The lymphatic system is comprised of a series of vessels that collect all the interstitial fluid throughout the body and carry it through the thoracic duct into veins. Because the lymphatic system is solely responsible for removal of the proteins and interstitial fluid from the tissues, it is an active participant in any disorder that is associated with tissue congestion and edema. The lymphatic system consists of several organ subsystems (soft tissue, liver, intestine, kidney, etc.), each with a slightly different mechanism of lymph production and constitution of the lymph. Anatomy and communication between different subsystems is very complex and variable, and the lymphatic imaging techniques of lymphatic flow disorders for each system are unique.
This complicated anatomy has made the lymphatic system historically difficult to image and has resulted in a lack of interventional options. Despite its importance, these challenges have largely pushed the lymphatic system off the radar of modern medicine.
Recent development of several lymphatic imaging techniques (such as intranodal lymphangiography, dynamic contrast-enhanced MR lymphangiography and liver lymphangiography) resulted in discovery of the pathological mechanisms of a variety of disease processes. Percutaneous lymphatic interventions over the decade expanded from one procedure—thoracic duct catheterization and embolization—to several that include interstitial lymphatic embolization, liver lymphatic embolization, thoracic duct stenting and externalization.
With IRs’ technical expertise, our imaging modalities and minimally invasive procedures, we are well positioned to map the lymphatic system, locate abnormalities and treat the root cause of a variety of symptoms.
Science fiction come to life
During my last year of radiology residency at Rabin Medical Center in Israel, I read a paper by Constantin Cope, MD, FSIR, about a new lymphatic procedure—thoracic duct embolization. It was designed as a minimally invasive alternative to surgical thoracic duct ligation to treat postsurgical chylothorax. I was amazed by the article, which almost felt like science fiction.
Two years later, I started my fellowship at the University of Pennsylvania and was able to work alongside Dr. Cope learning directly from the master. In those days, the procedure took up to 9 hours to complete and was an exhausting endeavor. However, I was hooked and infected with the bug of lymphomania.
Since my time with Dr. Cope, I’ve continued discovering this field that was previously unknown to me and I’ve begun investigating how lymphatic complications can contribute to the symptoms of other, seemingly unrelated conditions. Reading old lymphatic research papers, I realized that there is a huge potential to look into the pathophysiology of diseases from completely different perspective—we just need better tools.
Currently, 10–20 diseases are considered to be within the lymphatics space. With increasing interest and research, though, I believe lymphatic intervention could play a role in treating 200 or more diseases.
Using new advanced imaging technology, we now are able to provide much better treatment for traditional lymphatic intervention conditions such as chylothorax. The 9-hour procedure I studied with Dr. Cope can now be completed in under an hour. Development of interstitial embolization techniques has allowed us to expand in the lymphatic territories beyond the thoracic duct and provide new approaches for conditions such as chylous ascites, lymphocele, a variety of lymphorrhea conditions and genital edema.
Application of new imaging modalities also allows us to discover new diseases. One example is plastic bronchitis, a relatively rare condition in which abnormal circulation causes lymph fluid to build up in airways and solidify into casts, which result in suffocation and pulmonary insufficiency. Using minimally invasive imaging advances such as intranodal lymphangiography and dynamic contrast-enhanced magnetic resonance lymphangiography, the abnormal flow can be located and treated by percutaneous transabdominal catheterization and selective lymphatic duct embolization.
The future of lymphatics
When most physicians think of lymphatic flow disorders, they think of lymphedema or swollen lymph nodes, primarily because these conditions are visible to the human eye. Currently, 10–20 diseases are considered to be within the lymphatics space. With increasing interest and research, though, I believe lymphatic intervention could play a role in treating 200 or more diseases.
In February, SIR Foundation’s Clinical Research and Registries Division supported a research consensus panel (RCP) focusing on lymphatics. I was invited to be lead investigator, and our goal was to discuss the needs of the lymphatics field and determine the top research priority topics. I was joined by a variety of interdisciplinary experts in fields such as cardiology, pulmonology, urology and vascular surgery.
The RCP highlighted how complications of the lymphatic system can impact the whole body and how—by working closely together—IRs and lymphatics experts can further understand the lymphatic system and further improve patient care. I believe there is ample opportunity for such partnerships in the future between lymphatic IRs and other specialties like cardiology.
During the RCP, we decided to prioritize projects such as congestive heart failure and lymphatic decompression (external vs. internal); detoxification of the thoracic duct lymph for acute illness (drainage vs. drugs); development of newer agents/techniques for lymphatic imaging; determination of lymph composition to predict origin of lymphatic to allow therapy and predict outcomes; lymphatic interventions to treat ascites secondary to cirrhosis; lymphatics drug delivery for the treatment of lymphatic diseases; and analysis of lymph composition to determine the source of the fluid.
The value of collaboration
Further research and collaborative partnerships will only help our field grow and provide the interest needed for us to expand—specifically in terms of developing specialized equipment suited to our needs. That is, there is a need for more refined technology better suited to navigating lymphatic vessels vs. arteries/veins. Developing this technology requires evidence that the field can support the cost of design, though, because the market is currently so small. However, the volume of lymphatic cases I see is constantly growing, and so is interest. I believe that industry will follow.
In conclusion, spreading awareness and forging partnerships with other specialties will not only advance lymphatic research but showcase the value of IRs’ imaging capabilities in providing ground-breaking, quality patient care.
