fluids that have escaped from cells, tissues, and semi-permeable blood vessels) passes from the intercellular spaces of tissues into the lymphatic vessels, where they are directed to lymph nodes – the filters of the body. The lymph vessels return the filtered lymph fluid to the venous system. The smallest lymph vessels, which are blind at one end and collect lymph fluid in tissues and organs, are also known as lymph capillaries. However, they are different from those found in the venous-arterial circulatory system.
|Adult humans typically have about 800 lymph nodes throughout their body: Extremities, head & neck, axilla, thorax, abdomen, and groin. Lymph nodes are typically smaller than 1-2 cm in size. The lymph node is composed of 4 parts from inner to outer structure: Medulla (center most), Cortex, Subscapular Sinus, and Capsule (outer most). (Bujoreanu et al, 2023). Lymphedema may occur in any part of the body, and is not limited to the extremities (Bryant & Nix, 2023).|
For more than 100 years, it was thought that the lymphatic channels did not cross the midline of the body, yet research initiated back in the 1950s after the development of lymphoscintigraphy and confirmed by Fife et al. (2014) suggests this is not the case. Fife et al. demonstrated with fluoroscopy and radio-opaque tracers that Lymphatic fluid was seen to cross the body's midline (head, neck, chest, and trunk) during lymph massage. This information is important when identifying sentinel lymph nodes to dissect in cancer cases and for manual lymphatic massage techniques (Uren et al., 2003).