Mediastinal lymph node visualization in the absence of intrathoracic disease.

Abstract

Ever since Kinmonth (1) established a practical method for visualizing lymph nodes in man, numerous articles have been published, but few references have been made to the opacification of thoracic nodes by means of peripheral lymphography. In each published instance (5, 9, 11), the authors assumed that the occurrence was due to some pathologic process or to an anatomical abnormality. This paper presents three cases in which opacification of the thoracic nodes was not due to pathology. One of the limitations of peripheral lymphography is the failure to demonstrate certain node groups. For the investigation, staging, and treatment of many malignant tumors, evaluation of the thoracic nodes would be extremely valuable if a simple method of doing so could be devised. The study of normal and abnormal cases in which this has occurred incidentally may provide information of value in this regard. In our routine technic of lymphography, the inguinal, iliac, and para-aortic nodes are visualized with ease. These, however, drain into the thoracic duct, which in most cases arises at the level of L1 or L2, and from there until termination of the duct very little information can be obtained as to the condition of the thoracic lymph nodes. In reviewing our own cases, we observed that in most instances the thoracic duct could be demonstrated whenever the study was technically satisfactory and whenever no major replacement of nodes had occurred. Some authors feel that the visualization of the thoracic duct should be a warning of a too high injection rate (4), but in our experience this has not been a source of complications. It was also noted that not infrequently there was opacification of the left supraclavicular nodes. This last observation is of some importance in the discussion of our three cases. Anatomy The lymphatics from the lower limbs, pelvis, and abdomen, as well as those from the gut, drain into the thoracic duct. The thoracic duct arises at the level of the second lumbar vertebra and extends to the root of the neck, where it usually terminates at the junction of the left sub-clavian and jugular veins. Its origin in the abdomen is from a triangular dilatation called the cisterna chyli, which lies anterior to the vertebral body and to the right side of and posterior to the aorta. Within the thorax, it is located to the right of the aorta and anterior to the vertebral column; later it passes behind the aortic arch and the thoracic part of the left sub-clavian artery, entering the neck, where it arches laterally about 3 to 4 cm above the clavicle, crossing anteriorly to the left subclavian artery and then going on to its termination (6). The thoracic duct usually has only two valves, one at its origin and one at the junction of the left subclavian and jugular veins. During its passage through the mediastinum, the thoracic duct receives tributaries from the intercostal nodes.