What is Lymphedema? - Healthy And Diseased Lymphatic Systems

TL:DR: A normal and well-functioning lymphatic system will transport the amount of lymphatic fluid produced by the body at any given time.  The typical amount of lymphatic fluid that is required to be transported from the periphery back to the circulatory system is well below the maximum capabilities of the lymphatic system.  When some form of injury is sustained and lymphatic fluid increases, for a short time the lymphatic system can be overcome by the volume of fluid that requires transport.  This results in swelling.  In some disease processes, such as congestive heart failure, the base amount of lymphatic fluid produced is increased above the transport capacity of the lymphatic system which results in chronic swelling.  In other cases, the lymphatic system may be diseased since birth, or have been injured and unable to repair itself, which reduces the maximum transport capabilities of the lymphatic system.  These impairments will lead to an overload of lymphatic fluid as well, though it is of a different nature than other forms of swelling.  Due to the nature of this fluid, it begins a cyclical process that continually increases the amount of fluid that is demanding transport back to the circulatory system.  This type of edema continually increases, and so does the size of the body that is affected by it.  Any kind of chronic edema can lead to wounds and infections, as well as the side effects that these may cause.

The Healthy Lymphatic System

A normal, well-functioning lymphatic system, has the ability to transport the naturally produced amount of lymphatic fluid.  Normal blood flow will produce lymphatic fluid, and any increase in blood flow will result in an increase in lymphatic fluid production.  In a healthy circulatory system, approximately 90% of the fluid that diffuses into the tissues is reabsorbed into the capillaries.  The 10% that remains is call Lymph.  The amount of lymphatic fluid being created and needing to be transported out of the tissues is called the lymphatic load (LL).  The amount of fluid that is being transported out of the tissues back to the circulatory system is called the Lymph Time Volume (LTV).  The peak LTV is called the Transport Capacity (TC).  In a healthy lymphatic system, LL is equal to LTV and LL is less than TC. (see figure 1)

Healthy Lymphatic System Response to an Injury

Most people have encountered swelling (edema) of some form or another in their lifetime.  Most people are familiar with swelling caused by an injury.  When this happens, the lymphatic load increases as the blood flow to the injured area increases.  In this situation LL rises until it surpasses TC and the result is swelling.  Because the injury is not permanent, the swelling will not last forever.  Once the blood flow reduces and LL begins to drop, TC will eventually overcome LL and the swelling will reduce.  This type of LL is referred to as high output failure, or dynamic insufficiency.  This type of swelling is characterized by low protein content (1). (see figure 2)

Healthy Lymphatic Response to Disease Processes

Another form of swelling can occur when the internal pressure of the veins increases, not allowing fluid to reabsorb into the circulatory system.  This is known as venous stasis.  It is caused when the valves within the veins begin to fail.  The result is an increase in pressure at the level of the lowest intact valve, or the foot/ankle if all the valves have failed.  Think of the pressure on your eardrums when you are at the bottom of a swimming pool.  That same type of pressure is pushing outward from within our thin-walled veins and results in less fluid being reabsorbed.  This is another form of high output failure.  It is easily distinguished from lymphedema and injury-induced swelling because of the classic staining of the skin a deep red or brown color, called hemosiderin staining.  In these cases, the LL has exceeded the TC and will likely never fall below TC again. (see figure 3).

  Heart and kidney failure tend to have similar mechanisms that cause swelling.  In heart failure the heart cannot pump the amount of blood out that is being brought in.  This bottleneck results in increased pressure behind the area of failure.  If the heart failure is of the left ventricle, then fluid can back up in the lungs first causing pulmonary hypertension and often producing phlegm that is tinged red or pink.  If the failure is of the right ventricle, then the fluid can back up in the peripheral veins, typically in the most dependent area of the body: the legs.  Either form of backup can eventually become systemic which results in increased pressure throughout the system.  If the left ventricle fails and causes an increase in pressure in the lungs, then the right ventricle cannot push fluid into the lungs, which results in the right side backing up and increasing pressure in the peripheral veins.  If the right ventricle fails and causes an increase in pressure of the peripheral veins, then the arteries cannot push blood through the circulatory system, which also becomes backed up.  This increases the difficulty of the left ventricle expelling blood, which will cause a backup in the lungs.  In either case, the increased pressure in the limbs will result in poor reabsorption of fluid, thus causing swelling.  In kidney failure, the toxins, waste and electrolytes are not filtered out properly.  Because water is required by our body to properly dilute blood and urine, the kidneys will not be able to expel excess water either.  This results in fluid retention throughout the circulatory system which also increases pressure in the veins, and thereby causes swelling.  In both these cases LL exceeds TC. (see figure 3).  When these two conditions are combined, the body has difficulty expelling fluid because the kidneys are failing and not filtering out toxins and minerals correctly.  This leads to an increase in blood volume, which puts greater stress on an already failing heart to pump out more fluid than it is already struggling to pump.  Both of these conditions in combination lead to greater edema that can be in the feet, up the calves, in the thighs and even rise into the abdomen and chest, in which case it would likely involve the hands and arms as well.  Both of these conditions are often treated with diuretics (“water-pills”), though these can be hard on the kidneys and are usually carefully regulated in people with kidney failure, if they are appropriate at all.  The complication that can arise, is that the diuretic is sometimes being used to treat the swelling, but it cannot directly treat the swelling, it can only indirectly treat it.  Swelling occurs in the peripheral tissues, the skin, essentially.  Diuretics only affect the fluid that is in your circulatory system, the blood vessels.  While too much fluid in the circulatory system can prevent your body from removing the fluid that is causing the swelling, in many cases the lymphatic system is already having problems moving the fluid because of the sheer volume present.  In this case, too much diuretics can be counterproductive, because at the capillary level there can be an increase in water that is removed from the periphery, which only serves to concentrate the minerals and proteins in the periphery, making it difficult to move.  This often results in edema that pits when pressure is applied to the area.  The outcome can be a body that is dehydrated in the circulatory system and full of fluid in the peripheral tissues with lack of ability to effectively remove that fluid from those tissues. 

