 Goodman CH. 13

 Lymphatic system :  1. helps maintain fluid balance in the tissues  2. fights infection  3. assists with the removal of waste products from the extracellular spaces  **This drainage system is separate from the general circulatory system but the conduit for returning tissue fluids is the circulatory system.

 **How does this actually take place…?  **Glad you asked!  **The interstitial fluid that remains after the extracellular fluid is resorbed via the veins is taken up by the initial lymphatic vessels>into larger collecting vessels>into lymphatic trunks>and back to the right side of the heart via the lymphatic ducts that empty into the subclavian veins in the neck.

 **While it is really not a nice thing to do, we can think of the lymphatic system as a sanitation system of a major city. **It is largely ignored until it is disrupted and backs up….and the “garbage” piles up>>>> lymphedema **Of the fluid volume that perfuses the tissues, 90% reenters the circulation via the venous capillary network; the other 10% reenters via the lymphatic system (this can amount to 2L/day!)

 The lymphatic system is a pressure-driven system based on the principles of osmotic diuresis  The lymphatic system works based on a balance of hydrostatic and oncotic pressure (like flow across a capillary membrane)  If normal lymphatic transport mechanisms are disrupted (example: by scar tissue or reduced muscle pumping), significant accumulations of water and protein can remain in the tissue spaces.  This results in latent, acute, or chronic lymphedema.

 1. Superficial vessels> rely on oncotic and hydrostatic pressures, muscle contraction, arterial pulsation, and gentle movement of the skin to move lymph fluid  2. Deep vessels> generally parallel the venous system. They have smooth muscle and valves to help prevent backflow.  3. Nodes> serve an immune function. The nodes serve as filters to cleanse the lymph of waste products and cellular debris.  *Vessels entering the lymph nodes are afferent. Those leaving are efferent.

 *There are 4 pressures:  1. plasma hydrostatic pressure  2. tissue hydrostatic pressure  3. plasma colloid osmotic pressure  4. tissue colloidal osmotic pressure  *All of these determine how much fluid moves and where it moves within the body.  ***WHAT do you need to know??  **”The laws of basic fluid dynamics dictate that fluid flows from an area of high pressure to an area of lower pressure until equilibrium is reached.

 *The net effect :10% of fluid is left out of capillaries and returns via the lymphatic system.  *If the lymphatic system is not normal, there will be problems.  Positive feedback loop: example>  “The effect of lymphedema on the blood vessels causes a proliferation of new small blood vessels and the development of arteriovenous anastomoses. These new small vessels may leak as a result of abnormal changes in total tissue pressure in the lymphedematous region, further overloading the area.”

 **The anatomy of the lymphatic system is a regional one.  **”Lymphotomes” (lymph drainage territories) are separated by “watersheds”.  **Normal drainage is away from watershed; there are numerous collaterals.  **See p. 649 to view a simplified picture of drainage system.

 A. Lymphedema  1. Definition: swelling of the soft tissue that results from the accumulation of protein rich fluid in the extracellular spaces CAUSED BY decreased lymphatic transport capacity AND/OR increased lymphatic load

 2. Classification: Primary (idiopathic) or secondary (acquired)  Other terminology: primary was previously referred to as “connatal” if present from birth, “praecox” if at puberty, “tarda” if after age 35.

 Refer to Box 13-1  Stage 0> latent lymphedema> transport capacity is reduced, no clinical edema present  Stage 1> Accumulation of protein rich, pitting edema; reversible with elevation; may be normal size in morning; increases with activity, gravity dependent position, heat and humidity

 Stage 2> accumulation of protein rich, non- pitting edema with connective scar tissue; irreversible; does not resolve overnight; clinical fibrosis is present; skin changes present toward the end of stage 2  Stage 3> Lymphostatic elephantiasis > significant increase in connective and scar tissue; severe non-pitting, fibrotic edema; atrophic changes such as hardening of dermal tissue, skin folds, hyperkeratosis, leaking lymph fistulae

 3. Etiologies  Primary> unknown  Secondary> damage to otherwise normal lymphatic system  *Most common cause (worldwide, but not in USA)> filariasis> parasitic infection  *Most common cause in USA> regional lymph node dissection, radiation, reconstruction and a combination of these procedures  *Also caused by injuries, particularly when there is skin damage

 4. Pathogenesis>due to inadequate lymph transport, increased load (one of these or both)>>worsened by infection and/or wound healing process  Lymphedema> dilated vessels> incompetent valves> increased fluid into tissue>>lymphedema

 5. Clinical Manifestations>Signs and symptoms due to the impact of edema on lymphatics, body tissues and blood vessels  *secondary lymphedema is not considered reversible and can have an onset immediately post-operative (post trauma), or even weeks, months, years after surgery (trauma)  Symptoms: “full”sensation, sensation of skin tightness  Signs: edema, decreased flexibility, difficulty fitting into clothing in a specific area (watch, ring)

 6. Treatment (medical)  *If due to cancer, MD treats the cancer first  *Otherwise, no effective medical options have been identified (other than physical therapy)  *Left untreated, it is a progressive condition

 **To treat a patient with lymphedema, a physical therapist needs to have extra training to conduct these specialized techniques  Some interventions include: manual lymphatic drainage (MLD), short-stretch compression bandaging, exercise, compression garments, education, compression pumps and psychological and emotional support

 B. Lymphadenitis  Infected lymph node- lymph nodes are enlarged, warm, reddened  Treatment is focused on treating the underlying problem (infection)

 C. Lymphangitis  Acute inflammation of subcutaneous lymphatic channels from local process (infection, trauma, wound)  First noticed as a red streak under the skin radiating toward the regional lymph nodes  Systemic manifestations: fever, chills, malaise, anorexia  Treatment: correct diagnosis, antibiotics, appropriate wound care and infection control techniques

 D. Lipedema  Symmetrical swelling due to increased deposits of subcutaneous adipose tissue  NOT a disorder of the lymphatic system; needs to be differentially diagnosed

In Collaboration with Sean M. Collins PT, ScD