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EDUCATION EXHIBIT |
Virginia Vascular Center and Virginia Radiology Associates, Manassas, Virginia
A couple of questions come to mind: (a) Can anyone remember the last time lymphangiography was performed in your department? I would hazard a guess that you can probably count on two hands the number of times this procedure has been performed in the past decade. (b) Would you remember how to perform lymphangiography and, more important, how to interpret the results if you were asked to do so tomorrow? These are difficult questions, but, judging from the preceding article 1), they may become more relevant in the near future. In patients with retroperitoneal and pelvic cancer, determination of local and regional lymph node involvement is an important prognostic factor and will determine treatment options for the patient 2). The knowledge of microscopic involvement and architectural distortion is rapidly becoming integral in the decision making for the proper treatment of a variety of oncologic patients.
Lymphangiography has become a dying art form in angiography suites across the United States. Fellows and residents in academic medical centers in the United States and around the world for the past decade or more have been poorly trained in how to perform and interpret lymphangiography, mainly due to the low numbers of requests for the procedure 3). Unfortunately, there are many interventional radiologists who graduated from their fellowships without ever having seen lymphangiography performed or interpreted. When the procedure is requested, it usually falls into the hands of one of the senior members of the angiography team, often followed by a disheartened groan or sigh. The procedure is tedious to perform, and cannulating a lymphatic on the dorsum of the foot takes keen eyesight and a steady hand in order not to puncture or tear the lymphatic. There is hardly a more frustrating event than to spend a significant amount of time freeing up the lymphatic from the surrounding fascia and adipose tissue only to tear the vessel in a matter of seconds trying to cannulate it with a lymphangiography needle.
Guermazi et al 1) make a compelling argument that microscopic disease, which can collect and distort the internal architecture of a "normal-sized" lymph node at cross-sectional imaging, makes a large difference in treatment planning for a variety of cancer patients. Also, the accumulated lymphangiographic contrast agent can be used to follow the success or failure of the given treatment options. In a recent study of patients with cervical cancer who underwent surgery and lymph node resection, lymphangiography was found to have a positive predictive value of 74% for pelvic node metastases, 73% for common iliac node metastases, and 88% for paraaortic node metastases. Also, a negative predictive value of 76% for common iliac node metastases and 77% for paraaortic node metastases was found 4). The lymphangiographic findings led the clinicians to extend the radiation fields to include the paraaortic adenopathy. Also, lymphangiographic contrast material within pelvic nodes has been shown to be superior to bony structures as a landmark for external-beam irradiation 5). Variant anatomy is better delineated with lymphangiography, thus allowing more accurate treatment.
There is a significant amount of imaging research devoted to finding alternative techniques in the hope of noninvasively visualizing the lymph node architecture. One promising area of research involves ultrasmall superparamagnetic iron oxide as a lymphatic contrast agent 2,6). Use of this contrast agent and the MR lymphangiography technique may prove beneficial in differentiating benign from malignant lymph nodes and providing information on nodal morphology, bringing cross-sectional imaging one step closer to determining microscopic involvement of lymph nodes.
Investigators have also begun attempting to visualize mesenteric adenopathy in patients with unresectable hepatobiliary pancreatic cancer by using percutaneous transhepatic lymphangiography 7). Visualization of the adenopathy is fairly rapid. The hope of the authors is to use this technique to deliver chemotherapy in a targeted fashion in an attempt to treat the metastatic adenopathy. This is a fairly slick access technique to deliver targeted chemotherapy. One can only postulate that the lymphatics of the legs can be used in a similar fashion to deliver targeted chemotherapy to pathologic pelvic and paraaortic lymph nodes. Perhaps another area of research potential... .
There has been a significant amount of literature in the recent past concerning the treatment of traumatic injury to the thoracic duct with embolization 8–11). This technique is possible only with use of pedal lymphography. There is a likelihood that this procedure will become more prevalent in trauma centers and busy thoracic surgery centers for this type of clinical problem. Interventional radiologists need to become more familiar with the technique of pedal lymphography for the possible future need for these types of embolization procedures.
Use of pathologic size criteria based on noninvasive cross-sectional imaging may be misleading to our referring clinicians. At the present time, cross-sectional imaging does not allow differentiation of benign enlarged adenopathy (ie, reactive or inflammatory) versus malignant adenopathy. Also, as stated earlier, cross-sectional imaging cannot demonstrate architectural distortion due to a malignant process, which could alter the treatment strategy for the affected patient. I plan on disseminating the preceding article to the oncologists practicing in my hospital and will likely see a rise in lymphangiography requests in the near future. Is anyone selling a used Harvard pump?
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