Diseased Lymphatics

With lymphedema we find a different mechanism of action.  In lymphedema the lymphatic system is injured in some way.  Lymphatic tissue does not, in general, regenerate.  That is, once a lymph node is injured or removed or a lymph vessel is damaged, they will not regrow and return to normal function.  This injury causes TC to be reduced.  It will not necessarily increase LL, because the mechanism of injury can range from surgery or injury (which will cause an increase in LL) to genetic or inherited factors (which likely will not cause an increase in LL).  In cases of severe obesity, pressure around and on the lymphatic system can be so great that its ability to move lymph is impeded and blocked.  In all these examples, this reduction in TC causes a risk for developing lymphedema, and is in fact considered Stage 0 lymphedema.  If TC drops below the level of LL, this is when swelling begins.  Because TC has dropped permanently below the level of LL, swelling will continue to increase indefinitely. (see figure 4).

Stemmer’s sign(1) is a good diagnostic tool for lymphedema.  It is performed by lifting and pinching the skin on the back of the hand, finger, foot or toe.  If the skin lifts and pinches easily it is negative, if it does not lift and pinch it is positive.  A positive Stemmer’s sign is an indicator of lymphedema, but a negative Stemmer’s sign does not rule out lymphedema.

Stages of Lymphedema(1)

Lymphedema is characterized in stages, as already indicated.  There are 4 stages of lymphedema, they range from stage 0 through stage 3 as noted below:

• Stage 0: Known as the “latency” phase, there are no signs present in this phase, though symptoms may range from none to a feeling of fullness, heaviness or puffiness in the affected area.

• Stage 1: This is the “reversible” stage and is characterized by pitting edema* that can be treated with elevation of the affected area.

• Stage 2: The “spontaneously irreversible” stage is present when elevation of the affected area no longer reduces the swelling.  The swelling in this stage is described as “hard” compared to the “soft” swelling of stage 1.

• Stage 3: The worst and most debilitating stage of lymphedema, known as “elephantiasis”.  This stage is widely variable in severity, but can lead to great disability.  It is characterized by “hard” swelling, just as in stage 2, but also includes skin changes (which can manifest in stage 2) and lobule formation.

*Pitting edema is characterized by a temporary “pit” or indentation being formed when you squeeze or press on an area containing swelling.  Pitting is not exclusive to lymphedema.

Lymphedema is different from normal edema because of how high the protein content is.  In swelling that occurs from an injury, surgery or the aforementioned heart or kidney failure, edema is generally low in protein content.  The high protein content seen in lymphedema causes fibrosis.  Fibrosis is a process of laying down a dense collagen fiber network, similar to a scar.  This fibrotic tissue becomes thick and hard.  Where once pitting may have occurred in a lymphedematous region, after it has become fibrotic it will no longer pit.  This high protein content leading to fibrosis is what causes lymphedema to be so stubborn to control.  Because the protein content is so high, water is constantly attracted to the area.  More water means more edema, and more edema draws in more protein, which draws in more water, and the cycle continues on and on.  The more static protein that is in the area, the more fibrotic tissue that is laid down.

One of the major complications that can occur with lymphedema is cellulitis.  Cellulitis is a bacterial skin infection that causes pain and redness with localized swelling.  It is typically caused by cuts and scrapes that are not kept clean and dressed.  In addition, cuts and scrapes are slow to heal because of the excess fluid in the region that uses the break in the skin as a means to escape, leading to dripping or weeping wounds.  Because people with lymphedema already have trouble combatting fluid overload in the tissues, the increase in fluid rushing to the infected area only serves to exacerbate the problem.  Antibiotics are the typical treatment for cellulitis.  The trouble with this approach is that the lymphostatic fluid in the infected region greatly inhibits the antibiotic’s ability to combat the harmful bacteria.  Think of a traffic jam because of an accident with all lanes blocked.  The emergency vehicles need to make it to the scene of the accident, but can’t, or have a very difficult time doing so, because of the traffic congestion.  In order to allow the right people to get to the place they are needed, traffic in front needs to find a way to get around the accident, which will allow all those behind them to move up and follow them around the accident.  The same is the case with lymphedema.  If we have a case of cellulitis in the lower leg, but lymphedema is present up to the thigh, then the thigh needs to be addressed to allow the fluid farther down to move up, and the lower leg needs to be addressed to allow the antibiotics to do their work.  The methods for accomplishing this will be covered in the next blog post.

Thank you all for reading. I hope that this was informative.  If you have any feedback or questions, please feel free to contact me at thelakelapts@gmail.com. 

All the Best!

1.       Földi Michael, Földi Ethel, K. Strössenreuther Roman H, & Kubik, S. (2012). Lymphostatic Diseases. In Földi's textbook of lymphology: For physicians and lymphedema therapists. essay, Elsevier Urban & Fischer.