Q: My lymphoscintigraphy (LAS) results were interpreted and I was told that I have no lymph vessels in my legs. Can this be true?
A: No, this cannot be an accurate interpretation of your results, but rest assured, many patients have echoed your comments "precisely" in my experience. LAS measures uptake and transport of lymph over a period of time. A radioisotope, which can only be absorbed by lymphatics due to its molecular size, is injected into the system, usually at the toes, and diffuses into the swollen tissues. Radiological pictures are taken to mark the progression of the radioisotope over time.
I would first like to comment that sometimes LAS test results are misinterpreted simply due to the medical profession's inexperience performing this particular test. There are very few physicians who specialize in lymphology, much less call for routine LAS for his/her lymphedema patients. As such, it is quite unlikely that any patient would find a local facility specialized in providing this test, which is then followed by informed interpretation of the results.
Oftentimes, as so many of us realize, lymphedema as a disease condition is mislabeled and misunderstood. Commonly, whole batteries of tests are conducted to rule out other disease conditions including: deep vein thrombosis (DVT), heart disease (such as Congestive Heart Failure [CHF]), cancer, and liver failure, to name a few. Most would agree that it is prudent to run these tests to rule out serious additional health concerns and, once other problems are dismissed, lymphedema is generally considered a diagnosis of "exclusion" (everything else that could cause swelling has been ruled out).
One of the greatest problems encountered is that there are no agreed upon standards for administering LAS such as: time interval between injection to first image; second image and last image; amount of activity (movement/ exercise); type and duration of activity during periods between imaging, etc.
Another problem is that, unlike MRI, CT scan and dye injections, LAS does not provide a clear, resolute picture, but rather, shows a hazy image that requires a trained eye to interpret.
So why would you be told that there are no lymph vessels in your legs? The answer, again, becomes a matter of interpretation. When the injection is performed, a radioisotope, which can only be absorbed by lymphatics due to its molecular size, diffuses into the swollen tissues. Since lymphedema involves "stagnant" tissue fluid and poor transportation of lymph, it stands to reason that the injected solution would give a picture of little to no movement (i.e. Haze).
Furthermore, everyone has lymph vessels throughout the body since to be born without them would render the human being lifeless. In primary lymphedema, we know that, most often, less vessels and nodes exist and that the size/ caliber of these tissues is smaller than normal, therefore less uptake of lymph is seen and transport is sluggish. In secondary lymphedema, usually the lymph nodes are either damaged or removed causing many blocked connections from the vessels that were attached. In either situation, lymph vessels do indeed still exist; however, their function may be quite inadequate. If sufficient time is not taken during the LAS to record movement of tracer, then one could conclude that no vessels are working. However, in all cases, even when sufficient damage has been sustained, the lymphatic system is laboring to transport fluid wherever healthy vessels still exist. Perhaps two hours after the injection has been performed, tracer will be seen in other body areas indicating that it has made its way into the bloodstream via the thoracic duct.
It is important to address this misconception to clarify that lymphedema is nearly always treatable. It remains treatable even in the most advanced cases due to the ability of our lymphatic system to be "re-awakened" with proper stimulation, and to work more efficiently and effectively. Manual Lymph Drainage (MLD) has been shown to make vessels contract more frequently, thus propelling fluid through once fatigued vessels. Exercise within a compression bandage further stimulates vessel activity. So to be clear, vessels always exist, but they may not be visualized by LAS because LAS measures uptake of fluid and transport over time.
Q: I received an LAS and it was determined that my lymphatic system was functioning perfectly, yet I do have lymphedema. How can this be true?
A: This is an excellent question. What it indicates is a "false negative" reading which occurs with some frequency in LAS testing. Remember that LAS measures uptake and transport of lymph over a period of time. This time period is usually in the realm of minutes rather than hours so that, in a normal system, it is possible for lymph to reach the groin from the injection site (between the toes) in approximately 25 minutes. In most cases of lymphedema, LAS would provide a picture of stagnancy, which appears as a hazy outline of the limb since contrast substance is diffusing uncontrollably into the tissues. However, it has to be noted that the lymphatic system does not simply "shut down" altogether. Actually, there will be portions of the vessel network that are laboring to soak up this fluid at a much higher rate than is possible in more diseased areas. This "quickening" of lymph vessel workload is know as the "safety valve function" and is a wonderfully adjustable element similar to the cardio-pulmonary system whereby the heart adjusts its rate and amplitude of contraction when demanded to supply more oxygenated blood to body areas.
In this lymphedema scenario, it is possible for injected contrast to be quite rapidly absorbed into some of these highly active vessels and, as such, show a "clinical picture" of normalcy. Certainly, it is important to keep in mind that lymphedema is most often a clinical diagnosis, relying upon skilled assessment including history, visual features, and palpable (textural) presentation more than any other factors.
Another potential test that may indicate a false negative finding is called the Stemmer Sign. This test measures the textural change or skin thickening in the skin of the toes to verify whether or not protein rich fluid is stagnating in this area. Since lymphedema usually starts in the area farthest from the trunk, the toes and fingers are classically the first areas to show textural changes. The interesting fact however, similar to the false negative LAS reading, is that sometimes lymphedema chooses to spare the foot and toes, rendering a negative Stemmer sign. One must only look above the foot to see positive traits of lymphedema.
Steve Norton, CLT-LANA, is Director of The Norton School of Lymphatic Therapy, www.nortonschool.com.
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