Lymphatico-venous Communications
Present research has found clues about a lymphatico-venous communication. In mammals, lymphatico-venous communications other than those at the base of the neck are not easy to demonstrate, but described in some experiments.
The specialists observed that the pulmonary complications following lymphangiography (a test which utilizes X ray technology, along with the injection of a contrast agent, to view lymphatic circulation and lymph nodes for diagnostic purposes) are more often severe in patients with lymphatic obstruction. In these cases, the contrast medium is thought to reach the vascular system via lymphovenous communications which shunt the material directly into the venous stream, bypassing those lymph nodes distal to the communications, Because less contrast agent is absorbed in lymph nodes, a greater portion of the injected volume passes into the vascular system. Since pulmonary complications are related to the amount of medium reaching the lungs area, the early recognition of lymphovenous communications is a great significance to the lymphangiographer. Another "hint" in proving a lymph-vein communication is offered by a Robert F Dunn experiment. The passage of radioactively tagged tracers, injected at elevated pressure, through the lymph node-venous communications coincides with the increased pressures of injection and subsequent nodal palpation in dogs. The passage of iodinated I 125 serum albumen (ISA) indicates that direct lymph node-venous communications are present, whereas passage of nucleated erythrocytes requires a communication structure the size of a capillary or larger. Moreover, the evidence suggest that in mammals under normal conditions, mostly of the lymph is returned to the blood stream through the lymphatico-venous communications at the base of the neck. When the thoracic duct-venous communication is blocked, however, the resultant raised intralymphatic pressure will usually cause other normal non-functioning communications to open and thereby allow the return of lymph to the blood stream.
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